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Scale models of gravel bed rivers Parent, Alain Paul 1988

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SCALE  MODELS  OF  GRAVEL  BED  RIVERS  By  ALAIN B.Sc,  University  THESIS OF  PAUL  THE  PARENT  de  SUBMITTED  Montreal,  IN  REQUIREMENTS MASTER  PARTIAL  FOR OF  THE  1985  FULFILLMENT DEGREE  OF  SCIENCE  in  THE  FACULTY  OF  Department  We  accept  this  the  THE  GRADUATE of  UNIVERSITY  OF  September (c)  Alain  Geography  thesis  required  Paul  STUDIES  as  conforming  standard  BRITISH  COLUMBIA  1988 Parent,  1988  to  In  presenting  degree freely  at  this  the  available  copying  of  department publication  of  in  partial  fulfilment  University  of  British  Columbia,  for  this or  thesis  reference  thesis by  this  for  his thesis  and  scholarly  or  her  for  Geography  The University of British 1956 Main Mall Vancouver, Canada V6T 1Y3  Columbia  September 1, 1988  I further  purposes  gain  the  requirements  I agree  shall  that  agree  may  representatives.  financial  permission.  Department of  study.  of  be  It not  is  that  the  Library  permission  granted  by  understood be  for  allowed  an  advanced  shall for  the that  without  make  it  extensive  head  of  my  copying  or  my  written  The  combined  gravel-bed  river  studies and  demonstrated  the  well  as  potential  in  fluvial  the  flow  An  of  extension  the  as  is  a  if  which  of  intermediate  used as  would  study  viewed  benefit  herein  prototype  (field)  river  for  appraisal  of  of  was model  of  detailed case  of  for  shear  elements  consisted  The  demonstration  the  the  in to  ubiquitous  such  of  satisfied.  research  demonstrated  performance.  level  family  river  methodology. need  stress  of  samples.  same  the  revealed  stress  according  the  but  such  flows  also  shear  are  Known  from  roughness  Knowledge  part  vehicle  poorly  investigation  framework  as  a  a  as  research  material  specific  conditions  a  rivers.  on  as  have  quantitative  bed  crucial  variability  relative  surface  model"  performed  the  concepts  profiles,  a  size  similitude  velocity  in  full  model  for  comparison  a  small-scale  scaling  and  are  gravel-bed  the  of  in  This  "generic  some  presented  laboratory  appraisal  models  processes  sequence,  phenomenon The  the  scale  strict  systems  ones  pool-riffle herein,  the  of  laboratory field  of  structure  laboratory  proposition  which  of  comparison  measurements,  processes  associated  applicability  the  and  its  flow  geomor p h o l o g y .  considered  field  of  as  for  an  estimates  in  field  history to  be  of  size the  important  Table  of  contents  Abstract  Table  i i  of  contents  List  of  t a b l es  List  of  figures  List  of  symbol s  iii  vii  v i i i  xv  Aknowledgments  xv i i  1  1.0  I ntroduct ion  2.0  Scale  2.1  Generalities  8  2.2  S imi I i t u d e  9  2.3  Dimensional  models  of a l l u v i a l  analysis  and  8  rivers  the  development  of  scaling  iv  2.4  Froudian  2.4.1  scaling  Natural  stream  (hydraulic  2.4.2  2.5  Criteria  for  of  mode Is  scale  The or  2.5.2  The  closer  test  roughness  and  stress  of  a  range  behaviour  of  scales 18  geometry  of  the  frictional  plot  21  representativeness  characteristics  length  of  excess  Reproduction  Generic  of  over  channel  results)  hydraulic  reproduction  tions  2.5.3  a  natural  behaviour  reproduction of  and  geometry  Decons t r a i ned  2.5.1  2.6  laws  24  sediment  entrainment  condi-  stress  flow  30  patterns  and  bed  shear  distribution  modelling  concept  32  and  geomorpho1ogica1  research  33  3.0  Field  36  3.1  Site  3.2  Bed  study  selection,  material  location  sampling  and  description  36  42  3.3  Measurement shear  instruments  and  estimation  of  stress  3.4  Results  3.5  Problems  4.0  Laboratory  4.1  Flume  from  Scale  45  flow  raised  study  measurements  by  field  and  description,  measurement  4.2  set-up,  52  measurements  68  75  conformation  instrumentation  and  hydrodynamic  procedures  modelling  of  75  Blaney  4.2.1  General  4.2.2  Bed  4.2.3  Working  assumptions  4.2.4  Initial  experience  CreeK:  strategy  considerations  material  78  scaling  79  regarding  with  and  field  conditions.  adjustments  to  the  mode 1  4.3  Laboratory  4.3.1  Bed  84  88  results  morphology  and  their  conformation  conformation  to  field  92  4.3.2  Flow  measurement  4.3.3  Surface  bed  conformation  material  97  characteristics  and  confor-  mation  4.4  Extended  field  5.0  109  observations  and  laboratory  on  site's  characteristics  from  results  117  123  Conclusions  127  References  Appendix:  Bed  configurations  A.1  General  considerations  A.2  Bedform  classification  in  low  mobility  rivers.  139  and  conditions  of  pool-riffle  occur r ence  A.3  Flow  A.4  142  processes,  r i f f l e  origin  and  evolution  of  the  pool-  phenomenon  Pool-riffle  139  sequences:  147  perspectives  and  prospects..  151  vii  List  Table  of  1.  tab!es  Grain (in  size  mm)  Blaney  Table  2.  Mean and  distribution  for  selected  bed  material  diameters samples,  Creek  46  hydraulic 23,  percentile  1986  parameters  hydrological  of  November  events,  20  Blaney  Creek  Table  3.  Mean run  55  hydraulic 14  found  Table  4.  and from  Hydraulic run  15  and  geometric  comparison Froude  and  with  target  similarity  geometric  parameters values  principles  parameters  from as 98  for 1 22  vi i i  List  of  Figure  figures  1.  Grain  size  selected  versus  set  of  Figure  2.  Deconstrained  Figure  3.  Resistance  Figure  4.  The  Blaney  Figure  5.  CreeK  Topographic site  of  Figure  6.  Views  Figure  7.  Size  of  Blaney  geometry  plot  map  of  23  28 British  field  site  Columbia inset  and  location  Blaney  38  Creek 39  Blaney  at  23  location  Creek  distributions  samples  for  diagram  Forest:  field  plot  data  hydraulic  University  Research  discharge  of  downstream  Creek  field  bed  site  40  material  r i f f l e  site, 44  ix  Figure  8.  Comparison for  Figure  9.  grid  and  r i f f l e  sites,  Ott  Figure  10.  11.  12.  Figure  13.  Figure  14.  44  meter  rod48  20  and  Dimensionless area,  Dimensionless area,  area  in 23,  water 1986  velocity November  events  23,  54  1986  57  profiles,  23,  velocity  (lower  level,  profiles,  velocity  November  Dimensionless  1986  58  profiles,  stage),  November  1986  Local  58  variability  profiles, 23,  and  array  November  23,  pool  Creek  current  changes  pool  distributions  downstream  reach  Blaney  Temporal  pool  size  from  within  laboratory  r i f f l e  Figure  pooled  samples  r i f f l e  mounted  Figure  of  1986  station  in  velocity  L,  November ,  60  X  Figure  15.  Local  variability  profiles, 23,  Figure  16.  17.  Scans  Scans  Figure  18.  19.  20.  November  23,  1986  at  downstream  end  of  station  internal  21.  Near-bottom  Blaney  20,  Near-bottom  November  November  and  stations, 23,  1986  Blaney 1986  64  estimates  stations, 20,  1986  65  near-surface creek,  1986  and  23,  estimates  shear  sampling  Creek,  flowlines,  shear  November  internal  velocity  November  62  November  sampling  Creek,  flowlines,  Figure  W,  pool,  62  velocity  Blaney  Figure  of  V,  Near-bed at  end  1986  Blaney  Figure  November  downstream  Near-bed at  P,  60  at  r i f f l e , 23,  velocity  1986  station  Figure  station  in  66  near-surface creek, 67  xi  Figure  22.  Near-bottom flowlines, November at  Figure  23.  24.  Figure  25.  26.  bed  November  material  General  pool,  23,  gauge  view  sorting  Blaney  1986  Blaney  of  73  the  water  Department  of  Geography,  University  of  British  Comparison  of  laboratory  of  the  of  Blaney  the  scaled  truncated  Critical  to  the  of  Blaney  at  the The  Columbia  sediment  corrected size  76  and  non-  distributions  volumetric  sample  Creek  shear  graphical  73  Creek  flume  with  Creek  hydrological  recirculating  corrected  27.  (staff  69  proximal  mixture  Figure  1986  creek,  cm)  event,  Figure  near-surface  Blaney 23,  Lateral in  Figure  40  and  81  velocity-based  correction  truncated Creek  procedure  volumetric  sample 83  xi  Figure  28.  Lego-built bedrock  Figure  29.  30.  31.  Topographical  32.  Initial  Figure  33.  34.  Figure  35.  36.  map  of  run  13  final 93  map  of  run  14  final 94  final  conditions, 96  pool,  run  Dimensionless r i f f l e ,  velocity  100  velocity  100  of  velocity  Upstream  of  downstream  r i f f l e ,  velocity  part  of  profiles,  r i f f l e ,  Dimensionless  Dimensionless  profiles,  14  velocity  part  part  profiles,  14  run  Dimensionless downstream  Figure  87  14  over  Figure  and  Dimensionless in  Creek  configuration  run  Figure  Blaney  configuration  bed  Figure  of  outcrop  Topographical bed  Figure  model  pool,  run  14  101  profiles, run  14  101  profiles, run  14  102  xi i i  Figure  Figure  37.  38.  D i m e n s i o n 1ess  velocity  upstream  of  part  Figure  39.  shear  test,  d i m e n s i o n 1ess  41.  Figure  42.  43.  Size  104  shear  estimates  stations,  near-surface 14  distribution material  Grain  size  Grain  110  of  surface  samples,  run  distribution,  and  size  surface  44.  and run  final  surface  14  run  112  14,  materials  run  14  and  field  (scaled)  samples  115  Deviation  from  velocity,  maximum  values  pool  in  113  distribution  comparison,  Figure  velocity  106  initial  Figure  102  variability  sampling  Near-bottom  bed  14  14  flowlines,  Figure  run  14  internal  velocity  run  40.  stress  run  Near-bed at  Figure  pool,  Local  profiles,  profiles,  one-minute and  average  minimum 118  xi v  Figure  45.  Deviation  from  velocity,  maximum  values  over  one-minute  r i f f l e  and  average  minimum 118  XV  List  b  of  symbols  Hydraulic  geometry  (depth/discharge)  exponent C(j  Drag  coefficient  d  Mean  channel  Dj  Grain  size  diameter  percentiles f  depth  of  Hydraulic  (subscript  the  size  geometry  refers  distribution)  (width/discharge)  exponent ff  Friction  factor  F  Shields'  parameter  s  F^  Drag  Fg  Gravitational  Fj  Inertia  force  F  Viscous  force  v  g k  force force  Gravitational s  Equivalent  L  Length  Q  Channel  R  Hydraulic  Re  Flow  Rp  Particle  s  Submerged  acceleration sand  roughness  scale discharge radius  Reynolds  number  Reynolds specific  number weight  of  sediment  to  Energy  gradient.  Mean  flow  Average  velocity velocity  Particle  settling  Shear  velocity  velocity  Mean  channel  Local  flow  Function  of weight  Karman  Scale  width depth  Specific Von  fluctuations  constant  ratio  (prototype/model)  characteristic Dynamic  parameter  x  viscosity  Kinematic  viscosity  Dimensionless  number  Density Boundary  shear  Shields'  critical  stress shear  stress  of  Acknowledgements It is a great pleasure to express my most sincere recognition to my supervisor, Dr Michael Church, for his thoughtful guidance and his intellectual contribution which greatly helped the proper completion of this research project. Dr Church provided the framework to narrow my vast initial intentions to a project of a size appropriate to the Master's level. I would also like to thank Dr Douw G. Steyn for his comments and his support with intrumentation. I am also grateful to Dr Olav Slaymaker, to Dr Edward Hickin from the Department of Geography at Simon Fraser University and to Dr Michael C. Quick from the Department of Civil engineering of the University of British Columbia who kindly loaned their current meters for the field measurements. The help of Alastair Ross and Michel Lapointe during the field work (that means under very nasty conditions) was very much appreciated. Michel has also been a most interesting colleague to exchange with in Moliere's language. In the laboratory and in general, the help of and the interactions with John Wolcott were also a much appreciated stimulus. Discussions with my colleague David McLean were always lessons with intellectual fallouts. I am also grateful to the people at the U.B.C. Research Forest who provided equipment and support for the field work. Finally the help of Sylvie Lalonde in the field and with some of the figures is gratefully acknowledged. Financial support to the author was provided via a grant and fellowship from the Natural Sciences and Engineering Research Council of Canada.  xv i i i  The  Sands The  of River  Time of  were  eroded  Constant  by  Change  Introduction  1.0  Since  the  introduction  geomorphology, study  the  (Chorley,  behaviour  of  is  consistent  first  the  approach  increasing  of  into In  classical  textbook  of  main  contributions recognition  involving  stream  channels  into landform  insight  systems.  the  of  to  early  relationships  parameters  methods  those  the  geomorphology, scale  hydrodynamic  yielded  milestone  Amongst  to  functional  has  perhaps  (1964).  studies  quantitative  geomor phological  the  developments others  dominant,  1978)  geomorphology,  of  the fluvial  quantitative Leopold  of  of  and  functional some  fairly  morphological  and/or  has  utmost  been  of  interest. Empirical  methods  regarding  alluvial  questions  about  consequence, gave  way  developing  laws  immense episodic  the  empirical  process-oriented of  be  complexity and  lead  mechanisms  as  well  irregular  the  raised  which  were  functional  as  which  occurence  some  the of  crucial  involved.  were  However,  situation of  generalizations  approach  much  This size  those  also  behaviour.  developed. and  to  studies  stream  difficulties can  first behaviour  mainly  laws  considerable such  channel  the to  which  work  fluvial  gradually aimed there  ahead  results  In  at are  before  from  the  system,  the  geomor phologically  2  effective  events,  functions,  and  quantitative response  the from  of  the  consideration  to  space  and  Those  smaller,  Concurrently, subsequent  not  fulfill  of  problems  Church  limitations  of  sediment  digital  the  mean evident  (and  subject and  or  the  of fact  dynamics  detailed and  fluvial that  up  1978). to  concerning  popular  are,  could  to  for  observations,  in  over  has space particular  in  many  point:  for' and  estimation  the the  bring  emergence based  real  described  become and  of on  progress  Acknowledging be  of  mathematical  mostly  geomorphology.  it  understanding  a  the  since  can  could  usefulness  Also  not  flow  values  helpful  incidentally,  water  measurement  Average-value  the  rivers.  components,  structure  been  formulations  so  the  physical  reviewed  quantities),  fluctuating that  which  problems  system.  nature)  has  been  in  susceptible  hydrodynamic  have  gravel-bed  have  hydrodynamic  situation  flow  which  increased  Chorley,  appeared  fluvial  studies practical  in  of  complete  the  average-value  computers  average to  a  (1985)  fluvial  restricted  emerged:  of  transport  formulations,  rapidly  objective  river  instance,  the  system.  fact  of  in  by  more  relevant  average  of  govern  research  approach"  of  (mainly  which  of  subjects  treatment  in  forcing  representative  accompanied  systems  fluvial  features  formulations  obtain  scope  particularly  the  the  numerous  the  manageable  another  and  in  "realistic  some  of  their  system.  (the  to  to  of  parameters  necessarily  more  behaviour  the  geomorphological  time  insight  of  change  was  unsteadiness  difficulties  fluvial  the  geomorphology  the  the  measurements  Consequently,  bring  temporal  this by  its  increasingly time,  of  the  configurations  of  interest,  could  interactions  improve  amongst  phenomena  and  our  physical  river  the  understanding  hydrodynamics,  geometrical  of  sediment  the  transport  configuration  of  stream  boundaries. However,  detailed  sometimes is  impractical  due  to  mentioned  above.  to  scale)  models  to In a  some  reported  by  considered by  the  conditions others, The most  theory some  on  river  and  others,  1987)  of  physical  of  similarity,  aspects  of  this  of  to  has  Physical  (or  similarity  have  been  some  modelling, study  order  management. used  from  the  work  authors  have  consider  although  to  in  river  have  systems  studies  generally  instance,  river  situations:  field  theory  generally (for  and  conditions.  related  perspective  principles  to  engineering  models  difficult  geomorphological  the  problems  physical  Schumm the  in  specific  descriptive  of  alternative  based  are  full-scale  experimental  used  geomorphology, more  an  rivers  extensively  in  characteristics  under  of  measurements  perform  Hence,  work  solve  to  inherent  been  been  flow  as  prescribed  under  controlled  behaviour  (Southard  and  1980,1984). following  quotations  geomorphologists  summarize  regarding  physical  well  the  viewpoint  models:  " Scale modelling is essentially an empirical exercise whose value is limited in a geomorphic context by the extended spatial scales common to geomorphological problems. Despite the use of various modelling strategies, geomorphology remains essentially a field science." (Knighton, 1984, p.6)  of  " Although hardware models have been extensively used for descriptive and predictive purposes, they are inherently incapable of providing the last link in the chain of scientific investigation, the theory or the law." (Mosley and Zimpfer, 1978, p.450) The  bases  for  geomorphological In  a  as  reliable  of  too  The  as  similarity for  possible  theory,  must  formulated rivers  collection  that  of  used  not  solely  systematically about  river  applied  others  by  are  fluvial  in  some  conditions  to  be  on  the scale  to  provide  to  natural  too  general  geomorphology:  formal  of  reasoning  known  circumstances for  as  which  lead  if  as collect  dynamics.  to  the  a  and  of  this  a is  alluvial for  understanding to  river  framework physical  the  also  situation  behaviour.  models in  of the  provided  fundamental  laboratory  be  hydrodynamic  eventually  but  can  of used  alluvial  tools  analyze a  be  better  respected,  descriptive  Once  can  theoretical  be  models  and  theories  similarity  scale  herein  quantitative  rivers  or  studied  principles of  in  laws  formulated, of  similarity  would  development  concept  range  analysis  processes  the  and  Undistorted  on  mechanical  Otherwise  used  hypothesis  and  measurements  be  exposed.  consider  present  quantitative  be  follows.  constructed  Schumm  many  remark  also  at  for  formally  but  can  hold  established.  the  as  (1987)  supported  The  be  Consequently,  is can  research.  others  science  restrain  which  not  which  of  may  however  models  a  results  to  modelling,  tool  physical  statements  which  and  inexact  susceptible  scale  were  Schumm  quantitative  systems. and  book,  advantages  modelling  statements,  situations,  recent  various  such  can order  by be to  observations is  shown  to  be  similar  collected A  to in  the  the  natural  current  model  strategy  controlled  conditions.  appropriate  generic  model the  mainly and  conditions particular  guided  choice  the  represents field,  size in  (especially  the  grained  relatively alternative  a  the bed  performed  state  scaling  of  is  often  met  most  length size  rivers  scales distribution  small also  research  for  to  is  to  under,  selection.  In  in  to  small  physical  natural for  rivers  sand  intermediate  represent strategy.  also  intensity  the  of  a  deserve  prevails  Considering  is  controlled  transport  aspect  rivers),  current  low  thesis  interest  practical  of  bedded  in  rivers.  material  seems  which  work  • first  full-scale  the  is  system  the  similarity  exercise  of  of  of  under  the  gravel-bed  coarse for  of  this  working  phenomenon  and  thesis.  verification  which  be  rivers  concept  this  the  can  of  the  Hence  a  such  limitations  of  The  to  with  of  arguments,  phenomenon  state  conditions.  intermediate  finer  This  out  modelling  through  practical  under  turns  range  above  possibility  rivers.  The  by  formative  the  the  the  a  "generic"  compatible  situation.  the  geomorphological  attention.  rivers  with  to  a  research  physical  discussed  of  with  for  field,  the  particular  of  exercise  hence  of  a  proposal  and  general  further  concerned  observations  hypothesis on  modelling  the  perspective  hence  the  more  the  geomorphological  applicable  a is  the  research  be  to  is  If  in  principal focuses  for  for  to  consequently  In  which  observed  considered  the  comparison,  modelling  of  allowed.  of  research,  processes  generalization  is  extension  field-laboratory  be  field,  a  and . size,  practical  An  immense  conditions  is  manipulate  the  with  that  regard  of  of  which  to  of  a  of  operation.  which  bring  chapter  most  intensity  a  pool-riffle  subject  of  the  work  are  for  need  the flows to  be  hydrograph  the  theory  to  timescale  highest  sediment  the  will in  demonstrates  timescale  of  similarity,  under  controlled,  fully  formation  and  this  field  This  of  3),  chapter  4).  the  of  the  described  river a  material,  pool-riffle the  of  in  flow  low  transport  sequence.  8ecause  pool-riffle  current  sequence  research.  As  configuration brief  in  statement  contained  understanding  the  in  regarding sequence processes  which on  an  morphology well  which  the  appendix,  the as  the  as  the  entail  its  maintenance.  project,  hydrodynamic  pool-riffle  chapter  the  limited  knowledge  for  performed,  order.  sedimentology of  is  feature  pool-riffle  rivers,  vehicle  be  our  the  such  sequence  is  of  in  natural  measurements  In  the  to  response  the  contracts  characteristic  consists  ubiquity  represents  lack  of  further  support  its  addition,  only  and  conditions,  fundamental  rivers  its  and  In  simplification  of  freedom  Also  the  theoretical  the  characterize  rivers,  amount  principles  experimental  to  experimental  2.  The  of  The  has  reduced.  significant in  under  parameters.  intensity  situation  the  small-scale  controlling  results  particular  thereby  considerably  a  This  working  experimentalist  transport  transport  of  and  the is  low  modeled.  the  system  observation  case  a  advantage  and The  in  situation, a  measurements Blaney  corresponding  comparison  of  were  creek  physical  hydrodynamic  model  performed (described (described  measurements  in in in from  the  laboratory  current Both  and  research chapters  observed  field  exercises,  hypothesis, also  processes  feature and  their  condition.  /  is  that  also  some  is  the  presented  extended  implications  test in  discussion regarding  of  chapter about the  the 4. the creek  8  2.0  Scale  2.1  models  of  chapter  hydrodynamic determine  presents  modelling  the  models  are  range a  entirely  were  largely  based  studies  have  application  century  complexity  difficulties still  to  fluvial  of  or  study  study  the  case  model  or  a  information  inherent  to  the  phenomenon  of  well of  movable be  physical be  flow,  were model  scope  of  analysis  in  the  twentieth  for  Scale  of  the  models  are  useful  adjustments for  laws  the  and the  the  phenomena  models  However,  of  with  transport  and  certain  characteristics respected.  in  combined  engineering  model.  valid,  and scale  of  processes.  channel  these  1915).  sediment  in  "art"  dimensional beginning  almost  ago,  widened  mathematical  as  bed  were  century  conditions  and  channel  as  must  the  boundary  use of  to  of  Buckingham,  flow  prediction  of  at  the  the  geomorphology  the  ;  formulate  constrain  prediction  1915  physical  However,  and  introduction  mechanics  undistorted practice.  a  experience.  for which  intransmissible  bases  support  criteria  techniques  an  theoretical  fluid  research  About  modeler's  the  (Rayleigh,  The  as  which  for  modelling  the  empirical the  for  engineering.  gained  of  situations  considered on  and  introduces  alternative  in  since  field  of  scale  developed  techniques  theoretical and  useful  Historically,  flow  rivers  Generalities  This  the  alluvial  open  in for in  physical limitations channel  2.2  Similitude  Similitude  is  an  important  mechanics.  Similitude  concentrate  primarily  on  The  concept  scaling  laws.  engineering  are  analysis  made  and  the  in  and  in  contemporary  associated  development  of  clear  concept  the  similitude  of  rationale  fluid theory  hydrodynamic for  following  scale  model  models  in  quotation.  " A model of some physical system (the prototype) may be thought of as another physical system, normally but not necessarily, of smaller size, which reproduces the physical phenomenon in such a way that measurements made in the model can be used , by the application of correct scaling factors, to predict accurately the phenomena to be expected in the prototype. " (Sharp, 1981, p.29)  Accordingly, accurately said  to  two  physical  reproduce  the  be  consist  The  of  complete A  similar  systems  equations  parameters.  the  distinction  can  of  phenomenon  different  phenomena  a are  can  which  of  independent of also  size  each  system.  described  quantities physical  which  other  are  between  The  actual  and  of  which  are  a  set  a  physical  are  required  the  system for  (Yalin,  parameters  variables composed  of  characteristic  phenomenon  made  dimensionless  by  their  parameters  the be  be  interrelate  characteristic  definition  variables  physical  of  "similar".  Physically analytical  systems  of of  a  1971a). and  a  the  physical  characteristic  parameters. Since channel  three  physics  dimensions (i.e.  length,  are time  generally and  used mass),  to there  describe are  open three  conditions the  of  linear  similarity.  proportions  prototype  and  similarity  requires  particular  model  the  However,  Kept  that  the  the  shape  of  preserved.  the  ratios  scale  one  have  is  full  of  call  for  and  CabelKa  restrictive  concept  of  mechanical  recognized  as  similar the  and  if,  paths  similar.  mechanically for  According  always  represents  the  proportionally  case  of  acting  forces  to  develop  basic  pressure of  from  fluid's  hypothetical  from may  the  fluid motion  fictitious, inertia  force.  are  geometrically  also  points,  geometrically  mechanical  similarity  dynamic  similarity. but  latter  that  not  circumstance  forces  to  in  external  force  more  systems  kinematic  another.  adequate  to  a  being  Hence,  ratios variables  fluid  can  system  fluid  related  forces)  are  dimensionless  the  forces  (viscous  of  model.  Forces  (drag  are  The  system  forces),  the  the  homologous  and  requires  laws.  in  definition  are  at  includes  represent  forces  they  definition,  distorted  one  difference  properties  Another,  a  any  similarity  Two  times  similarity.  of  model  as:  if  Kinematic  similarity scaled  characterized  a  at  introduce  masses  similarity  geometric  Mechanical  the  such  the  Kinematic  forces  rigorous  similarity.  proportional  geometric,  dynamic  necessarily  and  to  includes  Meanwhile,  in  shape.  dynamic  more  similar  and  streamlines  (1981)  proportional  described  same  that  preserved.  a  Novak  model  corresponding are  similarity.  requires  the  Finally  system  can  similarity  between  they  that  that  and  are  hence  time  necessitates  Geometric  and  to  be  (gravitational the  physical  forces  resulting  forces). might  Inertia  also  force  be is  considered;  described  as  the being  equal  to  system in  the (i.e.  the  of  resultant of  the  opposite  the  same  forces,  forces  Newton's  be  expressed  Fj  the the  as  law  pl3  =  of  =  particular acting  describes  the  state  since  fluid  it  is  system  inertial  to  analysis.  inertia  not  experiences  force  similitude  mechanics,  a but  thus  the  in  resultant)  hypothetical  of  1980)  acting  the  any  of  i2y2  p  as  is  basis  (Kobus,  forces  force  It  ratio  second  r  This  Because  constitutes  to  the  magnitude  system.  measurable.  inertial  all  direction.  physical  directly  of  acting According  force,  Fj,  can  :  pQ2/l2  (2.1)  1  where  pi  is  3  density  of  system,  V  proportional  the  fluid  is  the  and  velocity  to 1  the  is  of  a the  mass,  p  is  characteristic fluid  and  the  length Q  is  mass of  the  the  fluid  discharge. For  the  three  principal  gravitational weight,  g  forces  =  g  is  may  viscous  F ,  partial in  of  g  analysis,  open a  we  will  channel  fluid  particle  consider  the  systems. is  pl g  given  The by  its'  the  be  T  and  F is  v  from  =  v  u.  gravitational  derived  fluid  (2.2)  3  F /l2  where  this  i.e.:  where v  of  force,  F  F  sake  u.  =  = u-Vl the  the dv/dy  acceleration. equation  of  The shear  viscous stress  force for  a  i.e.:  u.v/1 = u.Q/1 coefficient  (2.3) of  dynamic  viscosity.  Finally  the  resultant  F  drag  = pl v2 C is  Similitude  the  drag  in  a  applies  forces,  = *  <  . '  F  P  j2 2  kinematic  =  fundamental  cannot  analysis Yalin and  is  general  The on  right,  the  namely  completed of  force analysis  does  formulation  of  not the  two  Froude  and  define  can  this  of  scaling  point,  approach. As  require physical  out  more any  which Similitude  pointed a  be  hydrodynamic  hydrodynamic  the  consists  contains  parameters  at  ratios.  of  the  which of  coefficient  (2.7)  dimensionless  treatment  also  (2.7)  expression  limitation  which the  as  relationships  via  )  y  (gl)0.5  two  dimensional  about  V 1  the  the  only  (  latter  inherent  method  represented  y  known  satisfactorily  (1971a),  information  or  scaling  proceeds  is  variable  (2.6)  V  u,/p  an  dimensionally  to:  develop  be  a  thus,  similarity  (2.5)  )  r  Those  represents  v  g  )  However,  and,  i  numbers.  modelling.  of  write  i  quantities  to  follows  form:  yj  viscosity.  Reynolds  F  equivalent  )5g  as  principles  dependent  PQ  v  used  g '  r  is  V  where  can  (  r j  also  forces  the  one  F  the  of  If  nondimensional  * (  expressed  coefficient.  ratios  *  which  be  (2.4)  drag  equation.  Fd or  the  creating  homogeneous by  can  d  analysis  by  F^  2  d  where  theory  forces  by  flexible particular  phenomenon.  This  method  will  2.3  Dimensional  be  considered  analysis  and  analysis  is  in  the  the  following  section.  development  of  scaling  c r i t e r i a  Dimensional a  method  system  which  when  formulated the  it  has  of  (Sharp,  excellent  start  for  to  be  Indeed, requires  parameters  only  that  system  one  well-formulated combinations time,  the  hydraulics (op.cit,). reviewed  a  rules  analysis  The  such  this latter  were century is  well  based  no  on  analytical  represents Since  are  an open  particularly  analysis,  the  determine  of  and,  similarity.  the  best  of  the  at  the  same  methods  the and  and  dimensionless  Two  into  Rayleigh  necessitates  simple  possible  introduced  amongst  parameters  quantities  which  relations analysis  application  perhaps  is  but  similitude  characteristic  by  by  method.  dimensional  mechanical  which  i.e.  physical  analyzed  they  determines  then  a  investigations.  a  The  of  be  interest  with  the  analysis,  provides  complex,  dimensional  for  to  method,  of  system,  will  the  criteria  early  via  1971a).  from  dimensional  system  determines  (Yalin,  The  researcher of  partial  homogeneity,  contrast  the  complex  rather  studied  in  that  too  experimental  are  of  characterization  1981).  physical  mechanics  susceptible  the  dimensional  the  method  in  become  of  explanation  some  used  methods  principle  channel  is  a  field  by  known  of of  Buckingham and  will  be  briefly.  Buckingham  (1915)  presents  the  full  deduction  of  his  method  as  well  as  several  mechanics.  Briefly,  variables  in is  of  physical  consistent  analysis  which  called known  derived  of  of  parameters,  which  dimensions  and  one  describes  at  the  the  that  the  of  functional parameters  number result  dimensionless  his  fluid  number  and  to  (n-m)  of a  the  each  selection  dimensions  the  of  characteristic  and  showed  of  1971).  combined,  interest  form  the  fundamental  field  deductive  m  of  of  a  variables  method  has  ir-theorem).  necessitates  of  the  that  of  (hence,  the  independently  number  n  contain  ir-terms  simplest  Those  shows  number  would  to  nondimensional  Buckingham  as  the  the  phenomenon  involved.  In  method  to  dimensions  become  applications  consistent,  related  he  its  his  a  equation the  of  some  should  time,  The basic  be  which  the  with  order  method  in  should  each  also  to all  interest,  other  the the  can  parameter  create  be  (Yalin,  number  contain  of  to  can  quantities  equal  phenomenon  in  ir-terms  other.  of  phenomenon  method,  be which  dimensionless  v a r i a b l e s . If flow  we  consider  over  a  conditions,  we  parameters  (we  be  irrelevant  (1)  Physical  the  case  granular can  in  ignore the  parameters p  :  u»  :  bed  deduce  will  of  an  low  following  surface  the  incompressible  under  the  present  water water  of  tension  steady  sediment list  of  effects  uniform transport  characteristic which  analysis):  fluid  density coefficient  of  dynamic  viscosity  should  (2)  Parameters  of  V  :  Parameters  where  (4)  the  w  :  d  :  We  the  flow  the  geometry  (  i.e  the  channel  )  occurs  channel  channel  which  width  mean  depth  describe  the  characteristics  of  the  boun-  materials  The  flow  :  general  shall  accounts  a  for  the  and  effects  of  D501 as  the  grain  the  now  Generally,  d  g,  for  distribution, V  characteristic  constant  assume  situation.  size p,  of  gradient  describe  phenomenon  D  (5)  velocity  energy  which  Parameters  dary  flow  mean  :  S  (3)  the  accelaration  that the the is  basic  size  the  due  to  gravity.  characteristic  boundary median  diameter.  material diameter  employed. quantities  The  on of  diameter the the  selection  necessary  for  general grain of the  application  of  dimensional  dimensionless  analysis  = { (9d)  where  v  is  equation Froude  the  and  width  irl  depth  X  numbers  ratio ir5  is a  and  following  one  the x  can  of write,  }  the also  ir4  the for  as  obtained  gradient  which  itself.  list  similarity  the  parameter  prototype/model above  from  of  roughness  by  in  well-known  consist  energy  variable ratio  (2.8)  viscosity,  relative  the  dimensionless for  were  a  simply  parameter  then  which  of  S  represent  ir3  and  stands  x  characteristic variables,  the  Kinematic  ir2  above.  represents  If  of  and  Reynolds  respectively. already  ,  coefficient  analysis  to  w  0.5  (2.7).  similitude  to  expression:  Vd TT i ; i = 1 , 5  leads  of  of  any  dimensionless  requirements:  X 2 U  1 .0  x„x g*d 1 .0  X  X<j  v  =  k  w  =  (2.9)  1.0  1.0  *d  =  and  X d» case  1.0  of  a  X  w  geometrically  are similar,  all  equivalent  undistorted  model  for and  the can  be  substituted fixed  by  on  with  earth  the  irl  same  and  fluid  1  According  at  length is  v  the  =  v  scale,  mechanically  similar  model  appear  impossible  since  scale  (Xy  Therefore, would  not  However,  as  these  are  The model  we  w  = X  is  forces.  given  are  would  for  (Xy  the  considered  predominant  1/X|).  scale  such  relaxation  admissible  with  =  small  under the  smaller  incompatible  similar  later,  a  results  law  realize  of  prototype  law  is  If  water we  over  that  of  similarity  as  a  similarity,  X  discuss  prototype,  overwhelming  geometric  to  criteria  law  the  gravitational  Consider  if  model  conditions. of  one  some  of  limiting  respected.  Froude  and  Xj)  mechanically  shall  scaling  any  scaling  possible  we  two  conditions  is  be  works  redundant  realization  scaling  =  strictly  the  for  Froude  Reynolds'  a  one  (2.10)  conditions,  from  is  g  situation:  latter  those  if  carrying  1  2  X  temperature.  ir  the  velocity  X).  fixed same  other following  X  scale  also  about  the  and  to  X  (all  plus  =  g  unique and  ir2  information)  X  a  flow  accept other basic  is  since,  in  primarily  that  the  forces  and  the  governed  action if  both  we  by  of  gravity  also  include  requirement  for  mechanical  the  scaling  i.e:  d  can  = X  D  = X  further  S  = 1  derive  (2.H) from  TT1  Froude  velocity  scale  Xy By  =  substitution  ( X , into  (2.12)  )°-5 or  manipulation  of  the  latter  scaling  law,  we  can  and  also  obtain  dynamic  variables  where  X-t  force  scale  This  of  series  XQ  =  ( X ,  ) 2 . 5  X  t  =  ( X ,  ) ° - 5  X  F  =  X  X  T  =  0  Note  presented  ,  for  kinematic  instance:  time  scale,  Xp  the  shear  stress  for defines  what  the  have in  system  other  (2.13)  that  could  for  3  the  laws  analysis  X,  p  for  scaling  laws  physical  ratios  X,  Xxo  scaling  scale  the  and  model.  of  of  stands  set  Froudian  a  same  been  section  is  refered  from  this  the scale.  to  dimensionless  obtained 2.2:  for  as  variables the  confirms  a or  similitude  their  physical  s i g n i f i c a n c e .  2.4  Froudian  2.4.1  scaling  Natural  stream  (hydraulic  It  is  Froudian  Froude major  of  Downstream in  fluvial  regime of  at  smaller  hydraulic  information  studies for  in  of  is  the  to  may  be  the  channels scales  "  are  asked.  of  The  to  streams  issue of  model  of natural  natural  appropriateness  is  of using  natural  scale. studies,  well  engineering, the  significance  behaviour  relationships  geometry as  the  question "  scaling  geomorphology,  canals  the  regarding  a  range  what  respect  other?  derived  behaviour  ask  stated,  importance  a  river  results)  with  each  natural  over  to  laws  Otherwise  theoretically river  behaviour  legitimate  models  and  geometry  scaling  channels.  laws  present  as  which  are  conceptually  provide  the  numerous equivalent  basic  considerations.  source Those  empirically form  obtained  of  power  yj where continuity x  an  functions,  = a  y-,  relations  Q  (Q  the  latter  the  unsteady  character  discharge  has  not  (exponent  b)  then  will  the  sufficient  well  be  of  a  most  a  Most  often,  the  terms  demonstrated  on  a  reference  discharge  the  since  the  of  universal  present the  of the  to  in  is  analysis.  width/discharge  depth/discharge  interest,  result  significance  for  the  is  and  discharge.  surrogate  considerations,  as  flow  proportion  formative  flows.  as  the  of  parameter  This  actual  as  as  river  been  of  constant  its  yet  part  to  used  1984).  the  a  natural  although  considered for  is  discharge  been  discharge  Moreover,  a  referred  of  has  (Knighton,  relations  Vwd), is  for  nevertheless  parameter  Qf  necessity  basis  any =  The  morphology  in  (2.14)  represent  "formative"  presented  as:  x  exponent.  river  such  customarily  f  equation  banKfull  are  (exponent third  f)  relation  is  fixed. Downstream  various  papers.  reports 0.32  b  extend 1986).  In  exponents  and  0.47  relations The  hydraulic  with The  an  (except  about  channels  gravel  bed  river  number  <  1.0),  as data,  and  are  0.57  and  f  0.59).  These  proportions  of  width  nine  orders  and of  of  exponents  well  as  some  mostly  for North  Church  American.  between  hydraulic  geometry  explained  variance.  depth  relationship (Ferguson,  considered  irrigation  subcritical  in  (1980)  exponents  magnitude  ranges  all  summarized  manuscript,  channel  over  foregoing  and  of  high  the  discharge  experimental  0.5  one  show  results  unpublished  between  commonly  results  geometry  flow  canal (i.e.  Classical  some and Froude regime  studies  (e.g.  Albertson, values Hey  1960  of and  values  of  wide  range  systems,  between  that,  was  scales, that  a  open also  can  be  for  Froude to  in  0.40.  one  result,  number  Q  0 . 40  g  0.20  similar Clearly  of  f  exponents  However,  for  average a  very  largest  0.55  may  was  light  river be  more  channel,  the for  (2.7),  discharge. to  presented  of  criterion  of  likely mechanical  the  This  in  Froude  form  of  the  set  the  required  the  discharge  and  i.e:  (2.15)  length  channels, this  variety  bear  which  between  the  near  press).  similarity the  Ming  of  these  about  equation  of  and  world's  reformulated  parameters  as  in  In  f  (average  a  b  that  of in  terms  Froude  L  the  the  Church,  channels.  given  of  from  respectively.  Froude  and  (mostly  0.43  f  canals.  Finally,  0.55  and  and  0.50  rivers.  studies  suggested  above,  b  Indian  of  and  and  studies.  exponent  and  the  consider for  b  bed  0.30  including  reconsider  number  equal  0.35  of  of  we  and  analysis  geometrical  If  0.50  now  proportionality the  be  Simons  suggest  exponents  river  consistency  ;  mostly  0.39  worldwide  may  (Kellerhals  similarity  Froude  to  it  of  predominance  Russian  relative  similitude  number  and  for  gravel  exponents  and  us  British  1958  typically  b  f  appears  Let  report  between  about  it  etc.)  exponents  the  appropriate  our  also  according  remarkable  ;  respectively  from  Chinese  environments,  Lacey,  b  and  from  0.33  0.35  ;  1969  (1986)  of  Hence,  be  and  reports  0.36)  1949  Blench,  Thorne  0.48-0.50)  is  j  0.50  exponents (1983)  Ingiis,  does  b  scale, and not  equation f  seem  exponents to  be  (2.15) should the  case  shows both for  alluvial  channels  results  of  hydraulic  situation  2.4.2  a  of  natural  downstream  related  to  controlled. studies  that  from  the  Variation even  kept,  as  natural  Church  discharge  and  to  experimental to  channels  a  length  in (or  grain  tend  to  reaches,  to  well  by  would  diameter  develop  demonstrated  as  a be  geomorphological  basin  Froudian  scale  basins  size  less  constraints  size  many  the  equivalent  the  grain  in  the  which  drainage  is  regarding  produce  drainage  Rood,  data ensure  and  depth  diminishes  its  outlet.  documented in  but  ordinary  proportions the  finer  do  empirical  flow  below).  data  were  controlling  plotted  and  in  length  on  Brush  not results  field rough a  scale)  way  those  and  (bankfull) with  some  Data  were  experimental  situations,  i.e.  section  2.5.1  (ref. that  (extracted  one  (1961).  from  of  such  data  together  conditions  hydraulically selected  channel  graph  representative fully  river  were  Wolman  that  and  (a  bed  1983)  from  subcritical The  gravel  width  were  size  such  above.  Therefore,  grain  scale  a  bedforms  be  plot  median  of  downstream  for  concerns  to  natural  bed  steeper  to  screened  river  roughness  most  been  documented  the  presented  from  in  headwaters  if  has  length  well  the  in  grained,  is  reasons  empirical  plot  above  geometry  appear  It  the  channels  roughness  which  The  geometry  clarify  hydraulic  the  surrogate)  seem  to  aforementioned  consideration.  hydraulic  approach  the  studies.  further  Deconstrained  behaviour  to  geometry  warrant  The  of  according  a  plot  discharge  of  the would  approximately contained  in  equation  relationship  fitted  Figure by  eye  2  width/discharge 0.417.  It  and  conform  to  equation  (2.15).  the  that follow under  due  material  as  In  to  typical models. certain  The  constraint  imposed  factor  on  requirements is  thus  natural  upon  the  proposed  channels  met by  by  for  similarity  not  affecting  nearly  control  It  are  the  prescribed  Froudian  latter  of  channels  the  that  by  and  laws  in  the  do  natural boundary  resistance  to  flow,  the  most  dimension.  context  validation  evidence  between 0.425  similarity  1).  and  interesting.  constraints  Froude  figure  clear  underlying  impact of  In  present  research  results  shown  Froude  scaling  laws  of  fact,  Appropriate  the  the  and  gravel-bed  conditions,  of  of  rivers  experiments.  (see  fitted  depth)  most  alluvial  the  prescribed  the  an  the  of  conditions.  channel  significant  natural  exact  presents  favorable  whence  terms  proportions  systems  the  not 2  the  in  and  the  though  the  0.34.  respectively  Froudian  even  and  relationship  when  as  relationships  are  the  withdrawn,  occurred  data of  (width  are  of  the  the  exercise  that  are  and  of  criterion  exponent  scales  this  requirements  scale  figure  length of  This  was  points  appears  environments  similarity  data  presents an  depth/discharge  therefore  size  the  similarity  1 has  exponents  natural  grain  which  results f  figure  eye  channel  and  Froudian  (2.15):  shows  The  b  the  by  between  discharge. The  follow  their  figure river  2  easily  be  the  range  feasible  subject  of  be of  in some  small  a  only  consists  study in  spans and  can  2  the  processes  studies will  figure  for  prototypes  model which  on  project,  scale between  controlled realized the  if next  Figuro 1. Grain alza voraua dlicharg* plot for tho toloctod tot of data 100  E  0.1  H  0.01 0.0001  0.01  1  100 Bankfull Olaehargo ( ema )  Flgur* 2. Doconatralnod hydraulie goomotry plot 100  10  H  0.1  0.01  H  0.001 0.0001  0.01  1  100 Bankfull Dlicharg* ( ema ).  section,  2.5  are  respected.  Criteria  for  scale 2.5.1  a  reproduction  roughness  The  balance  the  a  the  assumption  The  low is  composite  of  bed  for  flow  uniform  flow,  the  grain  distribution.  these  of  resisting  transport  its  forces For  purpose  of  rivers  the  forces frictional  is  essential which  intensity,  the  a  have  rigid  bed  of  the  analysis  use  of  average  which  are  of of In  channel  rearrange,  for  area  we  get  y  R S  the  by  include  the  any  and  given  the  uniformly of  the  consider  the  cross-section by  shear  well-known  as  we  a  to  shear  stress  uniform  of  hydraulic  diameter  if  1982).  assumption  idealized  terms,  complex,  Bathurst,  geometric  perimeter by  very  representative  general  over  unit  a  a  paper  the  resisted  per  review problem  use  the  represents  the  force  flow  be force  TQ),  and  formulation  1966)  T  R  or  reflects  of  gravitational  where  and  similarity.  a  propulsive  (Henderson,  of  the  (see  latter  and  (represented  characteristics  channel  resistance  distributed,  we  of  problem.  simplifications  size  a  sediment  phenomenon  parameters,  if  representativeness  propelling  mechanical  admissible  Channel  the  preservation  of  resistance  steady  the  frictional  between  context  Common  of  boundary  relatively  flow  of  length  characteristics. in  test  models  The  along  closer  is  0  the  =  hydraulic  (2.16)  radius  and  S  the  energy  slope  of  the  flow  (in  most  practical  cases,  identical  with  the  water  surface  slope). Let the  us  consider  resistance  following  problem  set  channel,  of  i.e.  related  to  these  five  the  which  (where equation  ff  for  the  is  a  gradient theorem,  ir  of  this  a  (2.16)  quantity  S  If  of we  on  the  of  the  the  following  (2.17)  the  significance  of  the  term  on  (2.17).  term,  in  the  form  of  the  left  member  i.e.  p  V  (2.18)  2  coefficient  termed  the  friction  factor),  into  gives  (2.19)  = is  gRS  / V  (2.19)  2  equivalent  in  form  to  the  Darcy-Weisbach  formula  8gRS ff  rough  function  acting  TQ  of the  a  1971a).  R  moment  equation  = ff  0  as  (Yalin,  driving  the  v  of  ff Equation  using  {  (2.17),  T  the  in  mechanical  expressed  stress  Consider  flow  Any  V. be  for  parameters  2  Substitution equation  flow.  analysis  VR  consider side  dimensional  ;  f  pV  of  can  shear  grouping  TO  left  and  process  get,  a  parameters  R  incorporates  can  dimensionless  the  D,  average  we  of  two-dimensional  characteristic  boundary,  us  for  p,  flow  the  Let  results  characteristic  u,  consider  system,  the  8  V»2 (2.20)  = V2~  V2  where as  V*  the  =  shear  dimensionless for  the  (gRS) 0  velocity.  variable, balance  Shear  a  in  estimation  is  appears  needed.  in  theory.  the  Over  expressed  over  propelling  velocity the  boundaries,  for  (  0  (  tc  V -V 2  is  2.3K  velocity  measurements From of  requirements regard  boundary  layer can  be  the  1  Von  Karman  via  constant.  measurement fluid  shear  allows  shear  a  force  profiles  (2.20)  the  general as  2  of at  closer  in  the  represent  Equation the  some  distance  test model the  of  the  and  the  principal  nature, can  the be  preservation frictional  of  Darcy-Weisbach  used  to  mechanical  friction  formulate  the  similarity  with  considerations.  It  . can  S  (2.22)  follows:  9R ff  local  so.  equation for  (y /y )  (2.21)  dimensionless  to  reexpressed  of  do  its  0  internal  Equation  velocity to  1  the  the  bed.  prototype:  log  estimate  of  distributions  factor  also  )  1  as  an  profile the  )  known  provides  spatial  stress  above  profile  as  (2.21)  p  above  never  shear  introduced  --  (2.21)  is  as:  T  where  accounts  measurements  velocity  a  forces.  classical  the  includes  boundary  expression  of  known  which  hydrodynamic  shear  development  is  5  formula  alluvial  local  The  rough  and  an  a  -  0  coefficient,  detailed  thesis,  / p )  0  Darcy-Weisbach  retarding  for  this  ( T  resistance  between  Therefore,  intended  The  distribution  uniform.  =  5  =  constant  be  i.e  it  can  gradient.  decomposed Equation  preservation model.  of  the  must  object In led  factor  to  ff  have friction  of  the  fluid  mechanics the  factor, These  versus such  as  of  3  of  a  flow  the  the Froude  resistance  which  will  that  be  Reynolds  number  Numerous pipe  and  be  (modified  from  situations  relative  various  by  a  1959  the  boundary plot  relative  Rouse,  the  experimental  between  represented  for  friction and  flow  the  problem  the  relationships  number can  resistance  shown  the  the  number  figure  energy for  by  effects  considered  of  Reynolds  Reynolds  the  have  which  relationships  the  of  boundary.  nature  the  ensured  scale  we  roughness  roughness.  values,  (2.17), function  revealed  the  requirements  be  analysis  a  in  be  and  below.  dimensional  equation  must  relative studies  above  the  would  some  discussion  number  that  preservation  consider  the  Froude  forces  the  also  the  informs  resisting  of  the  which  ff  (2.22)  However,  condition  into  of  roughness by  Kobus,  1980). The diagram but  above as  it  analysis  figure  is  possible  hydraulic  radius  of  boundary  the  Southard, the  1984).  resistance  conditions transitional  3  were to  is  the  use  used  The diagram  if is  laminar,  research  context,  situations,  belong  to  the  the  properly' which  resistance experiments  channels equivalent  defined  if  the  roughness  (Middleton  and  can  be  recognized  correspond  to  distinct  turbulent hydraulically  prototype  pipe  open  s  3)  so-called from  for k ,  regions  (figure  turbulent  developed  them  and  four  resulting  first  materials,  i.e. and  and  hydr aulically rough.  conditions,  hydraulically  rough  In like  the  flow  smooth, present  most domain.  on  river It  is  VR Re  = 4  v  Re  f f  0  -  5  =  (2  v Figure  3.  Modified  Resistance from  g S )  0  -  5  diagram  Rouse(1959)  and  Kobus(1980)' ro  CO  essential order  to to  ensure  As  we  satisfied This  preserve  Froude  result  scaling  were  of  forces  reveals  that,  relative the  regime,  to  the  dashed  on  line The  formula  4  ( f f )  be  -  5  is  phenomena small  however to  be scale  forces  for  independent  that,  under It  this  is  condition  3 any of flow  provided  should bed  of  therefore  similarity  the  the  Figure  regime, is  (that  respectively figure  be  provided  material  represented  1959)  k /4R  hydraulically  can  3  size  by  the  be  rough  approximated  and  by  the  respected,  the  :  > 200  condition  preserved.  approximate  flow  mechanical  of  and  for  model.  factor  preserved  same.  respected.  s  limiting  This  on  0  be  reproduction  relevant.  limiting is  (Rouse,  factor  sacrified.  depend  Re  latter  to  the  on  can  Reynolds  seek  scale  signifies  scaling  3  in  the  the  the  a  not  is  between  regions  following  the  length  figure  model  gravitational  rough  approximate  that  limit  transitional  said  are  geometrical and  friction  .  This  are  must  friction  number.  roughness  distribution)  the  the  forces  that  regarding realize  similarity  between  we  hydraulically  value,  obtain  the  to  the  Reynolds  possible  by  under  viscous  that  order  scale  prototype  noted  compromise  in  roughness  flow  also  Consequently,  some  viscous  the  contradiction  We  the  mechanical  and  the  laws.  of  strict  model  predominant.  possibility  If  the  in  similarity.  earlier,  if  the  conditions  mechanical  noted  only  is  these  (2.23)  or  criterion  is  Nevertheless,  since  the  does  not  looked  at  turbulence,  the  Reynolds represent in  such  the as  number a  major  model is  the  do  similarity is  somehow  drawback not case  is  if  strongly for  the  velocity  profile  scale  eddies  Reynolds  larger  is  the  the  smaller eddies  to  Southard,  from  (or  is  larger  the  1984)  (Yalin, model  transfer  the  to of  develop  scales  is  a  the the  from  and  the  proportionally the  much of  large  When  turbulence  not  number  for  prototype,  while  perspective  Reynolds  or  1982).  lengthened  1982)  from  as  a  the  scales)  at  phenomenon  referred  Southard, flows  (Yalin,  turbulence  convenient  2.5.2  increased  cascade  scale  and  secondary  energy to  smaller  is  and  number  turbulent  of  (Middleton  structure  changed.  physical  similarity  This  modelling  (Middleton  and  1984).  Reproduction  of  sediment  entrainment  conditions  and  excess  stress  The  matter  conditions  is  a  limiting  one on  In  the  of  is  concerned  case  stream a  pressure  phenomenon lift  bed.  The  correct  is  determined  not  of  further  frictional approached  qualifies  the  modelling. of  entrainment  of  around  conditions  each  entrainment  necessarily  exact  particle  on  by  combination  the  entrainment  however  conditions  reproduction  any  is  physical  flow  albeit  around  It  reproduction  the  that  which  frame  about  field which  above.  the  sediment  to  perspective which  the  related  presented  conditions  involve  the  the  particle conditions  scaling  stream of  bed, drag  of a and  forces. in  of  as  different  the  must  reproducing  strongly  characteristics from  of  a  his  classic  physical  dimensionless  study,  analysis  variables  of were  Shields the  (1936) sediment  proposed  in  presented transport order  to  the problem. describe  results Two the  sediment  entrainment  conditions  v. k Rp  i.e.  a  particle  Reynolds  number  s  =  (3.24)  v plus  a  variable  propelling  which  force  and  the R  F  expressed  the  weight  a  s  From  to  average  flow a  grain  smooth  turbulent,  states  can  latest  version  on  be  considered  specific  weight  Reynolds  number,  as  (section the  2.5.1),  stream  recognized  the  by  Yalin  and  the  case  These  diagram,  Karahan  of  conditions  successively  rough.  Shields  sediment.  flow  are  fully  of  in  the  bed  or in  presented  laminar,  four  of  flow  which  (1979a)  the  will  be  herein.  situation  and  diagrams  reveal  determines  rough  hence  70  and  limit  the  similar (Yalin,  1971a).  model, for  found  the of  conditions  some  1971a)  in  parameter  (Yalin,  after  are  desired  entrainment  above  geometrically  conditions  are  that  the  criterion  the  submerged  transitional  Hydraulically  number  D  particle  analysis  around  i.e.  S  the  high  the  (2.25)  represents  low  between  particle,  =  s  (8-1) where  of  balance  Shields  equation  (2.25)  uniquely,  manipulation,  the  scaling  field  Recent  Starting  following  the  model.  for  the  in  particle with  for  the  an  of  latter  undistorted,  expression factor  Reynolds  can the  define model;  70 X "  =  1  L  [  jO.67 (  where ratio  ' of  V„'K »/  denotes the  prototype  S  v  )  prototype to  (2.26)  the  values. model.  AL The  is  the  preservation  length of  the  latter  limiting  Froudian  condition  scaling  Tg/Tj  or  laws  ensures  (where  stress  sediment  is  preserved  diagram) mobility  number  reproduction  in  the to  and  important  as  of  sand  and  and  Shields of  the  The  patterns  the  of  latter  as  the  appropriate  consequently  1979b). rivers,  i.e. shear  preservation to  of  number  from  importance  bed  use  critical  The  geometry  the  mobility  found  model.  be  with  the  Karahan,  for  the  is  C  bedform  (Yalin  together  that  entrainment  appears  of  roughness mostly  T  for  criterion  form  issue  discussed  is  by  Yalin  (1982).  2.5.3  Reproduction  of  flow  bed  shear  stress  d i s t r i b u t i o n  corollary  A that  at  and  the  homologous  rarely  of  the  results  The basic  In issue is  principal  the  associated  its  distribution.  of  the  similarity homologous  flowlines the  the  the is  open  times  acting  utmost  of  the  on  the  similar bed  However, to  the  model  it  prototype  studies  importance  is model  geometrically  conforms  eventuality  channels  between  similarity).  model  of  in  are  forces  (dynamical if  if  of  are is in river  generalization  foreseen.  prototype  information  these  and  verified  the  and  the  scaled  respects.  processes,  points  similarity)  appropriately  those  mechanical  prototype  (kinematic  very  of  for  hydrodynamic the  measurements shear To  approximate  comparison are  estimates effect  measurements  a  mechanical  with  consist the  the  velocity  obtained  via  closer  test  similarity  of  model  the  situation:  measurements equation on  (2.21)  possible  provided  by  and and  effects Froudian  methods These  of  scaling,  the  measurements  flow  were  structure  performed  must  for  also  the  be  field  considered.  and  the  model  s i t u a t i o n .  2.6  Generic  model  Both  sections  conditions  or  absolute  size  of  present  impossible  to  bed,  (2.26)  customary  eventuality  small,  it  may  be  by  using  strict  will  produce  additional Southard,  parameters  is the  and  from  smaller change  in  by  can  than  lead  situations cases,  of  it  equation  in  or  water  the  to  is (2.23)  between  a  the  the  (1980)  laboratory  equal viscosity  to  be about from  10  and  provide exercise.  the  success  ripple  if  of  geometrical  studies.  obtained  meet  strategy  the  demonstrated  is river  to  This  the  of  bed  even  viscosity  comparison  eventually  and  requirements.  to  ratio  sand  model  water  and  scaling  model  freedom  Romea  field  similarity  the  could  difference  that  in  limited  method  of  effectively  which  latter  scale  similarity  decrease  Boguchwal  latter  mechanical  water  mechanical  albeit  the  possible  warmer  a  is  the  prototypes.  the  the  of  and  size  it  circumstances  large  in  processes  ratio  ordinary the  absolute  prototype  In  limiting  constrained  fact,  most  rivers.  of  explicit  investigation  for  in  the  In  laboratory  satisfy  models-  and  bed.  research  presented  respectively  However, rather  the  its  scale  because  2.5.2  which  generalization  to  geomorphological  prototype  on  large  impossible and  the  and  and  perform  scientific  fine  2.5.1  criteria  sediments  to  concept  Complete the  2.5  by  taking  to  90  degrees  scaling advantage Celcius.  In is  the  case  possible  while  of  to  consider  preserving  threshold which  of  2.5.1).  the  in  In  laboratory An  of  part  whole,  which  a  is  something limiting thus  be  which a  laboratory  stands By  for  exact  are in  systems.  basic  requirements  that  (1)  the  of  refered and  gross  a  the  to  the  In  is  is  one  individuals  share  respects chapter,  can  not  an  which  model  the  it  be  quantitative  can  used  to  manner.  A  necessitate  conditions,  was  (1966)  in  the  contrast  approached paper.  interested  general  in  principles  therefore to  us  with  models.  Bruun's  properties scaling  and  modelling  He  which  situations  to  seldom  generic  this  boundary  generic  but  procedure  in  model.  channel  would  approach  discussion  of  (section  element  in  in  framework  of  system  of  a  in  exposed  processes  some  an  extension,  were family  physical  a  forces  appropriately  leads  generic  laboratory  geomorphologists  population  a  a  engineering  particular  of  If  common.  concept  the  the  respected  hypothesis  in  normal  at  be  it  sediment  investigations  family  the  that  are  a  of  bed  situations,  apparently  current  family.  of  in  of  of  part  the  rivers,  conditions  scientific  "generic"  reproduction  (1968)  series  conditions  concept  modelling  The  flow  representative  investigate generic  this  a  conditions  of  bed  legitimate.  the  sense,  gravel  size  can  limiting  of  etymological of  a  streams  be  extension  introduction  the  circumstances,  would  scale  rough  For  some  such  medium  fully  natural  when  and  reducing  transport.  act  reproduced  small  as of  the  of  relationships  be  met;  argued  study apply  proposed  "similarity  Hooke  Hooke  which  "similarity  by  a  of  a  to  a  general  process".  of  process" (2)  the  The are model  reproduces  some  and  (3)  the  can  logically  prototype.  "  processes be  of  scale  not  were  stated  generic some  model  criteria  developed  in  concept  validity  confirmed  only  be  the  same  includes  appears  to  be  results  will  community.  the  is  being  modelling  is  to applies  been model  be  in  received a  undertaken verify in  in  the  on  the  if a  not  similarity  which  the  order  to  first under  which  formally  and  particular  above  the  model  recognized  in  that  step  or  that  situation.  a  test  laboratory  geomorphological  tenet not  be  processes  Such  before  the  will  the  the  The of  prototype.  in  provide  recognition  framework  ensure  the  introduced  operations.  demonstrated  whether  However  and  scaling  sceptically  logical  views  mechanical  generic  has  Therefore,  research  background  the  it  process"  addition  relation  necessary  not  effect  (1987)  chapter  in  of  in  characteristics  introduction.  of  for  process.  al  the  this  of  when  model's same  et  for  conditions  similarity  The  in  "similarity  process-magnitude  Hooke's  Schumm  the  limiting  prototype;  study the laboratory systems are systems in their own right, not of prototypes." (Hooke, 1968, p.392)  Hooke's  analytically  the  the  :  described  encompass  of  the  have  beyond  models of  explicitly  can  goes  produced  to  further  statement  requirements do  assumed  Hooke  characteristics  which  In this type of treated as small as scale models  Hooke's use  morphologic  the  fundamental of  generic theoretical  3.0  Field  3.1  Site  selection,  The of  study  nature  criteria  and  of  material  bed  exercise  in  a  0.5  be  well-developed to  bear  cobble  range.  The  latter  material (i.e. by  could  fine  be  sands  laboratory  need  to  British  scaled  A University  the  nearly the in safety  small  stream British  metres  material,  mostly  and  the  Because  from  of  Final  the  Vancouver,  campus as  well  of  the  manageable  as  the  set  would  also  were  the  University its  beer sizes  restriction  reach  the  to  limitations.  criteria of  needed  gravel  size  that  the  stream  with  also  the  to  stream  width)  the  ensure  laboratory  selected  in  in  scaling  the  instrumental to  stream  eventual  and  regarding  number  the  Therefore,  forms  a  of  an  riffle  straight.  site  for  of  in  size  for  8  important  modelling,  of  to  restriction  coarser).  Columbia  seclusion,  bed  and  be  accessibility  5  was  The  flume.  operational  restriction  predetermined  important  and  former  from  project  wide  pool  The  follows  were  coarse  description  selection.  - (about  alluvial  relatively  stream  site  metre  small  and  research  field  its  to  this  for  of  needed  location  of  relative  reasons. in Columbia  the  lower  Reseach  Coast Forest,  Moutains about  50  in  the  Km  east  of  Vancouver,  25  metres  was  found  long  (see  figure  from  a  to  reach  of  was  4)  bedrock'  best  meet  Blaney  creek,  selected.  outcrop  has  an  features.  The  preparation  of  overhanging  vegetation,  mapping,  installation for  of  the  of  Conventional topographical shows  the  will  be  of  the  form,  A  study  the  outcrop  There,  a  coarse  material  feature extension sand  can  the  stump  the  its  bank  recognized  (the  still  roots.  to  the  its  is  the  is  bed  level  complex  in  made  of  downstream  of  reinforced in  bank.  1959)  metres  holds  below  this  constitutes  with not  some  the  overbank  particularly  complexity  overbank  of  fine  well  the  banks,  deposits,  limit  determination.  (numbered river  from  partly  and  topped  (cutbanks, allow  appreciated  logged 3-4  alluvial  level  due  which  left  was  About  locally  bankfull  features on  area  the  map  reach  creek as  a  The  downstream  well  on  creek  produce  the  Immediately  impinges  riverbed  indicators  important  debris.  and  the  points.  the  as  pruning  sampling  to  further  of  undercut  involved  of  the  bank  turns  creek,  be  controls  organic flow  elements  can  right  and  The  vegetation)  be  log  between  of  few  These  The  tree  left  but  conf igurational  main  the  along  Six  200  by  large  defined  of  about  vertical  deposits.  a  5)  from  nearly  measurements.  (figure  reach.  the  velocity  is  pool-riffle  across  used  below.  reinforced  cables  were  transverse  generally  and  facilitating  m,  material  methods  principal  6.  bed  lake  downstream  7  site  A  Blaney  alluvial  field  reference  of  of  survey  map  described  figure  and  the  requirements.  located  width  well-developed  bridges  purpose  reach,  average  and  above  upstream  The  straight  of  bears  the  bed  from (refer  1 to  to  6  on  figures  5  figure  5)  and  6).  Contour  (  Bankfull Large Bank  channel  organic  bed  Bedrock units  in  cm  )  limit  debris  undermining  Surface  Bed  elevation  limit  material  grid  samples  Figure  6.  Views  of  Blaney  CreeK  field  site  (a) L o o k i n g u p s t r e a m , f r o m t h e t r a n s v e r s e log. In t h e foreground, r i f f l e and d i s t a l pool. Note the character o f t h e o v e r h a n g i n g r i g h t banK . T r i p o d on b e d r o c K outcrop in the b a c k g r o u n d indicates from where the next photograph was shot.  (b) L o o k i n g d o w n s t r e a m , f r o m t h e b e d r o c k o u t c r o p . In t h e f o r e g r o u n d , p r o x i m a 1 pool ( n o t e c o a r s e bed m a t e r i a l ), cross-over area and f i n e r sediment accumulation bar. I n t h e b a c k g r o u n d , man s t a n d s o n t r a n s v e r s e log which is the d o w n s t r e a m l i m i t o f the mapped reach  41  At  the  upstream  bedrock  outcrop  water  at  At  limit  low  high  flow  most side  gravelly  of  of  Immediately  below  the  pool  proximal  be  related  upstream  to  or  is  the  map)  and  downstream  coarse  which  Opposite accumulation  just  second  (or bar  that  of  is  distal) and  of  and  metres  the pool  of has  long.  riffle riffle  most  extension  nature 15  the  which  the  proximal  area at  the  (6)  and  the  on  flow  distal  crest pool  distal  flow  and  the  is  to of  up  on  left  side  accumulation  of  produces map a  of  the  (3). small  to  material  clearly  a  bedrock  over  The  a  either  show  crosses  stages.  finer  the of than  pool. pool  The pool  is  bank  edge  is  thread  debris  right  area  origin  topographic  the  the  herein.  proximal  the the  low  and  distal  organic  near  where  On  side.  creek,  bed  an  further  the  which  .  pool  on  cross-over  well-defined  end  vegetated  main  of  upper  left  its  pool  (some  some  developed  interest  The  towards  The  the of  side. water  which  side  the  by  by  via  :  of left  left.  map)  developed  relief  All  topped  has  with  m  lower  its  left  proximal  i  covered  on  downstream  pool  its  flow  the  discernable  adjacent (5)  to  on  the  has  (4)  above  Finally,  the  easily proximal  the  features  of  on  the  boulders  its  reinforced  bar  outcrop,  at  on  a  creek.  actually  The  large  end  the  this  by  especially  material  mound  oriented.  covered  is  2)  stump  the  flows  water  -  (1)  entirely  still  outcrop,  the  flow  bedrock  the  to  is  shown  pool  reach,  discharged  outcrop  (not  most  (the  water  the  encourages  is  outcrop  the  deposits  study  transverse  stage the  of  the  found  stages  although right  is  of  represent  riffle shoaling slipface  located  along  which is  the  two  constitutes of  which and  diagonal are  about  subparallel  42  to  the  which  right is  bank  fixed  gradually  by  the  were  taken  over  3.2  Bed  material  To within  the  bed  material surface  grid)  procedures grid within  programme  at  1 of  After  this  included 1  m  of was  X  area  was largest  volumetric been  to  and (bulk)  cleared.  excavation. be  riffle  sample the  noted  grid  the  The  oxidized  the  The  was  next painted  sample  and  later  sample was bedding  subsurface albeit  not  bed  areal  and  following  the  the  surface  distal  would  pool  ascertain  complete could  to  and  sample,  this  in  the  sample  downstream  which  No  used  completed areal  complete  by  sampling  be  considered  conditions.  was  site  the  Moreover  and  if  features sample  layer,  (1987).  location  site's  A  samples  samples  stone  sample  al  latter  to  location,  riffle  downstream the  m  that  et  bed  riffle.  surface  at  on  surface  1  end  measurements  the  necessary  downstream  Church  reach.  of  in  the  in  the  representative  flow  of  was  volumetric,  taken  study grid  it  performed  were  comparing  surface  (i.e.  stability  reach,  next  described  the  A  the  was  samples  the  study  sampling  The  downstream  features.  disrupting  on  log.  its  sampling  selected  material  towards  transverse  these  avoid  widens  of  the  the  collected. the  material, decayed.  study saved  within  surface excavated.  after  change  the  Afterwards  accordingly taken  stones  stones  material  determines  25  the was  the  granite,  the  reach. to  be  the  1  the  depth  Finally, layer  was  laboratory,  X  depth  layer  encountered  mostly In  surface  on  a had  during noted samples  were  oven-dried To  enable  dimensionally adjusted  Bray  (1971).  analysis  the  with  respect  one  considers  the  X  any within well  as  The  comparison  the  that pool  almost from  that  of  median  range.  riffle than This  the  subsurface  The  site  both validates  downstream material.  consideration area  spatial  as  Therefore,  on  near  the  distribution size  than  distribution  material  samples  of as  of  the  study  reach.  within  the  study  reach  in  general  both  size  of study  of  grid  reach  the  is in  not the  decided  the  much cobble sample  study to  are  sample  volumetric of  than  distribution  the  especially  was  detected  taken  size  representative it  be  coarser  samples,  the  No  downstream  the  (in  5.  the  of  four  figure  distribution  previous  and  taken.  sample  slightly  of  if  were  surface  diameter  downstream  evident layer  and  could  distributions  size  surface  each  finer  bed  is  the  clasts  on  compares  size  riffle  surface  25  additional  8  material  that  of  clearly  riffle  the  identical. the  a  downstream  especially  riffle)  characteristics  riffle  the  riffle  but  different  from  of  and  the  indicated  Figure  pool  (on  one  sieve  distributions.  samples  are  showed  sample.  reach  reveal  grid  However,  area  other  five  and  the  at  is  The  similar  Kellerhals of  material  are  distribution  by  the  materal  which  size  results  from  sample.  distribution  feature.  cross-over  m  stations  size  the  coarse  grid  reach, 1  sample  samples in  procedures.  samples  proposed  presents  show  study  other  method  subsurface  the  sampling  either  the  conventional  areal  the  deficiency  1  in  the  7  samples  pool)  trend  with  sediment  to  volumetric  The  comparison  following  The  In  using  Figure  of  location.  sieved  equivalent,  was  distal  and  use  reach the  44  Figure 7. Size distribution! of bod material samples at downstroam rlfflo slto, Blanoy Crook  Slovo slzo (in phi)  Figure 8. Comparison of pooled slzo distribution* for grid ssmpios from downstroam riffle and within reach pool and riffle sites, Blsney Creek  -9.0  -7.0  -8.0  -3.0 Sieve size (In phi)  downstream grid  bulk  sample  . samples  size  for  distribution  and  the  within  scale  modelling  parameters  for  reach  pool  considerations. these  samples  and  riffle  Some  grain  are  given  in  that  all  t a b l e 1. The  nomographs  samples (i.e.  were  the  of  sample  modelling  of  about et  4  1987),  in  a  fact  not  Measurement shear  In three  in  which many  the  128  weight judged  field  the  context  clast  (about  was  arrangements,  of  mm)  be  measurement  of  the  of  scale  the  size  represented  (according to  sample  to  Church  reasonable  programmes)  (it albeit  order  to  across  the  on  the  landed along  the  moved  left  around  piece  of  set  perform 60  top  on wood  of  cm  creek  bank.  intermediate A  instruments  and  estimation  of  stress  transverse  laid  at  situation  in  largest  sample  of  V.  ideal.  3.3  a  total  0.1  characterization  representativeness  issue  The  suggest  confident  The  sample  the  common  for  important  bulk  (1987)  represent  material.  of  al  small  material.  an  the  percent  al,  is  bed  et  should  bed is  of  too  stone  the  volumetric  distribution  Church  actually  largest  weight)  of  the  wide,  at  the  A  7  about  of  three  locations  and  reference  bank  and  wide,  bridges  and  onto  bank  levelled  to  were  They  were  cross-over cables  7  on m  one  allow  flows,  bridges  mounted  cm  the  high  intervals.  40  right in  at  aluminum  metre  bridge  the  safely  long  six  fixed  on  m  right  fourth  debris  nine  measurements  pillars  long landing  was on  measurements  area. was  installed  at  46  Table Grain  1  size distribution percentile diameters ( in s e l e c t e d bed m a t e r i a l samples, Blaney creek  S a m p 1e (  Per cent  Grid downstrearn  site  )  Vo1umetr i c ( Bulk )  mm )  for  Gr i d ( study reach ) Pool Riffle  i1es  D1 6  26.9  3.1  15.4  21.0  D35  4 1.6  11.3  30. 7  34 . 8  D50  51 . 3  25. 1  47.8  49 . 9  D65  61.8  43. 4  59. 7  65. 8  D84  99 . 0  91.8  83. 9  119.4  D90  112.2  97.7  97. 7  148. 1  about  2.5  m  network, for  above  water  each  could  the reach  to  The  mm  and  one  with  (C1  50 a  it  minimum  distance  would  and  the  wake  while  the  slope  during  intalled  level  in  the  during  m  long,  was a rest  of  above to  two  via  the  to  10.5  of  protruding  cm  effects  axis  thus  about  O90 to  particles.  from  and  avoid The  set  to  mutual Benini at  centimeters  next  six on  corresponds  on  the  A the  by  which  values  that  according  six  particles,  The  particles.  was  9).  channels  base  performed  meter's  (see  its  diameter  proximity  4  Scientific  bed  sufficient  of  bank.  at  of  propellor  bed  six  right  plate  m/s  figure  (Campbell  top  meters  2  (see to  appeared  sufficient bed  cables  five  velocity  rod  the  the  and  Dgo/2 be  6  the  first  top  on  on  wall  plate  m  of  maximum  diameter  15  X  propeller  the  -  propellor  meters,  velocity  data-logger  meters  the  surface  of  mm  times  on  the  assumed  20  pitch  six  current  maximum  cm  nearly  between  from  -  installed  small  with  laboratory  counter  Therefore,  was  water  measured  pitch  transmitted  tests  interactions  This  cm  between  laboratory  roughly  C2  diameter/25  3  had  ensured  average  was  in  elevations  elevations  gauge  Ott  which rod  centimeters  map  cable  determined  latter  staff  and  pulse  Instruments)  (1962).  The  the  be  surface  were  were  CR5  boundary  could  water  profiles  mm  to  signals  supporting  From  the  changes  diameter/10  clamped  a  station.  A  bed.  elevations  estimate  the  velocity  30  on  the  periods.  with  Analog  bed  programme.  current-meters  m/s)  on  topographical  to  monitor  measurement  and  with  useful  measurement  point  sampling  compared  were  lowest  surface  velocity  be  former  the  table  meter two  being  2). in  meters'  48  Ott  laboratory  Figure 9. c u r r e n t meter  rod-mounted  array  axes  were  fixed  set  at  distance  ensure  either  was  out  Velocity  of  the  and  flow,  surface  meter  bridges  with  meters  were  the  within  direction  (A.S.M.E.,  neighbouring  1967).  fluctuation mean  depth  local  flow  give  was  the  was  coverage  of  the  structure  bottom  that  to  the  align  flag  when  mean the  was  be  from  the  flowline six  actuality  readings  in  near  foregoing  used  the  and  the The  However  to  on  measured  In  meters  partly  degrees.  from  near-bed  the  judged  they  current  are axial  fastest  everywhere from  Ott  propellor  deepest,  not  water  cm.  2-5  accurate  had  to  direction.  degrees  alignment  current  pulsations  (Jepson,  the  6  observe  believed  within  the  visible  that  of  stations.  Propeilor velocity  attached  was  by  The  upper  complete  to  orientation  It  1971).  a  order  were Their  15  flows,  near-bed  flags  below  determined  obtain  In  depth.  three  separated  shear.  approximately  water  the  The also  internal  diameters  were  plate. would  were  of  or  to  pool.  will  oriented  and  also  accurate  through  23  water  compass.  meters  November  but  local  two  some  the  meters  remaining  stations  clamps.  with  current  cm  a  measurements information  the  distal  50  of  about  flows,  of  grounds  riffle  current  the  set  sampling  morphological the  usually  from  meters  through  shallowest be  respectively  other  spaced  In  cm  near-bed  three  meter  surface.  18  determination  the  logarithmically upper  and  between  accurate  Finally,  could  12  or  velocity,  and  However, turbulence Ott  meters  meter  generally  underestimate if  the  error  transverse  average  intensity  is is  overestimate  less less  components  amplitude than than  of  0.2 1  axial  V.  velocity times  the  (Kulin  and  Compton,  1975).  roughness  flows  such  suggest  values  average  velocity  lowest  intensity 0.3  to  thumb,  Ott  Blaney  Creek  in  drastical  relatively  to  7  m  consider procedures  at  hypothesized  the flow  would  be  least  longer in  creek.  with 5  bear  time  was  the  end  in  This  concern  was  the  rule  bed,  of under  but  not  that  axial  or  a  manipulations  was  measurement  restricted in  spatial the  could  creek  it  to' and  These  Blaney  regime,  out  unreasonable difficult  measurement. since  minute  representative  was  the  was  one  not  it  to  velocity  borne  that  obtain  case,  flood  more  measurements  appeared  and  for a  (1975)  assumed  to  each  flashy  intervals  average  considered  assumed  due  minutes a  turbulence  were  profile  any  intervals  the  insignificant.  which In  measured  conditions  was  sufficient  creek.  time  to  It  figure,  fluctuations  near  V.  the  of  Compton's  velocity  situation  associated  consume  resulted  of  minute.  longer  it  relatively  one  wide  1  for  approximately  velocity  latter  and  a  to  the  latter  values  would  1979)  being 2.0  below),  and  exceed  The  interval  profiles,  a  could  were  be  Kulin  (V  the  factor  relative  Church,  of  Using  creek  due  fashion.  interval  velocity  that  errors  conditions  time  selected  to  and  order  depth.  the  high  V'/V*  description  of  for  (Nowell  the  friction  According  effects  The  for  bed  meter  in  and  conservative  lateral  time  3  the V.  Creek intensity  water mean  table  0.35  a  the and  near  Blaney  turbulence  of  (see  measurements  fluctuations)  (2.21)  events  as  of  third  equation  Experimental  was  reasoned would  have  coverage subsequent  of high  measurements. Due  to  some  technical  difficulties,  most  often  4  current  meters  were  during  actually  field  important flow  in  velocity  working  measurements.  near-bed  meters  and  orientation  speed  explore  the  Velocity  profile stress  site.  For  data  hydraulically appropriate.  In of  flow  in  2.21)  was  of  the  law  fluid  shear  be  and  at  The  used  to  distal to  of  study  wall  for  to  be  provides  an  assumed  some  bed  the  the  wall  pool.  allow  across  law  most  times.  can  locations  times  two  all  order  logarithmic  the  internal  at  riffle  several  (equation  actuality, the  the  the  various the  gained  collected  purposes  rough  operational  of  for  at  Fortunately  information  were  estimations these  estimation  were  hydrodynamics  shear  condition  distance  above  evidence  that  t h e bed. There the  is  law  applies  conditions, water be  depth. kinked in  However,  the  well  on  as  1979)  at  limited  the  law  of  of  estimate  at  bed points,  which  average  Unfortunately,  wall due  X  the of on  flow.  in  not  height  whole  the  Church,  our  profiles  area  near appeared  because  above  as  and  logarithmic  be  is only.  roughness  of  this  to  wall  depth  (Nowell  However,  relative  of  was  (2.21)  could  profiles  Most  distribution  it  velocity  relative  of  shear.  the  water  the  laboratory  through  the  spacing  the  and  law  element  equation  of  the  that  velocity  use  observed  depends  boundary  the  number  have  roughness  field  approximately  15-20  issue  solid  to  determined  lowest  the  The  only  proposed  latter  that  bed.  justified  the  experimental  controlled  authors  have  the  suggested  often  Some  and  abundant  under  albeit  applicable  the  relatively  of  the  satisfactorily the  bed  the  fails. to  some  uncertainties  about  the  exact  location  of  surface) near  the  bed  bed  level,  shear  displacement parameter but  significance  some  had  height  controlled  conditions  appear  above  concerns  with  to  will  Those  to  bed  will  acting  per  which  be  from  area  hydrological  approximately November  23,  on  staff  Although  consistency  height  Bayazit,  1982),  at  the  under the site  to  the  current  to  the  estimates transfer taken  comparable  the  study  Due  the  and  shear  of  roughness  of  level,  be  meters form  herein through  relatively to  the  of as the close  the  actual  bed.  will  be  November  half-bankfull during  gauge)  1984).  measurements  events  on  1986  of  flow  Southard,  estimates to  so.  profiles  height  momentum  shear  assumed  unit  occurred  the  local  internal  Results  Two  the  this  displacement  location  consider  the  the  the  bed  of  velocity  generalizations.  exact  idealized  we  fluid.  3.4  an  describing  the  the  allow  physical  conditions  such  not  The  1981;  flow  preclude  about  (2.21),  actually  force  (Jackson,  granular  practice,  do  relative to  a  concept  In  of  the  the  the  to  and  of could  non-linear  points  respect  of  to  respect  equation  on  with  nonunif ormity  would  few  (Middleton  report  data  1981).  formulation  well-known  case  using  linearizing  too  the  profile  estimation  by  displacement  marked  velocity  hence  authors  (in  (Jackson,  found  and  idealized  our  stress  profiles  not  or  height is  our  are  actual  was  considered.  20,  conditions. which  the  reached  1986 A  bankfull will  be  The  first  corresponds second level of  event (about  most  63  one to on cm  interest.  Twenty-one shows  stations  the  variation  measurement, November  measurements  period  by  and  contrast, during  A  groups.  As  bankfull  obtained November  23  estimated  chapter. reliable  Detailed considering velocity through Let  e  k  bankfull  stage)  and  hydrodynamic the  shape  profiles the us  as  studied first  well  local as  both  (except  and  pairs  measurements  and  from  separate near  provided  the  (stations  a  and the  the  creek  on will  slope)  were  to  data  next from  November  November now  being  the  estimated on  on  particularly  in  temporal  H  23  be  developed be  are  discharge  will  could  events  D  November  along 18  and  flow,  but  method.  slope  pairs  the  20),  considerations  elevation  two  November  stage  surface  of  estimate  velocity-area  peak  reach.  values  on  of  In  data  in  number  parameters  to  water  bankfull  the  cross-sectional  the the  considered  in  gradually  compared.  at  unsteadiness  limited  These  modelling  water  near  2.  near  The  the  of  taken  water  measurement  be  Consequently, be  the  the  thus  of  stations.  stage  during  10  period  after  The  were  will  of  were  the  to  U  hydraulic  and  for  to  the  hours  may  Figure  sampling  few  flood.  coverage  one  by  correspond useful  L  table  from  a  stage.  a  consequence  average in  taken  measurements of  events.  velocity  profiles  and  spatial  summarized  for  measured  measurements  The  during  centimeters  23  K  a  reasonable  (at  the  to  stage  two  recession  stations  water  bankfull  November the  both  were  about  all  during  labels  approached  diminished  sampled  in  with  20  stage  were  5 23  20. be  examined  variability  shear  and  flow  indicates  the  shape  of  by the  patterns  reach. consider  what  of  the  54  Figure 10. Temporal change* In watar laval Nevambar 20 and 23, 1886 event*  •  40  '  i  80  i  i  120  i  i  160  I  1  200  1  r—  240  Time, In minute*  Table Mean 23,  h y d r a u l i c p a r a m e t e r s of November 1986 h y d r o l o g i c a l events, Blaney  November  Discharge ( m s  2  20  20 and creek  November  2 . 62  5. 00  Mean velocity ( m s" )  1.11  1 . 30  Mean d e p t h ( m )  0 . 34  0. 55  Mean w a t e r surface slope  0.0095  0.0102  Hydraulie ( m )  0.31  0. 475  0.61  0. 56  3  _  )  1  1  Froude  radius  number  Reynolds number Fr i c t i on  240  factor  000  0.19  470  000  0.225  23  velocity  profiles  processes. right 23  Apart  bank  the  bear  were  kinked.  materials could  on  variable  local  than  Church  of  can  velocity  be  shown  profile Figures  dimensionless  velocity  1  stage)  (at  high  general,  these  gradients  in  can  the  the  the  November layer  was  determined  by  Above  an  it,  characteristics  channel  of  which  configuration.  Being  wake  layer  characteristics  were  outer  layer,  as  Nowell  for  more  similar  though  found  20  through  by  layer,  reduced.  In to  in  more and  especially actuality allow  was  the  and  over some  the  stations  satisfactory  riffle  that  the  internal  over  still  appeared  is even  kinked.  were  comprise  the  flow  over  the  riffle  profiles  wake  shear  appear  as  velocity  the  riffle  herein) to  area. internal  of  the  shown  riffle,  the  In  velocity  situations  location  often  recession).  than  depth  pool-group  highest  of  (not  the  (during  majority  latter  profiles  show  over  whole  the  respectively  measured  greater  of  shear  the  contrast,  the  pool  2  slope  internal  riffle,  that  a  in  velocity  13 the  were  the  the  pool-group  layer  at  the  for  layer  profiles:  that  to  indicate  that  profiles  (2.21)  and  the  throughout  November regular  and  outer  pool  the  12  profiles  wake  the  equation  11,  note  through  shallow  to  wake  mostly  the  proportional  figures  also  layer  from  is  intensity.  wake  a  arrangement.  the  the  of  bed,  physical  close  most  are  of  (1979).  It  shear  which  terms  located  the  their  factors  those  to  of  by  in  forms,  recognized,  determined  dependent  complex  and  be  area  stations  Close  boundary layer  study  few  more  characteristics  rather  One  a  the  outer are  the  from  which  profiles  found,  through  more only  a  depth  was  were  too  measurements.  Figure 11. Dimensionless velocity profiles Riffle area, Novambar 2 3 , U 8 8  1.1  1.3  Point / Height averaged velocity  * Height averaged velocity w i t approximated by the velocity at 0.2 and 0.8 the water depth  1.8  •  58  Figure 12. Dlmenelonleea velocity profile* Pool area, Novombor 23 198*  0.01-| 0.1  1  1 0.3  1  1  1  0.8  1  1  0.7  1  1  0.8  1  1  1.1  1  1  1.3  11.8  Point / Height avoragod velocity  Figure 13. Dlmenalonleaa velocity prof Ilea Pool areaOower atage),November 23 1888  i  1 0.7  1  1  1  r  0.8 1.1 1.3 1.8 Point / Height averaged velocity  During  the  (Rood,  1980)  In  November of  general,  (except  characteristic seen  from  us  simple  the  of  high  now  two  L  approximately  (pool  about  the to  further  qualify  interpreted. divergence  in  the  attributable  to  the  a  log  hanging  near-surface  (see local  substantially different. profiles  Internal differed  consistency  in  although  the  Internal  shear  bank)  at  on  wake  of  outer  layer  proximity  shape  can  be  variability  of  5  the  flow but  most outer  layer were  in  this  may  gradient  markedly case  P  be  a  clear  might particular distort  by  be of the were  somewhat of  the  showed  some  between  different  differed  might  bottom  Station  X.  are and  was  the  two  shear  gradients  intensity  20  profiles  in  layer  of  considerations  This  which  from  These  shows  and  crest),  distance  estimates  banks  Wake  by  riffle  internal  14).  6)  estimates  measurement.  These  profile  their  the  collected.  the  (figure  field.  determine  velocity  of  or  some  (near  18.  the  event,  a  were  one  of  figure  layers  P  hydrodynamic L,  estimates  as  23  at  figure  station  the  but  shedding  profile  and  station  variation  the  pool.  complex  local  to  profiles  the  shear  the  velocity  right  these  similar  jetting  distal  streams,  order  local  spatial  For  wake  November  in  one  how  the were  the  of  the  divergence  the  pool  bear  issue  done  located  local  relevant  the  from  be  the  of  13.  near  cm  noted  into  roughness  one-minute  10  can  bank)  was  riffle  in  During  were  additional  stations  and  profiles.  stations  the  relative  of  evidence  profiles  address  tests  no  from  right  12  representativeness At  flow  to  velocity  event,  velocity  figures  Let the  the  the  close  23  profiles  (figure up  to  15). 3.6  60  Flgura 14. Local variability In velocity proflloa Station L, November 23, 1986  >  0.2 -  0.01 Maan point valoclty, in m/a Flguro 18. Local variability In valoclty profllaa Station P, Novombor 23, 1986 0.8  o.s  0.2  -  0.1 0.08 0.08  -  0.02  -  0.01  i  1 0.2  1  1 0.4  1  1 0.6  1  1 0.8  1  1 1  1  1 1.2  1  1 1 1 1 1 1 r 1.4 1.6 1.8 2 Moan point velocity, in m/a  -  times, the  which riffle  is  considerable.  crest,  variable  area  which  in  unfortunately  Station  may  terms  impossible  is  correspond  of  to  P  to  velocity  study  also  located  a  most  spatially  distribution.  this  issue  near  It  further  was  in  the  field. Some period  simple  on  the  investigate  water  the  the in  part  intense  description complex  below).  protusion  of  the  to  behaviour  riffle can  station the  temporal further for  one  be  shows  be  are  to  consistent  Therefore,  variation discourage particular  in  the  strong station.  and  latter  over  (see  further  indeed  rather  be  were  attributable to  the  any  case,  for  this  from  average for  least  to  intense the  for of  the  generalization  which  pool pool  velocity from  in  location  is  a  consideration,  layer  (figure  wake for  and  variability  W  profiles  some  local  Outer  Station  the  the mixing  pool  boundary.  consistent.  This  the  located  bank  as  form  former  W  right  than  at  and  the  the  The  V  while  located  profiles  recognized.  more  bed.  kinked  taken  was  profiles  more  the  temporal  profile  In  near  were  to  V  may  effects.  a  Station  profiles  well  order  23  Station  along  as  average  seen  pool  velocity  especially  is  the  layers  near  bank  one-minute  the , distal  in  from  at 18),  this  November  profile  figure  area  and  jetting  constant  riffle.  The  16)  interesting,  on  shearing  (figure  perhaps  the  the  measurements  on  of  of  variability  sucessive  end  end  velocity  of  shown  of  the  a  nearly  (stations  downstream  the  the  nine was  at  of  sources  or  level  distal  made  replicability  Ten  respectively at  were  potential  viewpoint. the  tests  and  17) outer  the  latter  location  even  locations,  the  profiles  may  unique combined  profile with  Figure 16. Sean* at downaiream and of pool Station V, November 23, 1886 100 80 •o  SO  > o  S  20  10 8 8  -  1.3 1.8 Mean point velocity, in m/a Figure 17. Scana at downstream end of riffle Station W.November 23, 1886 100  0.8  0.7  0.9  i  r  1.3 1.8 Mean point velocity, In m/a  1.7  the  local  consider be  variability  before  any  shear  18  flow  pool  (44  2.16),  11  shear  23,  while  25.8  was  important  to  shear  estimates  can  suggest  Pa)  were  well  as  recorded in  the  to  discharge  the  in  average,  (figure  19).  uniform  the  measured  pool,  i.e.  although  flow  highest  the  quite  shear  approximation  shears  was  were  measured  riffle  study  reach.  in  the be  the  to  on (212 was  136  crest  as  the  riffle  and on  bed  unit  smaller  than  28.9  upper  at  similar  each  somewhat  amounts  bed  and  shear  to  within  pool  212  the  on  i.e.  measurements  (335,  Pa  are  which  23  appeared  variable  riffle  the  average  22.2  stage  the in  values  the  shear  estimates  lower  over  the  bankfull  sufficient  At  near  Pa,  near  cover  stations  20  11  in  at  (equation  47.5  November  of  than  be  the  those  shear  formulation  estimates  or  part  Pa)  to  shear  riffle  November  These  shear  internal  (82  measured  highest  upstream the  of  the  the  considered.  not  variability,  over  most  According  pa  that  was  seven  local  are  comparison.  value of  values  of  did  internal  For  flow  average  of  23.  estimated  strict  values  November  riffle  stations  one  the  average  uniform  the  average  for  the  is  a  Despite  to  lower  on  of  average  on  the  these  only  the  Pa.  tend  study  the  estimates,  larger  than  argue  November  replicated,  stress  however,  to  (2.21)  Using  lower  stations:  equation  was  Pa).  the  distribution  comparable  stage  somewhat  again,  of  the  were  to  high  area  via  which  According  the  profiles,  interpretation  shows  estimated  stations  21.8  some  produced. Figure  Pa)  of  Pa.  part  Once of  the  reach. Figures  20  and  21  show  the  flowlines  for  the  November  23  Near-bed  Figure 18. internal shear estimates at Blaney Creek, November  velocity 23, 1986  sampling  Bankfull Bankfull Riffle L  Test  stations  cross-section channel  limits  crest station  9.5 336. 1.6  450-6  0.5  \36.  4.1  •46.5  16.6 73.  25.6 7.2  Note  :  shear  units  are  51-3  P  W  34.6K 16.8 7.4  9-9  V  Pascals  1 m  en  cn  Figure 21. Near-bottom and n e a r - s u r f a c e flowlines, Blaney Creek, November 20, 1986. Note  :  Flowlines are p r o p o r t i o n a l 1 cm r e p r e s e n t s 1 m s ^  to  velocity.  -  ^ Bankfull Riffle  channel  limits  crest  — •  Near-surface  — "  Near-bed  flowlines  flowlines  1 m  cn  (at  high  stage  structure  of  related  the  to  the  impingement flow  only)  pressure  is  the  banks  higher  at  when  November  is  a  pool  riffle  the  upstream  its  downstream  part  be  from  The  could  be  surface  flow  1984).  The  and  warrants  some  21  reveals  that  of  following  in  the  This  well  at  tend  oblique  distal  sediment to  is  pool  to but  event cm). 3  These m  case  higher be  long the  evident. stages.  In  parallel  the  riffle  subparallel  from  of  between  field-flume  in  it  in  may  the  with  axis to  circulation  evacuation the  23  with  to  developed  investigate  November the  every  than  flowlines  of  divergence  in  the  results  40  bridges  is  flow  of was  wide  flows  of  that  with  the  end  gauge  The  aligned  presents  almost  from  more  the  staff  low  the  for  useful  topics  on  and be  at  was  bottom  end.  Problems  (described  at  Surface  consequences  The  pool  (Gallinatti,  22  flowlines  the  face.  to  made  compass.  greater  the  3.5  distal  arising  20  Figure  collected  bottom  distal  the  respectively.  developed  tends  stage level  and  the  in  well  flow  flow  and  will  the  angle  figures  observations  were  flags  some  of  (water  observations  Divergence  events  in  low  discharge.  the  20  surface  a  particularly  surface  structure  plastic  flows  distribution  at  comparison  particularly  event  20  comments.  The  also  if  structure  flow  November  secondary  even  qualitative  and  have  pool.  It  comformation  chapter.  raised  in the  by  this  the  section  appendix)  field  cover plus  measurements  the  reversal  observations  hypothesis on  bedload  cr.  transport during  and  November If  one  makes  23  believes . the  that  than  in  analysis  pool  it  of  the  at  perhaps  that  bankfull velocity  described  in  the  appendix.  the  is  also  apparently  unavoidably  of  of  some  bankfull,  how  the  pool  of the  the  field  latter  On samples  in  some Blaney  November from  conditions,  is  the  riffle  In  the  same  not  meters  over  reversal  bed  the  not  the  current  the appear  hypotheses  topography  obstructions  and  that  measurements  to  through  the  distal  pool  If  Blaney  maintenance.  then  over  in  intensity fill?  raises  occurs  The  sufficiently  creek  at  spatial dense  flow,  near  coverage to  settle  issue.  However, conditions  the  calibre  measurements  the  in  its  transport can  by  would  higher  stress  Although  shear  sediment  These  one  it  lowest were  if  restricted  mention  the  shear  controlled  issue  more  velocities  and  riffle),  to  for  or  lower  the  structure  to  increases.  conditions.  the  values  the  worthwhile  near-bed  to  reach  flow  due  increases  patterns  contrary  the  as  shear  over  discharge  velocity  near  well  limitations  shear  as  is  suggested  riffle  their  internal  the  as  internal  (particularly  the  perspective,  above  of  coverage  appear  conditions  event.  abstraction  spatial  also  transport  using  very  restricted,  least  of  most  transport  medium  other, Creek  on  23,  the a  only lower  76  one gravel seemed  more  mm minute size to  general  November three  occur  are  were  mm) along  were the  the  discussing.  transport  sediment  taken  indicated  about  worth  Helley-Smith  samples (10  23  bedload  bridge opening  considerations  at  bankfull  sampler. that  particles  transported base  Those  of  and the  at that riffle  face.  It  was  could  not  actually  indication bankfull, shear  the  of  stress  is  of  or  calibre.  the  obstruction  model  obstructions,  described  verified  be  examined  that outcrop  lateral  downstream active.  of  the  Lateral  The  characterized dimensionless  Using series single  sorting  shear  Andrews' of  on  but  pool  not  was  to  the  bank  a  basic  could  facts  below  accumulated  November  the  gravel  the  process  such  (1984)  the  immediately  process can  may  further  be' be  23.  stress  (1983)  provide  right  proximal  the  to  flow  streambank  events  the  that  considering  observations  thread,  the  the  the  Nevertheless,  materials  suggest  conditions  by  necessary  in  figure  transport  hydrological  coarse  various to  around  This  of  transport  of  from  may  occur.  near  face  related  field  the goes  Gallinatti's  experiments.  obtruction  from  to  found  very  low  sediment  appendix,  the  flume are  that  appreciated  stress  the  sediments  and  the  during  indicate  pool.  flow  sorting  directly  finer  the in  the  be  in  creek  in  downstream  proximal  of  in  for would  sediment  the  qualitative  for  routes  the  pool,  near  trend  until  either  possibility  of  in  be  would  definitive albeit  apparent  distal  material  no  measured,  much  the  pool,  latter  sorting  mechanism  in  larger  is  the  change  preferential  The  lateral  to  stresses  existence  we  character,  unlikely  if  there  discharge  formative  Lower  determined  Although  the  was  intensity  directly  mobile.  that  overbank.  be  to  entrain  bed  rivers,  of  characteristic  which  various  can  dimensionless  some  results, on  ratio  23  were  size  the  critical  further average  critical bed  developed  particles the  be  shear particles. from  a  transported  in  dimensionless  shear  stress  necessary  materials  for  of  surface  the  shear  Blaney  stress  typical banks  material  (mobility  number  exceedance with  is  exceedance  Simple that  could  mobilize  was  an  bedforms  which  7.  the local  rise  in  would  resistance  Abrahams,  in  over  cause and  the  D/S90/S  than  50  on  A the  the  bed.  overbank  consequently  at  a  1984). criterion, or  the  which  lower  shear  increase  since  would  shear  is  such  a  would  increase  (Hirsch  TQ  an  bankfull  Nevertheless,  flow  rivers  bear  discharge  lesser bed  This  Andrews, as  in  7.  27'/.  bed  2.0)  of  the  by  average  of  a  for  flow.  gravel  data  general.  movement  distributed  flow  from  more  bed  number  0.057,  exceeded  the  5 0  reinforced  bankfull  on  (mobility  using of  uniformly  and  1981).  It  might  therefore  experiences  low  although  creek  the The  is  Perhaps  low  transport  latter  paved  observation not  existence  represents  in  that  decayed  of  proposed  conditions  not  but  continued  be  mobility  oxidized  the  active  estimated  increase  initiate  (1980).  most  100  not  flow  to  compared  D  conditions  been 23  be  with  critical  have  the  dimensionless  to  streams  November  calculations,  reveal  probably  for  the  calculated  the  surface  Using  radius,  bed  would  1.27)  about  (this  gravel  of  D50  0.046.  is  Therefore  pool-riffle of  discharge  of  be  flow  entrainment  low  alluvial  bankfull  1984).  the  hydraulic  small  (Andrews,  surface  would  the  the  for  entrain  creek  and  for  value  to  tends  intensity  that  at the the to  can  near sense  of  Blaney  creek  bankfull  stage,  Bray  Church  subsurface support be  and  material  such  reconciled  the  distal  pool  in  a  relict  feature.  the  assertions. with  eventuality Whether  is  this  the that is  Lateral bed On t h e l e f t bar .  Figure 23. material sorting in p r o x i m a l pool, Blaney Creek. edge of the p h o t o g r a p h b e g i n s the s m a l l accumulation  November 23, gauge is a p p r Yet one can c e x i s t e n c e of  Figure 24. 1986 h y d r o l o g i c a l event, Blaney Creek. Staff o x i m a t e l y a t 4 5 cm ( i . e . 18 c m b e l o w bankfull). learly n o t i c e by t h e w a t e r s u r f a c e a p p e a r a n c e the a shear l i n e along the r i g h t bank.  reasonable We general an  or  not  will  may  also  explore  level.  'eddy'  or  developed  Figure  flow.  A  Outside  the  distance  flow that  the  reinforced the  distal  obstruction  during such  the  as  24  shows  the  November  into  stage,  noted  at  line  is  of  area.  the the as  at  upstream  changing  orientation  described  approaching  flow  cohesive  pool  Its  could  controlled,  right be  above. was bank  similar  event  of  the  This  flow  obliquely and to  that  line  extended  only  bank.  flow  at  some to  streamlines feature  that  the  the  to  the  appears  the  of  receding  right  toward  thus  right  the  begins  extent  that  the  of  a  (1986)  during  feature but  on  Lisle  from  shear  same flows  by  along  the  flow  measurements  distance 23  higher  pool.  we  and  The  the  described  visible  photograph  4.  of  field  some  clearly  the  chapter  characteristics  pool  present  to  in  distal  range  is  some  line  cross-over  structure  discussed  the  shear  the  related  was  shear  in  banK.  near  It  be  be with  suggested relatively origin  proximal,  of i.e.  75  4.0  Laboratory  description,  Flume  4.1  measurement  The  flume  Department  is  with on  downstream  end  0.02.  The  apparatus  width  of  bottom cm pump  diameter driven  end.  Water  through  a  Sediment only  in  grains  recirculated. recirculated The  a  bed  or  a  is  up mesh falls  than  Particles through  to  2  mm  coarser the  had  can than  its  situated inlet  entering  a  2  the mm  a  has  a  bed end the  tilting  15.25  speed  impeller  its'  upstream  at  where  it  flows  flume  bed.  reservoir  return could  about  From  the  downstream enter  to  its  downstream  variable  flume  before  and  figure near  up  through  a  the  jack  pumping.  flows  motor  into  long  tilting  (see  adjusted  at  to  horsepower  transport smaller  pipe  walls  during  water  return  pumped  be  Geography The  levelling  metres  up  the  Columbia.  A  reservoir  the  honeycomb  flume  hydrodynamic  in  acrylic  to  six"  backing  1.0  British  slope  large  reservoir  by  located  truss.  about  A  plastic  is  of  steel  is  cm.  the  study  transparent  allows  drawdown of  this  University  flume  supported  prevents  and  instrumentation  in  the  47  conformation  procedures  used  at  recirculating 25)  and  study  not  pipe  where and  safely  be be  pump. no  installed  device  for  discharge  76  General at The  Figure 25. view of the water r e c i r c u l a t i n g the Department of Geography, U n i v e r s i t y of B r i t i s h Columbia  flume  regulation. method 5  from  to  the  Discharge  7  set  was  set  to  this  approximately  for  each  ensure  discharge  on  a  hot  3.2  water  in film  mm  during  renewed probe  autumn  1986  celcius  overheat  signal  Instrument)  of  were well  and  and  the  as  to  assuming  that  At  each  2.13).  they  10  a  CR21X  runs.  hemispherical  tip  fixed  from  the  problem  municipal of  probe  runs,  water  -was  rotating  drum  during  well  a  were  followed  as the  converted a  station,  output  by  require  the  flume  minute  to  probe's  to  regarding  seconds  in  velocity  mean  of  interval  interval  One-minute  TSI  the  extraction  similarity 15  a  Scientific  sufficient  log-normal the  analog  allowed  one  Froudian  variability.  degrees  (Campbell  very  would  19  processed  logger  during  is  at  the  Hz,  data  field.  lesser  measurement  during  operated  at  Accordingly,  values  recorder  1239W  a  was  as  values  interval  bear  voltage  voltage  velocity  (equation  in  The  minute  time  level  TSI  measurements,  to  maximum One  measurement  likely  sent  mean  could  a  During  It  sampled  logger.  the  measurement.  flume  was  discharge  using  usual  calibrated  During  probe  from  water  water  the  with  tap.  Wolcott.  ratio.  of  characterize field  F.  data  minimum  the  been  John  the  soft  each  distance  constant  mm  very  reduced  from  module  calculation  The  the  measured  1.5  velocity-area  some  A  stayed  measurements.  had  by  from  operating  the  rod.  at  run.  the profiles,  drawback,  were with  substantially  contamination  The  flume probe  elbow  supply  constantly  the  (7  measurements)  Because  that  via  section  of  Velocities ruggedized  estimated  cross  interval  entry.  only  thus  documented  one-minute  flume  be  one  was  the  profiles  average velocity  as values  distribution. distance  from  the  water a  surface  and  millimetre  could  ruler.  hardly  operation,  be  the  interface,  field  the  water  about  from  level.  construct  set The  runs. with  protractor  mounted  Errors  the  same  4.2  Scale  4.2.1  in  magnitude  General  As field  was  to  present  argued  laboratory  model  scaling  laws.  scale  ratio  from  i.e.  of  in  of  flume  to  the  water-air  surface.  profiles  Hence  than as  were  measured  water  surface used bed  walls  rod  and  under  close  to  using  a  in  order -  a from  2-5  :  2,  order  to of  were  flag  considered  CreeK  read  flowlines  read  i.e.  and  configuration  using  were  field,  Blaney  proper  near-bed  readings the  For  water  final  and  latter  bed.  close  was  the  same  probe  measurements  the  maps  the  the  Kept.  at  the  using  and  above to  a the  be  of  degrees.  strategy  considerations  modelling  conditions,  get  manually  shape,  the  detailed  procedure  as  modelling  the  elevations  to  the  below  same  respect on  too  proportions  Near-surface  determined  from  more  carefully  and  set  not  surface  topographical  flume  mm  measured  size  mm  be  could  all  were  its 2  get  we  water  ruler  a  5-6  surface,  millimetre  of  not  easily  conditions  depth  than  must  could  Finally,  flume.  closer  probe  we  the  water  Because  set  i.e.  although  the  the  in  chapter  conformation exercise The  prototype flume  on  needed width  width  in a  to of  to  strictly  hydrodynamical follow  the model  was  16  times  basis,  undistorted  flume  to  verify  for  Froude  determined near smaller  the  the  banKfull than  that  of  the  up  to  creek. be  satisfies 3.5  about the  Dgg  Bed  in  is  case  of  consideration of  an  the  similarity A  load  (2.26),  (Bray,  of  a  the  came  scale  ratio  using  1982). bed  reach  k  The  material,  =  s  other  which  will  material (recall  sand  many  The  it  to  in  for  a  and  2.5.2).  is  situations  paragraphs  taken  Creek  2.5.1  rivers,  in  were  Blaney  sections  bed  model.  which  specification  which  scale  order  the  to  modelling  this  practical  the  utilisation  follow bed  best  In  describe  material  meet  size  mechanical  requirements. first  sample  that  study  Such  equation  rivers  prevents  undistorted  of  flume.  of  bed  most  procedures  the  detail.  trivial  which  distribution  the  of  scaling  of  not  length  in  is  some  matter  exercise the  scale  material  The  m  gravel-bed  length  discussed  4.2.2  1.6  the  requirements  for  important be  Accordingly  step  consisted limit  following  in of  using suspension  the  scaling  truncating  the  of  it  flow  the  at  the  conditions  criterion  (Parker  volumetric  of et  al,  bed  material  suspended-bed  material  November '1982)  23.  was  The  used  :  V» >  where  V  is  s  Rubey-Watson  a law  particle  suspension  for  November  1.25  mm.  resulted  in  (4.1)  settling  (Dingman,  for  This  1 .0  1984). 23 the  velocity  as  defined  Accordingly,  conditions truncation  was of  the found  about  to 7.6  by  the  upper  limit  be  about  'A  of  the  size  distribution. The  truncated  obtain  a  some  Reynolds than  have  allowed in  Ripples  can  size  i.e.  occur  in  that  these  models  the  Jaeggi  for  procedure  Reynolds  several  to  the  sediment  resistance)  transitional  with  which  5  Jaeggi  also  model  correction  of  in  order  with  regime  of  bed  material  studies,  the  turbulent Reynolds  (1986)  commented  bar  model  shape  would  In  conditions  formation  flow  be  too  that a  as  proposed the  small  (i.e.  in  particle terms, curves  shear for  to  distribution  entrainment critical  a  situation.  size  mechanics  in  minimum  According  improve  the flow  smaller  recommended  to  of  flow  procedure  70).  particle  as size  number  sediments.  to  fully  not  field  represent  5  model  would  percentage  laminar  should  transitional  the  (all  preserved,  certain  with  He  river a  low  respectively  Reynolds  particle.  of  transport in  for  concerned  from  a  interfere  applied  the  number  particles  be is  in  according  (or  can  if  particle  rivers.  considerations,  be  094  model  a  can  number  particle  which  truncated  and  the  gravel-bed  (1986)  particles  of  gravel-bed  above  This  wake  and to  The  the  has  scaled  26).  situation  Reynolds  condition the  in  conditions  of  particle  figure  occur  the  model)  to  Truncation  relatively  conditions  D50  Froude-scaled  which been  the  2.5.2.  distribution  5,  for  entrainment  (see  then  distribution.  likely in  D^,  mm  size  have  section  93  was  sizes  sand  has  and  than  fine  proper  distribution  the  would  very  discussed  model  particle  number  finer  29  distribution  target,  eliminated  5,  size  and in  velocity  those  field  in  the  wake  which  fall  range  when  scaled.  The  81  Figure 26. Comparison of laboratory aodlmont mixture with the corrected and non-eorrrected scaled slzs distributions of the truncsted volumetric sample of Blaney Creek  Sieve size (In phi)  correction It  will  that  procedure now  On  figure  of  the  size  27,  model  the  (equation linearly  for  flow  respect »cr  smaller  resistance  conditions  Froude  scaling  distribution discrepancy 27,  results  finally  is  2.3  mm  around  bed  the  between  the  two •  adopted  correction  curve  is  to  better  reproduction  conditions  present  Figure modelling scaled and  26  also  exercise.  (scale the  in  ratio corrected  the  of  17 size  2.3  in  changing At  and  the  model in  the  the  two  curves  for  model  the  as  in  if  only  grain  size  to  the  corresponding  size  with  difference  the  shown  in  figure  distribution.  coarser  size  factor  mm  those  of  the  to  conditions  reproduced  curves,  r  are  order  Rp>70.  in  grain shear  5<Rp<10,  about  of  model  than  the  distribution  and  the  of  model  The simple  is  aimed  entrainment  prototype.  presents Also  i.e.  Shields  entrainment  somewhat  truncated  a  than  of  scaled  abcissa,  in  for  particles  c  27.  distributions  for  indicates  v„  figure  critical  the  0.05  amount  geometrically give  0.03  Shifting  by  a  that  at  applied.  the  assumed  divergence  curve  in  size  properly  The  than  both  or  are  overlap.  of  at  larger  on  curves  velocities  grains  in  Froude-scaled  we  constant  field  the  for  resistance  the  curves  grains  for  grain  to  of  constant  shown  present  (1986),  and  is  detail.  the  shear  10<Rp<70  the  that  Jaeggi  it  are  dimensions  was  conditions,  model,  scales and  critical  2.25)  and  some  Also,  Following  calculate  in  two  prototype  at  shown.  graphical  described  distribution.  velocities  v  be  is  shown had  the  final  on been  mixture  figure used  distributions  26 at  for  that  used are  the  time)  comparison.  in  the Froude  truncated It  is  seen  that  scaled  the  and  falls D50.  The  D5Q.  Above  the  In  it,  mentioned specific  4.2.3  the  (Jaeggi,  that gravity,  i.e.  Working  Since  is  just  about  and  stage  often  assumed  (Knighton, rivers of  the  small  research  is  Perhaps  the  to  most  be the  it  develop  to bed  greatest  related inherent  shear  to  the  historical  of  is  in  had  component  the  cubic  be same  metre.  in  morphologic  the  bankfull  at  significance  a  variety to  those  bankfull and  assumption statement  in  an  initially  with  this  particularly of  any  a  of range  streams  dominant  from  a  deemed  should  adjusted  latter  associated  represent  it  in  working  the  only  morphogenetic  the A  memory  the  properties,  stress  morphology risk  above  conditions  likely  of  accept  desired  discontinuity  perhaps  equation  the  Although is  is  from  per  some  rivers.  reasonable.  was  a  bear  morphology  the  project to  should  alluvial  dimensionless  that  attempt  to  discharges,  excess  discharge  in  with  departs  sediment  field  the the  mixture  kg  hydrodynamic  long-term  formative  which is  1984)  2700  below of  Finally,  laboratory  regarding  associated  1978)  this  the  actually  vicinity  usually  differences. and  latter  the  than  so  field  (Williams, is  samples  well  distributions  mixture  field 1986)  The  in  finer  assumptions  it  good  being  some  the  sufficiently  size  selected  case,  despite  target  pretty  actually  approximations  reproduces  distribution.  two  is  any  acceptable,  si2e  the  match  curve,  DQQ.  adopted  corrected  between  desired  mixture  for  conditions bankfull in order flat  this to bed.  assumption  high  flood  or  environmental  system, to  as  stated  perform  sequence profiles  The some  considerations  near  decisions  possible  bed  to  must  the  usually  be  Therefore,  the  approach  stabilized  and  transport  which  usually  such  occurred  conditions  were  collect  3.  set  of  case  of  was  to  run  the  a  was  at  the  inlet  mobile until  river.  the  a  bed  condition  running.  velocity  a  it  zero, of  at  that  flume  hours  that  low  more  approached  attained  fact  sediment  the  by  transport  relatively  feeding  few  supported  suggested  in  a  a  The  appeared  without  after  order selected  sediment  chapter  rate  the  apparently  discharge  done  to  and  sediment  flume  on  in  conditions.  also  in  formative  run  had  measurements  material  near  we  were  Therefore,  focusing  bankfull  introduced  of  supposedly  as  at  hydrodynamic  (1963).  experiments  hydrodynamics,  latter  transport  G.G.Simpson  laboratory  pool-riffle velocity  by  When  the  measurements  were  performed. The  next  configuration laboratory creek  pool  of work  bed  the  bedrock  bed  level  was  be  most  those  comparison  not and  well  one  as  to  of  ongoing  an  the  that  in  the  in  the  determining  the  Hence,  control  the  presence  for  the  proximal  to  the  flow  and  transverse  log  obstruction  reproduction advantage  fluvial  the  details  in  processes.  of  Early  the  important  the  boundary  details  site.  bedrock  by  apparent  well-defined of  and  provided  relevant  all flow  the  field  hypothesized  outcrop  as  regard  creek  were  control  Correspondingly that  it  topography  downstream to  Blaney  configuration  creek's of  considerations  of  of  the  Blaney  conditions  processes  at  a  were field  creek  of  judged situation.  site  would  allow  local  scale.  was the  The from The  characteristics  a  purely  of  generic  geometrical  scaling  the  to  creek  a  of  more  the  determined  the  the  slope  accordingly  final  value  the  was  of  the  hydraulic  of  the  resistance  depends  on  reported  appropriate  in  chapter  Another  initial  not  represent  Blaney motivated compared ratio  to  10  banks,  to  at  the  and  The  first  provided (the  field  affected in  by turn,  conditions,  for  as  model  right  bank  beginning  of  resistance  the  hand,  resistance  1981).  the  to  laboratory  creek  and  sinuous  5  the  it  appeared  Blaney  figures work,  depth  hand,  it  of  small  to  other  undercut  (refer  was  rather  as  roughness  of  this  width  the  assumption the  is  with On  did  reproduction  one  channels  (Knight,  to  bank  in  bank  working  runs  described  geometrically  outcrop,  the  and  6)-  banks  were  straight.  configuration  introduced  be  flow  that  the  considering  Therefore, smooth  On  a  especially the  whence,  However,  which,  the  element  that  15  difficult  of  of  was  important  resistance  character  also  materials  controls  slope:  zero.  will  reproduction  assumption  represented  exceedingly  to  boundary  fact  bed  above  also  the  bed  shift  approach.  downstream  imposed  gradient  hydrodynamics.  by  modelling  and  set  a  2.  an  Creek  local,  entailed  specific  upstream  immediately flume  also  although small  built some site  lateral using notional map)  were above. the  performed The  blocks,  roughness. reveals  bedrock  straight  distortion. lego  with  the  Figure a  the  most  outcrop  flume  wall  28  shows  material  Comparison simplifications  was  of  scaled  constraint the which  with  simple  model .  also  figure  5  its  shape.  87  Lego-built  model  of  Figure Blaney  28 . Creek  bedrock  outcrop  Furthermore,  the  between  upstream  the  geometrically.  obstruction  The  important  feature  deflection  of  left  bank  its  field  impinged  at  a  level  of  the  thickness  of  10.3  cm  flush  non-alluvial a  similar  material  compacted  the  saturate the then  the  bed  desired  and  performed  to  to  a  determine  cm,  by  considering  most  of  the  outcrop  and  filled  the  control bed  the  velocity flow  was  order  near  set  or  at  pump  pump  in  rate  the  the  The  however  and  starting  flow  level.  was  gravels  raised  if  the  done  material  pool  Then  Cross-sectional  towards  the  bed  with  gradually  then  one.  of  levelled.  was  upstream  obstruction.  Before  and  the  also  of  downstream  glued  height.  discharge  the  Another  way,  side  proximal  plate  geometrically  and  to  27  This  left  on  reach  about  modeled  cases.  flow was  distance  also  is  This  ratio.  angle  by  was  scaling the  all  incoming  to  the  were  in  field.  channel  via  and  configuration  similar  the  controlled  16  upstream the  the  flowed  study  the in  and  a  Finally,  of  flow controls  was  initial  upstream  width water  ratio  the  occurs  the  incoming  modeled  of  the  downstream  scale  most  as  constraining  and  to  the started  to  first  slightly  below  measurements rate  needed  were to  be  readjusted.  4.2.4  Initial  Bed hours field  of  experience  topography each  site  readjustments  run  with  developed and  morphology. were  and  made  it  adjustments  very could  In one  be  each at  rapidly  a  to  in  compared successive  time  in  order  the  the with  model  first the  few target  run,  necessary  to  discriminate  the  effect  It  was  of  found  considered, banKs  of  the  well  of  some  pool  (refer  to mound  the  stream.  the  mound  cobbles.  2  and  roughness  was  adjustments  important  distal  pool  the  scaled the  was  introduction  scaled glued  did  point  to  not  in  the  creek  laboratory  bed  stream  configuration.  different  stream  configuration  about  10  signs the  m  there right  blocked sediments.  upstream of  an  side by  of an  The  from abandoned  the  work  by  by  and small  to  a  5).  across  boards  lasted  grow  over  24  factor  of  notional  the  of  which  can  be There  would  past.  the  emerged  evidences  outcrop.  large of  either.  inherited  past  have  This  areas  Its At that  from  a  for  a  observed are  some  flowed  channel  organic low  some  roughness.  growth  be  bank  which  hypothesis  the  creek  on  field  bedrock  in  right  sheet  could  channel  state  lego  the  the  in  accumulation  figure  impossible  pool  Some  outcrop  perturbed  of  distal  the  to  all  the  character  discharge  increased  some  morphology  different  and  was  aluminum  in  of  as  value.  produce  result  side  on the  obstruction  right  runs  was  bankline  using  and  reinforcement  if  bankfull  sinuous  the  using  be  roughness sides)  water  it  even  discharge  near  of  pool  to  non-erodible  simulated  those  geometrically  current  amount  proximal  the  of  description,  with  when  flume  its  morphology.  needed  upper  reproduce  local  and  the  site  bed  notional  along  on  field  the  of  downstream  to  3,  area  Accordingly,  this  found  reinforcement  Bank  even  sandpaper  scour  on  factors  necessity  local  order  element  additional  the  mound  in  Even  above  was  them  adjusted  most  hours  some  chapter  The  the  that  prevented  modelling  proximal  conf igurational  amongst  (which  as  each  is  debris around  on now and the  creek  (attributed  decades of  ago)  past  , of  was  further  measurements,  distal  pool  assumed  with  section  3.5).  tested  within  the  to  be  respect possible  the the  incoming  more  several  hours  of  current  creek  configuration  This  study  the  distal  or  running  situation  pool  existence flow  not  along  in  could  bank.  the  run  appropriate  be  and After  configuration,  and  in  the  outcrop  right  latter  reinstalled  result  appeared  removing the  the  at  discussed  by  above  the  riffle  which  flume  the  was  the  (as  from  in  configuration  made  under  shear  over  a  flow  apparent  bed  than  wall  to  fact,  the further  distal  pool  either.  dramatically as  actual  lowest  absence  past was  acted  a  of  However,  new  introduction  level  the  downstream  log  the  order was  must  either  proposes  never  been  to  a  pool  the  at  due  the in  distal a  to  is  pool some of  the straight  however pool  possible related  point  in creek  actual  bed  relict  morphogenetic  which  that  the  to  the  the  the  flume  Creek  log  is  that is  Blaney  transverse  It  distal  reconstitute  understood  that  of  configuration  difficult  be  affected  control.  in  altering  history  which  downstream  bed  in  event  the  the  laboratory  It  internal  flow  water  did  Another  and  three  field  concerning  the  past  straight  forcing  growth  nearly  detailed  by  lower  to  thereby  continued.  any  proposal  discharge,  One  of  above  stimulated  that  formative  contradictory  operations  precludes  the  appeared  deflection  logging  configuration.  emergence  status  field  the  unfortunately  creek  The pool  to  past.  in  the  morphology  walls.  any  scenario or  sense  that  which it  implies  has low  transport the  rate  (at  competence  in  largest  clasts  sorting  hypothesis  flume to  runs, the  it  riffle  the  contrast  to  actual  at  to  scale  see  if  these  of  pool,  for  the the  what  during  process  hours to  nearly  similar  to  the  riffle  growth  is  associated  consists  of  the  the  of  active  over  due  it  lateral  contrast,  several  the  corresponds  the  In  of  foregoing  prominent  those  be  of  the  absence  field.  In  to  the  extension  below  to  the  comment  to  be  physical  models  conf igurational  "abstract  made  about  the As  what  of  of  a  to  and  run.  The  were  excavated  creek  and  14  dig  level  manually  the  13  bed of  a  was  final  morphology.. below),  preserved  and  all the  reinstalled. the  results  relict aim  pointed are  flat  with  on  the  and  similarities  with  the  site  process  above  flow  is  warranted.  the  (runs  described  characteristics  appear  runs  creek  initial  compared  pool  remarks  the  riffle  be  of  Blaney  in  eventual  going  considerations,  the  preserved  the  any  latter  pool  elements  general site  less  since  modelling  deflection  Before  field  distal  of  to  in  run.  period  was  excavated  conf igurational  some  the  not  all  transport  occurred  in a  For  maintenance if  (refer  3.5). that  crest,  distal  then  upstream  stream  only  pool,  would  arrangement  For  even  for  the  it  was  area,  area  of  the  pool  pool  the  the  pool.  light  approach  actual  configuration  proximal In  or  early  the  bed  pool)  observed  whose  distal  the  section  pool  occurred  building  the  was  over  by  in  coarsening  transport  of  the  carried  distal  surface  least  pool  of  this  out  believed historical  of  these  runs  hypothesis,  the  research  by to  Simpson be  the  events".  project (1963), essential Hence,  despite the  the  manipulation  flume,  the  ascertained. pool  status  of  Finally,  is  an  than  project.  In  actuality,  will  still  4.3  Laboratory  4.3.1  Bed  the  on  results  and  morphology  two  runs  excavated  distal  pool  will  be  The  flow  latter The  two  will runs  slightly 13  (figure  bed  configuration  approximately procedures.  to  same the  appears November  to  slightly  different  23  laboratory and  principles.  to  field  and  14)  introduced as  the  discharge,  of  figures  features  the  order run  on in  29  the the  bed, field  assumption the  no-feed  respectively. of  paragraphs  to  show  14  (figure  and  below.  30  that  (figure  5). the  procedure  of  a  30)  final  can  be  laboratory  the are  and  map  current  which  regarding  the  configurations  topographical  the  with  paragraph.  hours  initial  following  from  found  one  this  the  The  in  in  characteristics in  developments.  is  support  research  situation  13  200  material  had  features  laboratory  and  pool  runs  and  analyzed  note  general  100  bed  replicated We  field  fully distal  this  similarity  (i.e.  further  such  be  the  of  conformation  be  29)  the  considered  about  and  distinct  run  the  lasted  dynamics  run  thus  14  from  in  conformation  from  and  to  goals  of  their  cannot  regard  distal  verification  configuration  pool  of  the  results  13  the  comparison  The  Runs  distal with  clarify  the  creek  learned  drawback  will  allow  actual  lesson  a  characteristics  the  situation  interesting  rather  with  the  the  exercise  flow  done  existence in  turn This  similar situation  significance and  of  the  of pool  Topographical  map  of  Figure 29. r u n 13 f i n a l  bed  configuration  Bank I i ne u>—  Countour Excavated  4. 4  4. 6  Distance  from  4. a  flume  inlet,  5. O  in  6. 2  5. 4  (  elevation  in  cm  )  area  5. 6  5. a  metres  CO  Topographical  map  of  Figure 30. r u n 14 f i n a l  bed  configuration  • Bank 1i ne  •\.o—  Countour Excavated  4. 4 Distance  4.  ii.  6  from  flume  6.  8  inlet,  in  metres  0  5. 2  5. 4  (  elevation  in  cm  area  5. 6  5. fl  excavation. Boundary exception  of  obstruction 13  and  and  conditions the  to  this  the  the  proximal  the  distal  at  an  pool  in  had  be  simplification  small  dumping 5.55 by  sediment  in  m)  of  hand.  depend In  of  the This  on  the  consists  of  shoaling  area.  similarity distal  of pool  sediment  (5)  field  and  shape  the which  was  that  laboratory of  the  discussion stream represent  the  area  is  field.  The  topography  was  degree  of  of  considered  for  to  be  appears simply  by  bed  depend  on  grown  herein  by  area  (i.e.  feature's if  of  the  pool  will  (2)  over of  the the  material  growth low  may  intensity.  main  further  test  below  introducing  topography  proximal  various  to  distal  area  main  the  be,  topography  it  hydrodynamics  should  the  even  below  Whereas  that  latter  cross-over  it  31  site's  created  supply,  also  the  the  the  linear It  cross-over  14  run  of  was  Also  sediment the  The  and  in  14.  unavoidable  not  since  area.  riffle  below  is  field  suggests  the  however  simulated  more  run  run  scaling  (4)  the  upstream  summary,  between  Note  the  in  the  Figure  than  that  the  the  for  the  considering  be  shrink.  and  and  the  downstream.  wider  field  bar  with  supply  with  to  to  perhaps  preserved  by  accumulation  upstream  is  between  elements.  (6)  with  prominent  (2)  further  run,  of  more  configurations  location  introduced  comparison  pool  pool  14  sufficient  conf igurational  proximal displaced  been  each  downstream was  final run  for  latter  distal  topography  to  strict  in  homologous  judged  be  and  pool  closeness  the  to  initial  the  the  the  same  area,  The  excavated  the  the  (3)  flow.  caused  the  shows  mound  cross-over  caused  were  difference of  run  14  extension  and  consider  the  riffle  and  hydrodynamic  scaling  done  4.3.2  Flow  measurement  Only because  the  those  and  geometric data  (see  to  =  the  3.5  Therefore regime  and  by  the  the unity. from the this  In  fact,  close  Let  with  water  seven same  (in  actuality  dysfunctional  renders The but  the  slope  risk this  The are  pairs  exact  model  may  then  some  uncertainties  be  Table  3.  sampling (accepting  rough  appropriately  further factor  the  supported  (table  column 7  was to  X  be  exactly  measurement  be  related  of  obtained  correspondance to  3). presents  within  which  mainly  23  hydraulically  always  said  The  met.  last  in  for  is  appears  error  bankfull  material  is  estimate  of  in  (2.23)  the  the  2.5.1.  values)  friction  which  that  November  accordingly  3.  elevation the  in  event.  criterion  and  bed  situation  table  surface  14  allow  20  section  equation  were  of  values,  longitudinal  quantity  coincidental).  target  in  from  was  latter  on  The  surface  forces  concentrate  The  the  to  scaled  cross-section  by  model  the  the  run  those set  correspondance  us  ratios  the  resisting  reproduced.  and  flume  verify  field.  homologuous  using  in  to for  of  considered  November  presented  parameters  conditions  flow  the  be  the  scaled  conditions  was  an  in  essential  of  values  ^90>  a  is  met  for  these  below),  s  be  hydraulic  provided  According  it  can  depth  for  those  to  and  are  flow  entrainment  reproduced  conditions  conditions  insufficient  instance,  flow  discharge  bankfull  measurements  first  general  k  was  profile  the  conformation  near  there  velocity In  herein.  of  rather  very  mildly  to  slope  Table  3  M e a n h y d r a u l i c a n d g e o m e t r i c p a r a m e t e r s f r o m r u n 14 a n d c o m p a r i s o n w i t h t a r g e t v a l u e s as f o u n d f r o m Froude similarity principles R u n 14 value A  Target value from Froude 1 aw ( 1 / 1 6 ) B  Ratio A/B  D i scharge ( l s ~ )  5.21  4 . 88  1 . 07  Mean ( cm  33. 1  32. 5  1 .02  Mean w i d t h ( cm )  43.0  43.8  0.98  Mean ( cm  3. 66  3.43  1 . 07  3.13  2. 97  1 . 05  0.0102  0.0102  1 . 00  0. 55  0 . 56  0.98  n/a  n/a  0.225  1 . 02  1  velocity s ) -  1  depth )  Hydraulie ( cm ) Water slope  radius  surface  Froude  number  Reynolds  number  8000  Fr i c t i on  factor  0. 229  measurements  do  considerations. mildly a  for  sediments (the  higher  than  ignorance a  can  now  and  possible  to  steady all  and  over  structure  situation The  large  areas 37).  figures. profiles  a  of  width  bank  later  than  the  differences  run.  did  must  was  Other  roughness  issue  is  over  the  the  pool,  number  slightly  items  not  greater as  ones.  like  seem  the  to  Figures in  was  under 32  the  the  and  33  distal  figures  in  is  velocity It  profiles  These  This  the  pool clearly  pool  somewhat  flow  similar  to  field.  within  comments  field  profiles  profiles  and  of  of  variability  the  of  shape  laboratory.  riffle.  in  riffle  the  the  velocity  subdivisions  First,  the  with  more  number  the  of  respectively.  there  general  the  channel  discharge  the  bank  larger  of  riffle  Two  in  the  much  observed  further  lower  for  dimensionless  than  during  conformation  conditions  that  allows  consider  the  that  that  difference.  measure  the  fact  could  facts  smaller  the  which  which  sinuous  slightly  of  (1980)  and  the  these  that  the  17)  actuality,  value  others  perhaps  of  of  to  sources  of  are  In  scaling  their  flow  show  and  strict  ratio  simple  target  significant  profiles  suggest  the  the  of  We  the  from  are  study)  require.  and  Possible  introduction  the  prefered  Dhamotharan  scale  the  of  would  arise  make  to  a  development  is  dysfunction  using  progress  mostly  statement  from  mild  due  ratio  further  connotation.  (scaled  the  scale  model  this  latter  any  latter  geometric  account  allow  The  distorted  has  in  not  of  sampled the  the  from  variability  mentioned  site pool  emerge  in  in  above,  the into  (figures the the can  laboratory upper  34,  latter  35  ,  36  series  of  of  the  shape even  and  be  better  100  Figure 32. Dlmenalonleae velocity prof Ilea In pool, run 14 1.00 •o *  'e  0.80 0.80  -\  0.20  H  0.10 0.08 0.08  H  0.02  0.01 0.10  0.30  0.80  0.70  0.80  1.10  1.30  1.80  Point / Height averaged velocity Figure 33. Dlmenaionleaa velocity prof ilea over riffle, run 14 1.00 0.80 0.80  H  0.20  H  0.10 0.08 0.08 -4  0.02  0.01 0.10  "i 0.30  0.80  0.70  1  1  1  1  1  1  r  0.80 1.10 1.30 1.80 Point / Height averaged velocity  101  Figure 34. Dlmenalonleea velocity profHeo Downstream part of riff la, run 14 1.00 0.80 J3 >  0.80  0.20  H  0.10 0.08  0.08  H  0.10  0.90  1.10  Point / Haight averaged velocity Figure 36. Dimenelonlea* velocity prof ilea Upatream part of riffle, run 14 1.00 0.80  H  0.80  0.20  0.10 0.08  0.08  i 0.10  0.30  0.S0  0.70  r  0.80 1.10 1.30 1.60 Point / Height averaged velocity  102  Figure 38. Dimensionless velocity profile* Downstream part of pool, run 14 1.00 e o  0.80  0.80  -  0.20  -  0.10 0.08  0.08  -  0.90  0.10  1.10  1.30  1.80  Point / Height averaged veloeity  Figure 37. Dlmenalonleea velocity profllea Upstream part of pool, run 14 1.00 0.80  0.80  -  0.20  -  » o e e  C  0.10 0.08  0.08  -  0.10  0.30  0.80  0.70  0.90  1.10  1.30  Point / Height averaged velocity  1.80  appreciated. are  less  Second, Kinked  profiles  ' is  may  over  much  In  for  the  the  banks.  that  distal  variable  pool  expected  since  constitutes in  area  of  the  velocity  spaced  grid  (refer  to  gradient  layer  mostly.  varied  from  deviation  riffle.  The  (2)  Observation  (1)  proximal  pool  which  (2)  possibly  Observation which  discussed 3,  sixteen  to  test  with  vary was  not  a  that  the be  actually is  m  shows It  the  not to distal  variability  test 4  5.16  of  X  4,  along  local  five the  shows occurs  shear  on  that  of  at  performed  in  wake profiles  and  standard  local  considerably,  the  those  2.76  a  velocity variability  for  from  mm flume  dimensionless  average  Therefore, to  more  downstream,  A  profiles  near-bottom  Pa.  appears  38  stations.  Pa,  (1)  are  related  consider  on  at  velocity  9.71  now  made  crest  Figure  the  us  was  riffle  of  the  measurements.  profiles  30).  in  by  below). let  profile  the  2.54  occurs  is  are  should  the  chapter  same  part;  of  0.55  shear  riffle  extension  Internal  internal  the  37  part  the  of  of  to  upper  figure  in  pool.  34  be valid  engendered  riffle's  near  for  lower  the  structure  the  velocity  profiles  the  effectively  in  in  in  part  river  variability  figures  pool  observations  flow  (further as  the  in  of  upper  in  shearing  Just  variability  than  source  from  the  comparative  actually  flow  profiles  of  latter  may  complex  the  character.  extensive  pool  in  the  the  another  the  shape  from  pool  observations  the  These  indication  the  situation  whereas  distal  contrary  field  capricious.  is  shape  is  uniform  riffle  the  profiles  situation  the  first  Specific  in  the  addition,  velocity  the  a  that  inherited.  in  more  represent  hydrodynamics  as  least the  scale, over distal  the the pool.  Flour* aa. Local ahaar atraaa variability taat Dimonalonloea valoclty proflloa, run 14 0.80  - r —  °-  3 0  .  0-80  0.70  0.90  1.10  1.30  Point / Height averaged velocity  105  However, the  it  pool  appear  appears is  at  to  profile  least  be  variability  reasonable of  more  of  internal  particle not  that  the  grid  test  that  may  be  locally  have  be  not  be  a  through  study  distribution  (18  Pa  of  stations).  ratio,  give  field  flow  we  apparently  laboratory,  the  than  indicates  laboratory estimates riffle  and  actual under  that  suggested  Figure shear  estimate  of  the  larger set  accurate most  39  presents  effects field  variability we  did  not  over a  suggest  conditions  are  the  shear  in  i.e.  the  scaling  nearly  in  the  greater  bed  of be  the 3.4).  riffle  much  is pool  (section  conditions may  of  the  the  mesurements.  significant  by  stress  covers  to  map  Pa  respectively, shear  distribution  average  2.636  difference  the  a  The  and  stress  appear  for  fact  the  shear  multiplied  which  field  bankfull  the  by  since  of  although  profile  near-bed  restrictive  absolute  16  possibility  variability  laboratory  when Pa  data  the  consider  velocity  stations)  42.18  would  near  more  (26  get  local  of  suggested  estimates.  values,  the  results  However,  area.  the  the  by  at  internal,  and  the  hot-films.  the  These 49.94  as  the  of  riffle  uniform  Although  area  the  in  must  in  profiles  gradient,  temporal  temporal  near-bed  over  the  includes  array  consider  suggest layer  pool  to  spacing  one  variation  since  regard  wake  important,  the  close  Finally  investigated  the  to  also  rod-mounted  magnitude  the  verified.  that  With  on  However,  Next,  3.121  shear,  effects  could  could  same  appears  this  observations.  the  suggest  variable.  measurements  individual  to  the  field  smaller  than  Accordingly,  the  that  field  overestimated  shear  for  the  of  this  pool. point  in  the  context  Figure Near-bed i n t e r n a l v e l o c i t y sampling  39. shear e s t i m a t e s at s t a t i o n s , r u n 14 Banks Riffle  Note  4. 4  Distance  4. 6  from flume  4. a  inlet,  5. o  in metres  6. 2  : shear  5. 4  units  are  crest Pascals.  107  research unit  project  area  theory  bed  to as  before  existence  of  also  from  Considering  such force  in  do  not  through  the  sequence  from  figure  the  latter It  remains  that  tenet  the  to the  made  about  the  current  can  of  a  For  the  riffle.  effectively be  rather local  to uniform  variability  of  In  the  tractive run  low  of  pool  and  region,  the  and  to  shear  attempted  distal  overshadows  14  part  be  compared  units,  higher  former  very  to  bed  upper  may the  we above.  bottom  that  the  be  as  instance,  which  part  of  in  to  difficult  limit  observation  upper  estimates  paragraphs  reversal  generalizations  of  two  in  unit  measurements.  shear  the  the  bed  considerable,  concentrated  the  the  extremely  within  further  regarding  at  be  become  field  be  deserves  spaced  appendix).  the  only  appears  seems  the  addressed  discussed  shear  would  area  shear it  may  concern  39  downstream  internal  it  support  The  supporting  laboratory  closely  test  the  be  from  grid  of  by  results  per  in  estimates  distribution  variability  pattern  reach.  shear  local  (described  force  decisions  configuration  can  sufficiently  advocated  various  shear  easier  reality,  any  as  in  the  this  near-bed  reproduced,  the  conclusion  is  the  found  recognize  and  the  patterns  that  the  of  effort.  any  offers  39  confirm  as  of  Discussion  magnitude  reasonably  scaling  variability  attention  Figure  be  modelling  Local  scale.  the  well  material  hydrodynamic  the  that  appears  similarity the  is  in  other these  the areas.  general  statements. This rationale Perhaps  situation behind one  and  source  warrants the of  some  consideration  characteristics variability  comes  of from  such the  of  the  variability. intrinsic  characteristics above,  of  perhaps  significant  however  equation  area  more  for  near-bed  local  shear  flows  spatially  also  over  reported  brief  consideration  characterizes  the  13,  despite  a  at  the  discharge  calculated  from  velocity  1.36  for  the  difference distal  comes  pool  although  as  spatial  in  coverage  riffle two  spatially cases  (i.e.  at  whether  averaged the  14 was  field  or  shears and  or  14.  large  were  not  run  13  flow  further  shear.  was  Run  performed  internal be  shear  3.26  Pa  shears  measured  and  shear  The in  for  Because  level. the  roughness  (1949).  local  of  is  methods  respectively.  comparable.  detailed  flow  estimates  pool  the  correspondance  Samni  to  that  are  from  internal  found  not  estimate  the  Average  patterns a  given  relative  shear  distal  the  compared  conclude  run  within  essentially  configuration,  was  fact  be  13  run  the  units  to  as  and  differences  difficult  average  riffle  morphological cannot  in  profiles  from found  the  run  different  same  Pa  of  is from  where  El  It  estimate  uniform  and  and local  project.  is  high  have  single  Close  and  Einstein  variation slightly  which  relatively  by  a  shear  pool.  averaged  basis  shear  average,  distal  local  significance  Pa,  shear  do  this  flow  3.13  the  estimation  was A  in  in  suggested  bed a  of  some bulK  is  internal  than  the  the 14  on  averaged  bear  As  the  tested  spatially  must  run  on profile  be  instance, for  uniform  between  a  flows.  significance  not  that  For  (2.16)  riffle  physical  coverage  units.  velocity  could  expected  roughness  particles  the  the  This  intensive  bed  on  reduce  measurement.  relative  individual  effect  thereby  an  high  run of  different. measurements)  pool  and  13 some  within  Therefore,  distal  the  the it  is the  Nevertheless, tend  to  show  109  that  distinctly  greater  average  shear  takes  place  over  the  riffle. Finally, can  be  that  in  the  field a  introduced  Surface  test  of  specifically conditions  addresses  the  dynamically  observed and  of  coarsening in  a  associates  combined  is with  confirm  that similar.  similarity  flume  is  variety (e.g.  finest surface  and  widely of  if  transport  field a  for  the  material  of  of  the  et  al,  surface  represents programme.  a It.  of  entrainment  there  was  particles) layer  excess of  and  would  bed likely  not  be  model.  distributed  laboratory  Parker  the  modelling  (the  of  conformation  situation  the  2.5.2)  class  the  and  reproduction  (section  bed in  structure  hydrodynamic  of  the  certain  equivalent  Surface  and  characteristics  frequency  excavation  hydrodynamically  characteristics  success  a  sediment,  the  the  for  one  validate  pool  flow  characteristics  field  force  21, to  further  are  channel  section.  the  model  the  shear  flowlines  at  appears  and  the  the  figure  reproduction  of  of  the  with  macro  situations  in  by  flowlines  This  internal  material  between  further  Parker  the  comparison  it  the  Its  next  bed  the  configuration  test  the  shows  that  flume  final  in  The  been  of  and  However,  the  the sense  scaling  revealed  similar.  reproduced.  appropriate  materials  40  are  of  as  comparing  patterns  adequately  4.3.3  Figure By  simplification  approach  shear  -  structure  discharge.  realizes  the  flow  compared.  forming  the  the  mixture  experiments 1982).  has by  G.  Coarsening  Figure Near-bottom  and  40.  near-surface •  flowlines,  crest  Near-surface ~ Near-bed  Distance  4. a  4.6  from  flume  inlet,  5.0  in  metres  6.2  5.4  14  Banks R iff1e  4.4  run  5.5  flowlines  flowlines  Ill  appears  not  particle  sizes  sizes  in  to  be  related  but  rather  transport materials,  equilibrium  transport.  (Parker  et  al,  constitutes armour  a  that  formation  were  surface  gained  10  X  were  disposed with  where  the  and  collected  pool  and  coarser  riffle  than  the  were grid  at  In  and  stones.  scale bed  steady  that  A  flow  of  the  would  thus  during  bed  visual  during  as  coarsening  model  particles  for.  the  Known  Reproduction  occurred  appreciation  run  the  their  14  It  samples pool,  but  the  D50  at  can  two  be  but  are  seen  that  the  is  small,  not  quite  of  the  in  pool, a  the  same  side 50 ruler  calipers.  on  figure  combines  riffle  a  collected  with  difference  the  by  were  shown  actually  side  using  measured  exercise  using  the  stones  were  curve  riffle  In  spacing the  b-axes  is  set  same  sampling  the  collected.  cases  sample  over  was  were  both  the  sampled  which  stones  'combined'  riffle  of  which  200  from  the  in  become under  some sediment  presence  has  phenomenon. in  various  indication  accounted  space  randomly.  results  an  of  31.  cm  tweezers  The  bed  materials  Hence  their  which  was  properly  1  to  the  development  interactions  figure  cm,  locations. stones  1982)  surface  10  Armour  entrainment  regulate  process  coarsening  from The  a  characteristics  indicate  of  to  proportion  mobile  layer  preferential  acts  in  subsurface  to  the  pool  between being  way  41  the  slightly  as  in  the  field. In are  from  to  65  (refer  general, 3.41  to  mm,  i.e.  to  table  4.06 slightly 2).  mm.  Scaled  coarser Figure  surface up,  than 42  this  in is  for shows  the  laboratory  equivalent the the  field  to  54.6  situation  grain  size  112  Figure 41. Size distribution* of surface bod material sample* run 14  -3.0  -1.0  1.0  3.0 Sieve size (In phi)  113  Figure 42. Grain alze distribution, run 14 Initial and final aurfaea materials 1.0  -,  —  Grain size (In phi)  114  distribution  of  the  material  at  surface  coarsening  particles the and  the  in  ratios  end  a  n  d  compare  well  with  correspondance  suggests  quite  the  the  in  field  work.  Figure  compares  field  equivalents. from  the  over  grain  sizes.  all  riffle  samples  coarser  in  90  a  the  from  the  various  surface  distribution  is  size  distributions  relatively  close  perhaps  correction of  above  finer  than  wanted  note  that  the  run  corroborate  the  foregoing used  to  were  not  first  13  latter thing  discrepancies sample  pool  the  surface  geometrically  of  D50  n  finest  samples  It (not  as  so*  shown  were  flume of  seen  also  as  Coarser of  riffle  well  well  mixture.  are  is  scaled  very  part  flume  in  surface  because  whereas  D75.  probably  materials  the  samples  This  their  pool  surface  the  These  field  expected  to  1.89  1).  compare  below  surface,  procedure  with  site)  the  be  finer  is  scaled  the  applied  above  seem  The  to  of  (table  no-feed  comparison  for  that  mixture.  samples  that  seen  6.15,  data  and  a  surface  final  transport  sampling  the  the  the  especially  size  easily  initial  field  supports  characteristics  and  the  and  distribution  be  the  entrainment  sediment  reveals  of  respectively  those  size  truncation  can  For  e  for  However,  flume  r  than  downstream  further  It  situation.  Flume  (actually  that  selective  that  laboratory 43  the  D  coarser  and  run.  no-feed  times  low  the  involved  50  D  mixture  of  this  Dig. 1.16  initial  the The-  to  be  sediments  worthwhile herein)  to also  observations. to  consider is  sampling  sediments similar.  in  in  More  order  to  assess  limitations. the  field  fundamentally  The and  the grids  laboratory  samples  are  115  Figure 43. Grain alia distribution comparison Run 14 snd field (seslod) surface aamples 1  -i  •  m-  Graln alze In phi  Flume surface —I  •O-  —A—  •X--  Field surface (acaled)  Flume riffle Field riffle (acaled)  Flume pool Field pool (acaled)  116  always  approximations  well-known  that  the  surface  This  reality  may  also  that  there  is  adjusted  for  resistance  modelling  purposes  some lower  corresponding  field  ones  distribution  to  size effects  may  selected  arise  shear  that  and  further  closer  to  field The actually  stress lower  than  the  of  the  part  Finally, coarse  underrepresented  fact  laboratory  coarser.  fact  the  additional  material  from  the  in  the  start  (see  26). Perhaps  some  operating  laboratory  work  assumption  that  single  restricted  or  development Perhaps could  the have  above  have the  of  this  decision been  In  significant  bed  morphology  range  of  to  the the  is  similar  However,  field  of  and  mainly  the  well.  determined  may  not  have  The via  a  allowed  characteristics.  feeding the  the  as  surface  sediment  similarity  for  influence  discharge  ignore  made  to  the  arguments  the  size  laboratory  seem  system presented  distribution to  constrain  eventuality.  summary,  distribution  a  detrimental.  between  latter  assumptions  exactly  regarding  percentiles  size  the  and  laboratory.  the  the  1987).  laboratory  of  get the  in  encourage  become  was  in  critical  would  from  to  al,  some  truncated  order  which  sediment  consists  was  particles  dimensionless  mixture  figure  in  flume  is  to  et  that  element  conditions  finer  experiencing  fact  sample  entrainment  of  the  finer  it  limit  (Church  the  Another  volumetric  or  possibility  for  Indeed  lower  sampled  for  coarser.  degree.  practical  be  critical  account  field  certain a  may  more  appear the  a  exists  materials  partly  samples  to  despite  some  characteristics  minor of  the  discrepancies, field  and  the flume  actual can  be  117  considered  close.  frictional a  material  run  It  bed  from  field  the  in  flume  which can  be  average  from recorded  on  reproduced  in  the  characteristics  These  figures  versus  the  if  relationship, the  latter over  three  (3)  actual of  the  any,  was  appears  that  greatest  deviation  are  suggest riffle  from  a  the  greater  macroflow the  at  the  each  as  an  In  bear and  velocity  velocity  (2)  which are  the  logarithmic  the  maximum  riffle  particular  the  respectively.  a  turbulence  structures  average  versus  relationship,  the  the  maximum  minimum  minimum  this  of  and  unit  height  at  turbulence  graph  the  and  measurement of  a  riffle  linear  minimum  index  present  (1)  measured  point  period  greater  area.  specifically  one-minute  things:  both  not  minimum  relative  for  those  characteristics  the  and  bear  the  deviations  the  for  pool  height  point  45  the  versus  and  upon  and  the  relative  site  However  recorded  velocity  suggest  velocity  project.  44  for  study  were  looked  within  height,  general  the  depend  that  dysfunction,  on  were  deviation  The  that  this  Figures  velocity,  mostly  suggested the  that  laboratory,  of  characteristics.  maximum  which  appropriately  satisfactorily  and  limits  velocity  relative  therefore  characteristics  maximum  values  were  and  considered  stream  observations  Turbulence  the  the  be  small.  Extended  within  is  material  relatively  also  scale  reproduced  surface  4.4  of  length  laboratory.  model  must  characteristics  bed  the  It  stations.  intensity  in  study, bring more  it the  active  118  Figure 44. Deviation* from one-mlnut* average velocity Maximum and minimum value* in pool  >  a  0.00  0.20  0.40  0.80  0.60  Relative height Figure 48. Devlatlone from one-minute average velocity Maximum and minimum valuea over riffle 200 190 180  •  max  170  +  min  160 180 140 130  • 0  120 110 100 90  l  80  W  70  •  •  +  • • •  60 80 40 30  •  20 0.00  0.20  0.40  0.60  + 0.80  Relative height  119  over  the  riffle  exported riffle  area  from area  Similar  the and  than  extremely  macro-turbulence  before  for  sequence  distal proximal  case  help  the  pool.  reaching  the  could  through  the  turbulent  dissipate  measurements  pool-riffle  over  the pool.  fully  the  sequence,  into  distal  a  clarify  are  pool  the  of  These  alluvial  question  of  as  raised  by  Rood  the  results  from  dye  near  the  (1980). It  is  injections right  worthwhile at  the  banK.  existence  end  Flow  of  a  interestingly  was  noted  (see  figure  21),  was  right  banK  above local  main  line,  along  distal  the  site  laboratory. success  of  Injection line these  dye  pool.  field  revealed  the  could This the of  over  apparent  divergence  phenomenon  and a  exercise  near  occurred,  the of  right  any  bed  at  would  near  revealed a  revealed  that  of . the  shear,  modelling  at  the as  few flow.  of bed.  though  hold  within  the  from  the  observed  position  the  main  indication  the  appear  event  depth  the  current  flow  shearing  further of  distal  observations  further  and  the it  riffle,  longitudinal  reproduced  scaling  at  the  (within  the  These  and  More  dye  banK  the  bank.  detected.  cross-over)  with  to  The  high of  the  the  flow  injected  23  the  to  confirmed.  through  Injection  injected not  be  line  (near  pool  were  November  close  represents  dye  shear  mixing  was  be  could  pool  right  Thus,  vortex  any  did  distal  40  detected.  flowed  body  the  figure  the  distal  when  in  a  during  the  dye, water  wherever  of  without  i.e.  face  also  briefly  14  of  slip  water  centimeters)  the  run  presence  which  Conversely,  of  riffle  the  the  describe  patterns  pool,  that  to  in of  the the  strategy. the  shear Although  they  had  120  no  morphogenetic  since  the  feature,  latter  as  merely  from  the  not  discussed  start.  along  the  right  of  proximal  pool  travelled  on  only  distal  in  them. truly  to  be  transport  site  if  there  the  to  for  imposed  would  morphology  preservation  by  riffle  face  and  each  single  run,  the  of  the  the  creek  scouring  The  of  coarsest  was of  large  material  developing  riffle.  to  entered  enough  distal  the  to  pool  hydrodynamics  and  particles  finest  materials  the  flow  while  the  entrained  shear  the  excess  if  with  main  body  of  was  set  at  bankfull  no  at  To  the  evacuate  would  appear  imposed  by  associated  the  0.01  The high  research  discharge).  would  develop  is  issue,  sediment had  actual The  to  question  flows this  same  (the  sediment  obstructions  approach  the  general  bedforms  straight). shear  3.  the  were  performed  near  relict  the  obstruction  face  finest  the  asked  were  chapter  the  the  concerning  be  channel the  a  structure  pool  along  pool  the  sediment  routes.  Now, may  an  during  preservation  linked of  sediment  observed.  of  the  the  configuration  it  side  which  Hence  flow  help  development,  be  along  Accordingly,  to  distal  represent  macro  may  sorting  could  mostly  pool  pool  lateral  the  it  to  the  bank.  upstream  phenomenon  The  adjustment  entering  to  seems  above. an  the  respect  and  Nevertheless  of  During  with  dug  represent  some  moved  was  we  then  routing  significance  been  in  the is  Blaney flow  low,  additional  mixture  (run  accomplished.  slope  value  flow  rate  conditions, Creek  (i.e.  especially  rather an  transport  in was  the near  study if  valid  as  since  discussed  flume 15)  the  in  run  was  after  the  flume  bed  The study that  reach  at  of  run  14  (see  table  geometric no and  the  from  six  run  was  2.66  The was  and (not  occurred.  presence  of the  bed  at  The  slope lower  run  about  two  to  slightly  appeared than  in  run  and  Pa  respectively.  2.56  analyzed),  to bankfull  no  appears  the  flow,  flow.  14.  via  The  Although  that, no  days  and and  increase average  uniform  planar  it  hydraulic  lasted  profiles  Therefore,  obstructions  information  15).  velocity  developed  on  for  depth  sediment  develop  complete  developed.  average  formulation armour  for  parameters  bedforms  shear  4  flow a  bed  segregation  of  without  undulation  the would  122  Hydraulic  Table 4 geometric parameters  and  D i scharge ( 1 s-1 )  5.10  Mean v e l o c i t y ( cm s )  41.0  Width ( cm )  47.0  Mean d e p t h ( cm )  2.64  _  1  Hydrau1i c ( cm ) Water surface Froude  r a d i us  2.37  0.011 slope number  Reynolds  number  Friction  factor  0.81  7000  0.13  for  run  15  123  Conclusions  5.0  The  present  undistorted  physical  similitude in  study  small  to  some  detailed  gravel  processes  and be  (1984)  viewpoint  taken 1,  appear  was  not  studied  Concurrently,  relatively future  characteristics and  effects  undertaken.  shear was  This  issue  small  the  the  valid  for  of  pool-riffle,  nature  some  of  the  measurements,  (1978)  others  and  despite  Hence  and  research  intensity  that,  to  of  verification  a  revealed  Zimpfer  macroflow  of  the as  the  field  claims  well  (1987),  as  of the  introduced  geomorphological  local  variability  estimates  over  shown  deserve  must  studies  (notably of  field  specific  of  subject  roughness  oriented  be  principles  to  for  that  in  system  herein.  and  research.  process  to  the  profiles high  Schumm  the  reproduced.  and  hypothesis  transport  A  related  limitations  Mosley  by  low  Creek)  convincingly  and  of  quantities  mostly  the  on  rivers.  (Blaney  our  alternative  case  size  variability  can  Knighton  velocity  the  stream  environment  which  for  based  reasonable  hydrodynamic  uncontrollable  chapter  a  intermediate  bed  confirmed  modelling  represents  geomorphology  has  to  probably designed  a  be  river  variability  structures  in  the  bed  some  attention  tackled  before  to  temporal  in  pool-riffle  study or  of in any  salient  intermittency) streams  can  be  The  present  research  also "generic"  strategy  designated  as  sequence,  guided  a  model" full  the  object  size  This  by  phenomenon,  pool-riffle  and  present  part  this  "specific"  represented  shift  from  lesson  from  the  very  important  specifics  (the  sense)  cannot  be  considered  that  some  pool-riffle  features  discoveries  in  lesson  the  on  nature  main  reach  development  transport appears  of  of  some couplet.  do  this  whether  the  relict.  In  had  "generic"  The  the  to  be  to  a  more  situation  is  that  in  low  of  aspects  of  of It  the  streams. transport  Creek found  also  In  the  intensity  appears These  comprehensive  as  by  that  but  do  tool  for  perspective, the  historical  laboratory  development  obstruction  controls by  and  a  another  made  case  it  type.  and  riffle  to and  Gallinatti(1984)  provided  mechanisms  Simpson's  investigations  From  appears  Blaney as  this  modelling  the  in  model:  fundamental  contribution  observations  intensity that  a  location,  understanding  latter  generic  are  topic.  interest.  flow  a  "generic"  understanding  of  and  Lisle(1986). the  is  a  geomorphological  pool-riffle  the  in  a  of  represent  to  thread  of  concept  the  elements  river  represent  the  on  experiment  for  fact  invalidate  research  the  "generic  to  conditions  conf igurational  (1963)  these  a  pool-riffle  stream  a  pool-riffle  In  question  boundary  scaling  model.  historical  not  a  failed  the  a  features  the  prototype the  key  Creek  raised  of  for  prototype.  case,  Blaney  the  demonstrate  certain  this  of  in  situation,  manipulated:  in  this  sequence  field  reproduce  model  spontaneously  A  to  to  modelling  particular  is  particular  intended  additional response of  combined  Blaney with  of  of the pool and  elements very Creek,  low it  preferential  transport  routes  Above lies  in  for  all,  the  the  generic done  in  effects  for  is  made  can  generalized  Generic to by  scales  details  of  the  these  the  family  programme  in  impossible,  to  realized  the  aspects thorough  of  reach  may  not  to  can  in  field  to  of  scale  interpret  river  geomorphology  be  fact  laboratory bed  used  to  said  The  fact are  material. guide  exact  be  are  determined  of  reproduce  situations  of  observations  prototype  the  river  concept  consideration  situation.  in  a  limitations of  field lies  of  gravel-bed  the  the  boundary  to  be  part  importance  that  of  measurement  impractical,  experimental  river merely  herein.  by  the  However,  of  indeed  that  the  with  laboratory  for  be  of  particular, a  numerous  could  be  experimentalist In  vehicle  rapid  could  time,  the  combined  is  potentially  processes.  characteristics programme  assertion  period  manipulation  was  pool-riffle  an  problems  short  controlling  exercise  such  river  relatively  sequence  conformation  the  fallout  allowing  pool-riffle  is  into  situations  nature  tools  perform.  a  factors  as  many  on  conditions  field  models  arguments  immediate  in  of  project  gravel-bed  used  fluvial  prototype  Such  and  in  the  object  reach.  proper  pool.  legitimate  quantitative  practical  by  a  the  conceptual  progress  and  and/or  model,  same  An  family  economical  but  which  models  some  "generic"  model  of  be  are  embodied  which  situation  themselves  a  to  model  restricted  flumes  be  distal  research  full-scale  can  according  the  this  studies  to  fact  of  of  model  a  behaviour.  basically  contribution  respect  emerging  modelling  preservation  that  with  This  the  main  recognition  research  situations.  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Hydrology  Inter-  Publication  Appendix:  A.1  Bed  General  A  consists the  of  configuration  more  or  of  several  order high  termed  riffles  whereas  mostly  scouring as  can  information Regression sophisticated techniques  times  at  these  records  Platts,  to  the  distinguish  (Richards, bedform have  criteria  been  1976a  advocated  are  are  also  features,  i.e  the  fundamental  unit  morphological, Jones,  1986)  et have  Milne, (O'Neill in  experience  1982  as  well  ; as  significance.  between  differencing  are  bars  and  order  al, been  simplest  ,  width.  nature  bears  1986)  bed,  discharge  single  (Leopold  1955) provide  a  the  which  storage  Thompson,  sedimentological (Wolman,  bed  (Church  ;  of  channel  formative  which  1983  and  the  three as  gravel-bed  aggradational  channels,  sedimentological  (Beschta  the  of  some  considered  Werrity,  undulations  mostly  some  be  and  Although  elevation  rivers  low-mobility,  regular  organization  and  hydrodynamic  mobility  in  portions  actuality,  hydrodynamical  biological  of  low  In  channel  Ferguson  less  conditions  In  bar-pool-riffle, of  areas  pools.  present.  low  bed  Topographically  known  in  considerations  ubiquitous  rivers in  configurations  and pools  1982a) and to  1964)  and  invoked,  bed  most and or  natural riffles.  the  more  Abrahams,  1984)  discriminate  between  pools  and  riffles  However,  these  simplification. variety  a  record  of  procedures In  of  the  from  inevitably  reality,  tridimensional  hydrodynamic  longitudinal  pools  and  transport  elevations.  introduce  and  morphological  bed  riffles  display  expressions  conditions  some a  related  of  any  to given  s i t u a t i o n . Bed  elevation  spacing  of  the  scale  constrains  emphasized  ;  average an  Milne, 5  isometric  7  of  valid  even  However,  irregularities  exist.  Some  Keller  the  case  of  have  Keller,  1982),  and  ;  Melhorn, on  studies  of  or  1972,  being  These  sequences  significant  pool-to-pool  ;  range  the  authors  ;  width.  wide  the  suggest  scales  of  this  with  channel  width,  bedrock  channels  (Keller  location of  the  ability  appear  the  scatter  that  some  floodplain  pool  units  of  obvious  1982a).  effects  would  a  any  1964  Jones,  channel  reveals  (Milne,  Possible  issue  for  of  on  stream  al,  and  over  consideration  effect  pool-riffle  the  if  study  1978).  inhomogeneity  and  Church  to  mean  1976b  pool-riffle  relationship do  see  of  et  1976a,  consistency  Melhorn,  spacing  ;  times  scaling  apparently  isometric  Richards,  useful  Several  consistency (Leopold  1982a  to  apparent  and  ;  to  behaviour.  relative spacing  nevertheless  sequence  their  the  1975  1978  are  pool-riffle  riffle-to-riffle Harvey,  series  to  have to  The  but  be  other  local  latter  (Gallinattij  of  addressed  particularly  controls are  the  planform  a  determining  ;  Lisle,  boundary via  1986). materials  transport yet.  susceptible  on  and have  them  proposed  controls  1984  characteristics  been  these  materials  arrange  not  of  to  into  The  latter  be  studied  in  controlled In  some  accounted  or  the  its  (Keller  additional  channel more  fundamental  the  gravel-bed  rivers.  of  on  the  bar  or  sometimes  resulted al,  1971  1980,1983,1984 the  first  alternate  bars  do  sequences  on  However, pool-riffle  alluvial pool-riffle  river  a  stream  development such  creation  length,  Thompson  distance  of  10  river  ;  S. I k e d a , .  stage bear  is  yet  to  and  unclear and  channels.  sequence  of some  sequence  Some be  which  many  times  albeit  straight  not  meander  in  with  the  straight  alternating  bars  1973,  ; to  Moreover, pool-riffle  grounds.  is  the  meandering  for  1983  appear  field  what  authors  to  also  would  hydrodynamical  prerequisite  bank  development.  analogies  field  have  H.Ikeda,  these  been  all  one  even  of  rather  often  channels  ;  a  bed  rapprochement  from  pattern,  1984):  these  has  This  alternate  1974  of  represents  development  Sukegawa,  morphological it  in  the  origin  enigma.  meandering  studies  ;  .the This  in  locations  the  in  represent  the  Jones,  as  For  a  morphology  that  pool  Laboratory  of  initiation  fact  imitating  et  fluvial  meander  channels.  Jaeggi,  and  meander  1982a).  threshold  consists  the  other,  (Chang  of  along  issue  problem  with  situations,  inter-riffle  basic  in  based  occur  large-scale  (Church addition  be  width.  undulations  linked  an  Milne,  can  different  process  ;  to  of  bedform  the  1973  bedforms  proposed  A  in  variability  controls  before  channels.  spacing  coexistence  lag  Melhorn,  laboratory  watershed  sinuosity  and  the  scaled perhaps  the from  by  increases  is  by  arising  1982)  (1986)  properly  situations,'  for  bedforms  of  and  actual  who  link  between  phenomenon consider  meander  in the  development  142  have  accordingly  proposed  development  (e.g.  1986).  rapprochement  The  phenomena  are  consistency  in  and the  material that  the  do  distance  circumstances.  currents  In  may  coincide  the  Meandering for  which  perturbing  factor  Bedform  1973),  appears  each  of  classification  bed  indicates alluvial occurs  microstreams  et  ice, al, a  triggered  ocean ;  Zeller,  flow-induced by  situations  over  in  1964  represent  and  However,  phenomenon  (Leopold  these  wavelength  particular  i.e.  be  relative  proper  under  glacier  may  two  fine-grained  in  to  development  the  sequence only  these  scales.  with  meandering  atmosphere  for  of  river  Thompson,  meander  range  conditions,  thus  by  half  channels  ;  between  justified  wide  alluvial  1976  link  between  the  of  Lewin,  pool-riffle  (Goricky,  in  phenomenon  A. 2  a  addition,  plates  ; causal  a  hydrodynamic  and  1967).  show  models  further  over  phenomena  hydrophobic  and  meandering  not  varied  1972  proportion  that  both  under  Keller,  apparently  interriffle fact  conceptual  a  distinct  (Parker,  conditions  of  1976).  pool-riffle  o c c u r r e n c e  Bedforms particular and  in  are  display  generated a  characteristics Attempts  to  configurations Indeed (e.g.  the Simons  general by  wide  variety  of  the  unify of  and  the  shearing of  pool-riffle flow  shape  and  environment  in  in  various  dominant  and  a  unique  scales  flow-regime  Richardson,  1961  are  over  a  size  related  granular  which  rare  in  Southard,  to  they  conceptual  classifications ;  sequence  of 1971)  bed the grow.  model the  in  bed  literature. bedforms do  not  cover  the  being  wide  mostly  proposed  range  based  a  on  unifying  arguments  pionered  merit  apparently  of  established  bed  are  which of  juxtaposed  provided  by  H.lkeda's  The  limits  configuration  can  parameters.  Some  for  various  gradient 1982; take  into  from  fully bar  Romashin,  under  the a  given  unlikely attempts rough  energy to  by  the  subcritical  forms  to  (described  in  section  alternate  bars  (of  dunes 2.5.2). sand-bed  flows is  to  terms  of  have the  governed Pool-riffle laboratory  and  offered on  and  an  bedform  macroforms  of  describe  requirements  the  stream  energy  and  Jones,-  descriptions  do  not  bed  material  to  a  relative  manner  in  tend  to  the  be  Preliminary suggest  succession by  bed  hydrodynamic  Church  the  field  some  of ;  and  generalizable.  writer  of  pool-riffle  type  via  gradient  be  groups  also  each  those  characteristics  and  of  meso  of  1970  However,  cases)  experimental  tried in  (not  features.  described  develop  1985).  account  are  to  and  Florsheim,  classification in  have  processes  based  for  occurrence  authors  types  (1983)  domains  be  the  three  realm  (1973,1975)  of  has  mesoforms  classification  presumably  (Kopaliani  entrained and  bar  the  large-scale  Evidences  results.  recognized  Leeder  bedform integrated  some  (1975)  conceptual  model  microforms,  bars.  on  fluid-dynamic  are  systems,  Jackson  This  in  Jackson  which  channel  genetic  mechanics  on  namely  natural  based  literature.  based  latter  and  apparently  bedforms  Russian  parameters.  in  experiments.  well-formulated  the  sequences  of  being  met  flume  model  configurations,  macroforms,  conditions  sand  in  or  spatio-temporal  of  of  bedforms  mobility  sequences experiments)  that  as  number well  occur  as when  the  mobility  appear  number  at  their  long  for  also  appears  to  a  and  of  an  effect  be  amount  an  East  of  the  Dune  grain  function  of  in  beds  size,  the  European  an  and  mobility  has  is  expected  mobility  hence  in  the  to  been  literature  has  transport  and  component  this  in  sediment  transit,  actually  Russian  although  increase  morphological  and  number  in  the  rivers  morphology  bar  3).  given  variety  mobility  in  a  mountain  increase  material  importance  wide  instance,  to  of  the  below  1979b).  in  pool-riffle  For  related  a  Increasing  on  documented.  of  in  1983).  be  Karahan,  bedforms  recognized  (Gergov,  generally  stresses  existence  expressions  (i.e.  relative  (Yalin  The  low  higher  shape  parameter  is  to  have  not  been  number  can  or  the  in  a  fundamental  greater pool-riffle  unit. The the  mobility  migration  experiments are  -;  variable is  of and  sometimes  1983  stability Miwa,  the  hydrodynamical further  pool-riffle  (H.Ikeda,  bed  to  particles. originate  j  Lisle,  to  the  1986)  factors  in  in  Ferguson  most  excess  influence  rivers  and  Werrity,  which  is  rivers,  available  which  promote  riffle  planform  control  (Kinoshita  or  from  (Church  and  Jones,  mobility  is  discover  below,  bar  addition,  it  interesting  or  sedimentological 1982). likely  very  gravel-bed  stress  As related  on  laboratory  sinousity  migration,  nil low  low  ;  of  Factors from  some bars  of  1975  speed  small  also  Alternate  sequences  The  related  has  sequence.  1985).  either 1974  the  relatively  undoubtly  entrain  magnitude  migrating  Jaeggi, £ut  number  we to  to bar and and shall bar  shape. In  is  to  note  that  some  criteria  •for  alternate  also  included  between  to  experiments sequence  of  the  the  use  occurrence.  be  The  which  to  pool-riffle  sequences  local  mobility  flow  and  riffle  of  Chang,  cause  1984)  and  related the  1985)  of  to latter  in  for  some  pool-riffle  the  spacing)  1984)  confusion  and  reasons  results S.lkeda  on (1984)  is  pool  and  and  than  riffle  in  is  channels  1.0  are plan  if  (i.e.  1974).  vortices, the  the  In  case  whether  mostly  above  of  or  not  1.0,  pool  determined  (Gallinatti,  flow  so-called  the  or  in  obstruction  even  below  would  scale  sequences,  number  flow  large  develop  Miwa,  geometry  in  streamside  creating  smaller  mobility  the  or  and  occurrence  However,  possibly  Kinoshita  location to  channels  pool-riffle  flow,  number  average  intersection  former  criteria  conditions.  can  controlled  the  (the  these  irregularities  the  planform  some 1983,  ref.  and  for  threshold  intersect  bars  (height  limit  planform  average  channel,  Jaeggi,  Jaeggi,  laboratory  of  ;  sceptically.  lower  correspond  ;  same  geometry  received  The  forced  some  1974  However,  difficulties  in  width  bar  1961  regime  impede  laboratory to  or  fixed  number.  (Shen,  conditions  the  (Sukegawa,  mobility  types  scaling  flow  occurrence  the  bar  possible the  bar  by  1984  ;  the Lisle,  1986). Classifications alluvial  milieus  confusing 1978).  morphological the  are  array The  of  of  latter diversity  large-scale  bar-pool-riffle  primarily  based  terms  concerning  situation and  bedform  on  is the  aspect  likely lack in  sequences bar  form.  bar  classification  a of  in  a  fully  There  is  (Smith,  consequence  of  global  approach  full-scale  rivers.  a  their to Riffle  planform  may  (e.g.  Richards,  (e.g.  and  occur  represent  be  the  bar  the  and  This  Jaeggi, and  and  Jones  morphology  which  number; channel  edge.  transverse  Church bar  mobility  fills  leading  the  shape  conditions  formation.) and  bar  bar  (WhittaKer  riffle  the  medial  at  and  greater the  proposal  riffle  remains  to  verified. and  alluvial  the  sediment  storage  paper,  P.  theirs  which  channels.  hence  not  partly  either  be  pool-riffle in  the  The bedforms of  for  on  hydrodynamic  case  pool  (e.g. of of  is  desirable  reference  a  which  complete  will  and  of  and  the  the latter  similar remnants,  of  remain  for  to a  multithread  descriptive  and  classification  Platts,  (e.g.  eliminate  to the  1986)  Baker,  classification  order  can  obstruction-controlled  and  canyons  in  riffles  case  to  distinguishes  scheme  macroform type  bedrock,  addition  quantities.  Beschta  emergence highly  the  however  milieus,  on  sequences  discussion  complexes  attempts  based  the  bar  relevant  alluvial  of  classification  These  based  classification  In  function In  a  includes  a  classification  bars.  proposes  particularly  rivers  this  of  attempted  macroforms.  resistance  role  also  also  channels  primarily  Ashmore  refinement  (1982)  criteria,  between  In  Jones  gravel-bed  morphological  frame  its  that  hydrodynamic  in  component  merely  (Note  bed  gradation  with  alternate  streams  of  to  or  1983).  different  related  Church for  a  sometimes  diagonal  mountain  domain  described  represents  type  of  another  mobility,  to  under  possibly  transverse,  Werrity,  systems  1982)  (1982)  from  1976b),  Ferguson  step-pool  is  vary  or  bar  1984). for  provide  large-scale a  confusions  universal due  to  unregulated  A.3  nomenclature  Flow  processes.  in  the  literature.  origin  and  evolution  of  the  pool-riffle  p h e n o m e n o n  Studies formative a  Therein  only  over  acting  riffle.  the  However,  velocities  to  discharge  and  velocity for  in  tractive  cm  from  the  showed  sorting  reversal  in  1979  Hirsch  and  the  over A  systematically data  has  a  large  local  of  bottom force  than  in  the  bottom  at  (i.e. riffle)  bottom  may  in  the  medium  the  reversal  occur  terms  of  measured  while  his  set  1969),  taken  at  1.5  over  the  (Keller, D50  pool  tractive  riffle  the  a  the  for  reversal  that  in  riffle  tendency  a  discharges  found  the  (1971).  about  32  mm  variability  and  possibly  the  apparent  effects. some  surface  coarser  ;  (which  over  discharges.  never  particle  of  general  exceeding  rather  Nevertheless  that  Keller  medium  the  at  performed  respectively  to  pool  by  to  proportional  the  velocity  bed  low  Keller  a  formative  was  reported  discharges,  larger  units  measurements  for  noted in  pool  bottom  individual  be  hypothesized  force  original  riffle),  equalize  highest,  of  to  Keller  the  the  low  assumed  bed)  pool-riffle  cross-sections,  For  he  were  velocities two  in  Velocity  sequence  along  (which  on  pool.  rare.  near-bed  a  velocities  processes  are  selected  measured  and  flow  flows  through  were  of  than  flow and  authors bed  that  have  material, of  adjacent  competence  between  Abrahams,  1981).  argued  that  riffle  material  pool, pools Andrews  could  being  result  and (1979)  riffles  in  from  a  (Lisle,  reported  a  148  reversal  of  the  pool-riffle same at  mean  stream.  river high  a  bottom  A  stream  on  quantity  bed  and  weaknesses  regarding  Only  velocity  shear  stresses  could  clarify The  authors  the  bar  significant  The  most  that  it  1971,  appealing  of  reversal  a  lateral  sorting  aspect  of  through  for  the  pool-riffle  latter from  estimated. allow  the  issue.  refuted  Demissie,  the  channel  the  by  some Milne  pool  was  pool  reversal  of  1982).  between  from  to  albeit  (Lisle,  and  generally riffle.  hypothesis  maintenance  bed  sequence  reversal  been  sequence  of  tractive  importance  sorting  small  suffers  would  sinuous  the  a  the  which  also and  longitudinal  account the  has  relatively  of  actually  stress  Bhowmik  that in  shear  2.16)  was  sedimentological  ;  than  can  initiation  remainsnot  1979  ;  the Keller,  1983). The  problem  initiation to  flow  study  physical  of due  structure  explanation  are  out  stress  (equation  the  however  estimated  or  or  1972  pointed  properly  stress  (Teleki,  the  the  hypothesis  reversal  measurements  velocity  shear  adjacent  more  and  the  or  (1982b)  profile be  a  approach way  the  a  for  in  estimated  that  river,  -  (1987)  support also  concluded  stress  Petit  to  Fork  reported  shear by  Petit  the  occurrence  velocity  not  East  actually  study  His  to  the  average  recent  occurred.  local  of  reversal.  the  for  (1979)  seemed  velocity  force  Lisle  reversal  flows.  pebble-bed  velocities  have  to at  pool-riffle  natural  have  pool-riffle  sequences  offered  collected. are  is  between  discharge.  been  been  sequence  feedback  formative  nevertheless  observations  possible;  the  viewed  bed  Several but Two as  a  difficult morphology  attempts no  systematic  alternate either  at  views a  flow  or  sediment On  the  pool-riffle of  transport  phenomenon.  one  Langbein  hand,  sequence  the  moving  waves.  initiation  bedload  Thompson  effectively Schick  be  (1983)  fact  confined  that  downstream that  a  from  wave  pool-riffle  of  pool-riffle Milligan  sequences  et  al,  bedforms  1980).  would  In  be  taken  character.  some  distance  an  indication  as  an  be  responsible  for  been  Campbell  and  to  which  noted  is  in  Sidle,  creation  the  a  represent  has  prerequisite  over  transport  the  and  could  could  case,  may  Lekach  pulse-like  (which  this  kinematic  transport  was  rivers  (e.g.  as  spacing  developed  Wavelike  gravel-bed  property  mechanism.  sequence  that  some  travel  a  phenomenon)  initiation.  characteristic  a  had  transport  transfer  by  bedload  reach  proposed  pool-riffle  such  bed  canyon  (1968)  would  that  that  pool-riffle  sediment  which  of  river  the  kinematic  inherent  control  Leopold determined  argued  observed  non-undulating The  was  materials  (1986)  under  and  other 1985  of  ;  organized  organization  of  flow  patterns. On  the  velocity  other  or  proposed. principles were other but by  could  Some  authors  periodic  Thompson probabilistic  1971  valid  authors  Keller  several  stress  (Yang,  not  hand,  and  establish  ;  arguments  the  also  to  in  (1973),  Richards to  flow  1973)  patterns  have  but  for  pools Ferguson  apparent  the  and  their  contrast, of  as  Werrity  periodic  been  arguments  In  origin  adapted  of  minimization  riffles,  and  also  to  conditions.  (1976a) the  how  appealed  account  structure  (1986).  about  channel-forming  attempted  Melhorn  in  Cherkauer,  under  flow  ideas  distinct described  (1983)  Yalin's  and  (1971b)  occurrence  of  zones  of  relatively  longitudinal Shen  direction.  (1964)  nature  turbulence  produced  sophisticated  using  instability  However,  none  For  through in at and  of  the  the  the  water  formation  the  of  a  of The  obstruction  been  a in  an and  helical upward  flow the  of  will  reach.  Scour  persists  which  and  turbulent  diffusion  lobate  deposition  area  the  which  advection  gradually  bank.  resembles  on  some  promote an  pressure  bank.  This gradient results  downward The  the  appears  of  Near  high  directed  depend  for  (1984).  obstruction,  inner  structure  circulation  the  the  albeit  pressure  structure  near  the  deposition.  opposite  adverse  flow  for  well-tested.  Gallinatti  the  face  (1976),  qualitative  near  the  A  obstruction-controlled  is  at  wall  transport  and  generates  depth  during  scour have  an  of  Parker  flow  with  alternating  mechanism.  impinging lower  and  sediment  streamside  proposed  Einstein  necessary  of  ideas  combined  this  were  zones  is  of  obstruction  extent  helicity  the  decay  by  that  development,  pressure  and  treatment  in  of  generating  suggested  of  the  gradient,  obstruction.  core  case  earlier,  growth  distinct  foregoing  stresses  circulation  vorticity  not  treatment  configuration  the  and  . the  obstruction  pressure  a  sequence  theoretical  whereas  by  decade  the  alternating  the  pool-riffle  from  but of  a  lower  secondary  analysis,  friction  development  an  that  originate  more  and  Nearly  proposed  could  and  higher  shape  particular  along  the  distance the  high  the alternate  after velocity  creation bar.  of  151  A.4  Pool-riffle  The  sequences  mechanisms  incipient  meandering  universal  quantities this  The  to  involved  do  processes  this  prospects  pool-riffle  maintenance  not in  instrumental  the  are  indeed  spatially  two-phase  or  produce  involved  sequence  measure,  in  follow  and  alluvial  pool-riffle  difficult  situation  or  physical  the  being  for  development  of  extraordinarily  perspectives  proposed  agreement.  development  :  distributed  phenomenon.  and  data  From  resolution  constraints. In  this  many  simpler  introduced the  in  this  above  classification, study  the  now.  reflexion  A  problem  information  lead  under  controlled  conditions influential as  several  would  is  phenomenon  by  to  ignore the  the  laboratory  hydrodynamic  widely and  detailed  hydrodynamic  crucial  issues.  at  addressing of  need  for of  the  measurements  begin  to  to some  fundamental  work  done  knowledge  until  on  and  combinations  Some of  of  working working of  parameters order  the  detailed  Such  in  for  problems  possibility  sedimentological  like  criteria  extensive  conditions, varying  behaviour  the  the of  that  equilibrium.  necessary  level  note  understood,  the  about  most  actual  consideration  allow  well  morphology,  it  and  yet  those  to  sequence  hydrodynamics  that  about  to  not  notably  perhaps  pool-riffle  are  their  illustrate  interesting  pool-riffle  varying  remarks,  hence  well  their  pool-riffle  also  of  and  questions,  is  chapter  on  occurrence the  it  aspects  controls  their of  perspective,  to  some as explore  The be  made  priori can  writer under  that be  the  such  the  theory  be  transferred  statement  represents fundamental  introduced the  describes  the  a  design. first,  research  rapid  scientific  conditions.  processes  reproduced  to  research  that  working  physical  appropriately  to  current  believes  in field  acting at  necessary regarding  a  chapter  that  2,  the  sense, on bed  is  in  full-scale  could  demonstrated  laboratory  rationale  according results  The  can latter  behind  the  current  the  way  morphology  the project  to in  a  systems  scale,  scepticism.  and  step  it  smaller  without  motivation In  If  progress  truly  rivers.  

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