UBC Theses and Dissertations
Landscape organization based on application of the process domain concept for a glaciated foothills region McCleary, Richard James
The organization of a glaciated foothills and interior plain landscape was examined by analyzing the spatial distribution of process domains. Glaciations distribute patches of surficial materials with varying hydrologic properties across the landscape and create complex longitudinal profiles. These two factors complicate the use of a traditional method, drainage area – local slope plots, for explaining landscape organization; hence, an empirical approach using logistic regression models was applied. An automated procedure was developed that enabled extrapolation of model results across entire study areas. A 57 km² and a 10,000 km² study area were divided into hydrological response units (HRUs) with an average area of less than 5 km². The HRUs were classified into categories based on topography, hydraulic connectivity, and surface type. A preliminary drainage network was extracted from a LiDAR DEM. The network was sub-divided into reaches, each characterized by a suite of topographic predictors. Ground surveys entailed assigning a process domain class as hillslope, swale, seepage channel, or fluvial channel. Various types of logistic regression models, including mixed-effects, binary, ordinal, and multinomial, were used to predict process domain class. Predictors included longitudinal profile anomalies measured at the reach scale using a normalized stream length-gradient (SL/k) index. The candidate predictors, including SL/k index, soil moisture regime, and mean basin slope, were selected in consideration of groundwater flow systems that operate respectively at the reach, hillslope, and basin scales. Drainage area, the dominant factor controlling domain transitions, was complemented by various predictors, depending on transition and HRU type, including reach slope, and the three groundwater flow related predictors. The study revealed features of a stabilized landscape including an extensive network of swales. Headward channel migration into the swale network is not expected to proceed uniformly across the glaciated landscape; rather, minimal migration is expected where channel heads are anchored below confluences and within over-steepened areas, and higher migration frequencies are forecast in sections of the network that are more evenly graded in terms of both drainage area and slope.
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