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Hydrologic controls of land sliding in Tsitika Basin, Vancouver Island

University of British Columbia

Landslides are common occurrences in steep mountainous terrain of the Pacific Northwest. Many resource industry activities occur in locations and at times when there is potential for instability to occur. Limiting the exposure of workers during periods of high risk is seen as one way of minimizing worker fatalities. In order to minimize the exposure of workers it is necessary to understand the linkages between rainfall epsiodes, groundwater fluctuations, and landslide events. An intensive groundwater and precipitation study was conducted in Russell Creek basin within the Tsitika River basin on Vancouver Island. This basin is the site of a Ministry of Forests study examining fine sediment contributions from logging and natural sediment sources. The results of this study show that slope instability can result from either high intensity rainfall or rain-on-snow meltwater production. Instability associated with high intensity rainfall occurs in rainstorms with approximately a two-year return period. Instability associated with rain-on-snow meltwater production can be associated with storms with return periods of less than a year. Thresholds for instability need to be refined to allow for the development of an effective shutdown system for forest harvesting operations. Measurement of groundwater response during storm events showed that there is rapid response of the groundwater system to precipitation inputs. Under high intensity rainfall, the response may be considered almost instantaneous. Modeling of the groundwater responses based on observed groundwater records showed that it is possible to closely model the response of the groundwater system. The key use of calibrated models for groundwater response is their ability to correctly predict the timing of groundwater peaks rather than estimation of the exact magnitude of the response.

Thesis/Dissertation

application/pdf

2009-05-22

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http://hdl.handle.net/2429/8058

Geography

University of British Columbia

UBCV

DSpace