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Forest groundwater hydrology: implications for terrain stability in coastal British Columbia

University of British Columbia

The groundwater regimes of two coastal British Columbia field sites in landslide prone terrain have been assessed. The first site involved instrumentation of a landslide headscarp area with tensiometers and piezometers to characterize the groundwater regime over one year. Piezometers were designed and manufactured specifically for use in this project. Data collected from the study site indicate a highly variable distribution of storm-induced positive pore pressures across a small area. Field observations combined with data analysis suggest that macropore flow is responsible for the pore pressure distribution and rapid drainage. The second site involved analysis of piezometric and precipitation records from the Carnation Creek Experimental Watershed. Analysis of records spanning almost 8-years revealed a number of observations of temporal and spatial distributions of groundwater behavior that deviate from simple hydrologic models. The study area is characterized by frequent occurrence, and a complex spatial distribution of high groundwater levels. Most piezometric sites displayed a 'capped' groundwater level that is rarely exceeded with increasing precipitation. Analysis of records also showed that forest harvesting could cause an increase in the response of soil water to precipitation. An increase was manifested in some, but not all of the chosen study piezometers that were within the harvested area, suggesting that the impacts of harvesting on groundwater may be site-specific. A model of groundwater hydrology that parameterizes the effect of topography on the distribution of watershed groundwater levels was assessed for its ability to predict observed piezometric recordings from a small coastal watershed. The hydrologic model is a component of a terrain stability model named SINDEX. Piezometric recordings were available for a number of hillslope positions and aspects. The model was found to have satisfactory predictive capabilities of relative groundwater levels if conservative input parameters are used.

Thesis/Dissertation

application/pdf

2009-05-25

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http://hdl.handle.net/2429/8136

Civil Engineering

University of British Columbia

UBCV

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