UBC Theses and Dissertations
Hydrologic behavior of a forested mountain slope in coastal British Columbia Tischer, Evelyn
This is a study of the hydrologic behavior of a forested west coast mountain slope soil. Flow mechanisms were investigated using experimental results, mainly outflow hydrographs, and a simple model of saturated flow over a steep bed, described in the second chapter and called the kinematic wave model. The main experiments consisted of subjecting the forest plot to both concentrated and uniform irrigation. The rationale for using concentrated irrigation was that it was expected it would enhance flow in low resistance paths or as fingers in the unsaturated zone, also called short-circuiting. It was concluded that the soil-water system behaves as if short-circuiting were not enhanced by concentration of irrigation. The fact that both the observed hydrograph and the kinematic wave model hydrograph display a straight line rise was the rationale for using the kinematic wave model. It indicates that the system behaves as if the kinematic wave model were valid. Readily verified assumptions are a steep bed slope and a high hydraulic conductivity due to concentration of low resistance paths on top of the bed. As for other assumptions, it can only be said that the system behaves as if they were satisfied. In particular it behaves as if no short-circuiting occurred. Using the kinematic wave model, an effective hydraulic conductivity of 1.6 x 10⁻⁴ to 3.2 x 10⁻⁴ ms⁻¹ was obtained for the saturated zone. Finally, it was shown that nonlinear flow, if it occurs at all, is probably uncommon in the unsaturated zone of the Forest plot and its vicinity. It is not certain whether it can occur in the saturated zone of the Forest plot.
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