A METHOD FOR MODELING WATER TABLES AT DEBRIS AVALANCHE HEADSCARPS

Heavy rainfall during a January 9 and 10, 1983 storm triggered numerous debris avalanches and associated debris torrents in the Smith Creek basin, western Whatcom County, Washington, U.S.A. Rainfall hyetographs and soil parameters are entered in a one-dimensional, vertical, transient, unsaturated finite-difference model to produce vertical soil discharge rates at selected debris avalanche headscarps. The discharge rates are entered in a kinematic wave equation to model water table profiles above the headscarps. Factors controlling hydrologic response to rainfall are assessed. The discharge rates and water tables modeled for the failure-initiating, January 1983 storm are distinguished from those modeled for other severe storms which did not trigger widespread debris avalanches. The modeling technique is suggested as a method of predicting the risk of debris avalanche recurrence. © 1990.