Computer program for stability analysis of steep, cohesive riverbanks

The ability to predict the stability of eroding riverbanks is a prerequisit e for modelling alluvial channel width adjustment and a requirement for pre dicting bank erosion rates and sediment yield associated with bank erosion. Mass-wasting of bank materials under gravity occurs through a variety of s pecific mechanisms, with a separate analysis required for each type of fail ure. This paper presents a computer program for the analysis of the stabili ty of steep, cohesive riverbanks with respect to planar-type failures. Plan ar-type failures are common along stream channels destabilized by severe be d degradation. Existing stability analyses for planar-type failures have a number of limitations that affect their physical basis and predictive abili ty. The computer program presented here is based on an analysis developed b y Darby and Thorne. The software takes account of the geotechnical characte ristics of the bank materials, the shape of the bank profile, and the relat ive elevations of the groundwater and surface water to estimate stability w ith respect to mass failure along a planar-type failure surface. Results ca n be displayed either in terms of a factor of safety (ratio of resisting to driving forces), or probability of failure. The computer analysis is able to determine the relative amounts of bed degradation and bank-toe erosion r equired to destabilize an initially stable bank. Data for the analysis are supplied in the form of either HEC-2 hydrographic survey data files or user -supplied bank profile data, in conjunction with user-supplied geotechnical parameter values. Some examples, using data from the Upper Missouri River in Montana, are used to demonstrate potential applications of the software. Copyright (C) 2000 John Wiley & Sons, Ltd.