Debris-Flow Hazard Assessment and Methods Applied in Engineering Practice

摘要

Debris flows constitute a major natural hazard in mountainous regions. The main elements required for apractical hazard assessment include the following steps: (i) estimation of potential initiation zones andsediment sources, (ii) establishment of a relation between the magnitude and frequency of expected futuredebris-flow events, and (iii) assessment of the flow behavior and delineation of areas potentiallyendangered by flowing debris. A general overview is presented of the main triggering conditions andinitiation mechanisms for debris-flow formation. A brief summary is given of methods to establish amagnitude-frequency relation and to estimate the total volume of sediments transported to the fan duringso-called “design” events. To assess the runout distance of debris flows and potentially affected areas,either simple empirical approaches or more physically based numerical simulation models may be used. Anexample application for a Swiss debris fan illustrates the variability of the results when using three differentdebris-flow simulation models, even though all three models were first calibrated based on the observeddeposition areas of a past event.