Original paper

Empirical modelling of outburst flood hydrographs

Herget, Jürgen; Schütte, Felix; Klosterhalfen, Anne

Abstract

Naturally impounded lakes dammed by earth material like moraines and landslide deposits or glacier ice are capable of draining abruptly involving enormous amounts of water by overflow, seepage or drainage through pipes. Such kinds of outburst floods are among the largest floods by magnitude and provide a serious hazard due to their frequently unexpected occurrence. A new model approach based on previously observed outburst flood hydrographs is presented here as previous attempts contain several limitations. Due to numerous influencing factors, physical-based modelling to forecast the magnitude of future outburst floods is hindered by problems of achieving input data for case-studies to model. Black- box models that correlate lake volume with peak discharge of the outburst flood are frequently found to provide a good correlation, but cannot describe unsteady flood components like rise and fall of the water level. Based on an intensive literature review, measured hydrographs of outburst floods from earth and ice-dammed lakes differentiated by drainage processes are compiled. After normalisation to reach a comparable style for the hydrographs of different flood magnitudes and durations, mean values when peak discharge is reached are determined. In combination with regression equations for the peak discharge and flood duration based on drained lake volume, potential hydrographs of future outburst floods can be estimated. So far, the approach is limited by low numbers of measured outburst flood events and missing correspondence of flood duration and drained volume for ice-dammed lakes. This approach could be improved by identification of more specific studies for the deduction of normalised hydrographs and regression equations.

Keywords

flood durationregression equationsglofhydrographnormalisation