Study on moraine dam failure and resulting flood/debris flow hydrograph due to waves overtopping and erosion

Glacial lake outburst floods (GLOFs) may cause floods of great magnitudes, loss of life, properties and sediment disaster in the downstream river reaches. About 80% of GLOFs (based on 20 cases with known failure mechanisms) were initiated by displacement waves from ice avalanches that collapsed into the lakes from hanging or calving glaciers and rock avalanches. Therefore, an integrated model is essential for the i) prediction of waves generated by ice/rock avalanche, ii) prediction of outflow hydrograph due to waves overtopping and erosion of moraine dam and iii) flow and sediment routing in the downstream for flood risk assessment. Toward development of an integrated model, this study focuses on experimental study of moraine dam failure due to waves overtopping and erosion. Extensive laboratory experiments are carried out by varying size of ice/rock avalanche, shape of the dam, dam material and lake water level. The outflow hydrographs produced by waves overtopping and erosion consist of multiple peaks. For the same falling block and lake water level, the initial peaks are similar for both triangular and trapezoidal dams. However, magnitude and timing of subsequent peaks are different according to dam shapes and dam materials. © 2011 Casa Editrice Università La Sapienza