Overtopping volume of impulse waves in glacier lakes: Experimental and numerical investigation using rigid dams

Glacier lake outburst floods (GLOFs) that result from the breaching of moraine dams are typical disasters in high mountain regions of the Tibetan Plateau, which endanger vital infrastructures such as the Sichuan-Tibet Railway and Highway. Breaching can be caused by tsunami-type waves, resulting from glaciers calving and falling into impounded lakes, which overtop and destroy their natural boundaries. In this work, we develop an equation for the overtopping volume based on the simplified geometry of fluids running up an incline. Specifically, we propose that overtopping can be viewed in terms of the run-up of solitary waves impacting a structure from which relationships with the dam and wave properties can be established. This equation is tested and verified against physical experiments and numerical simulations of waves overtopping rigid, impermeable triangular structures which serve as idealized natural dams. The proposed equation is found to adequately account for the first-order dependencies of the overtopping volume on the different dam and wave properties. We extend the applicability of this analysis to erodible dams made up of glacier tills, wherein we show the basic dependence of the overtopping volume on the erodibility of the dams and flood scales. • A quantitative relationship between the runup and overtopping volume of solitary waves is newly established. • A novel overtopping equation, developed from geometric arguments, captures its dependence on the wave and dam properties. • An empirical method relating the wave and dam properties to the outburst flood volume is proposed.