Glacial lake outburst floods in the Pamir of Tajikistan: Challenges in prediction and modelling

Abstract

Glacial lake outburst floods (GLOFs) are potentially highly dangerous events and have contributed to numerous disasters in history. Today, computer models are standard tools to estimate the magnitude of hazardous events in the future and to support risk mitigation. The present paper explores the potentials and limitations of modelling for predicting the motion of potential future GLOF events, based on examples from the Pamir (Tajikistan). Since the flow behaviour of GLOFs is in between debris flows and floods, different model approaches come into consideration, though none of them is perfectly suitable for GLOFs. RAMMS as a mass movement model and FLO-2D as a river hydraulics model were employed comparatively for the same areas. The friction parameters for RAMMS and rheologic parameters for FLO-2D were first calibrated by back calculation with the well-documented Dasht event from summer 2002, and then applied to other areas. However, the applicability of such parameters to GLOFs of different volume and over a different topography remains questionable. The results may nevertheless be a valuable input for risk mitigation efforts, but due to the complex nature of GLOFs and the connected uncertainties, particular care is required when interpreting the model results. The critical points and potential approaches to deal with the limitations are discussed in the paper.