An effective non-Newtonian approach in simulating GLOF Floods

Glacial Lake Outburst Floods (GLOFs) often occur at high elevations, resulting in catastrophic flash floods while leaving little or no time for effectively managing them. They are characterized by destructive velocities of several m/s, enabling the transport of a large amount of debris and sediments. Due to a combination of the solid and liquid forces, these flows are characterized by greater momentum and continue recruiting debris and sediments along the path. As a result, they achieve farther run out distances compared to clear water flows. Hence, they deviate largely from pure water mechanics or Newtonian hydraulics. Modelling them using non-Newtonian physics and sediment transport may pave the way for an accurate simulation of these floods. Therefore, in this study, we use various non-Newtonian schemes in a freely available hydraulic model to simulate the recent 2023 Sikkim GLOF flood. We perform Monte Carlo uncertainty-based calibration to estimate the behavioural parametric values for different non-Newtonian approaches in the model. As an outcome of this study, we identify the best-performing non-Newtonian approach and its calibrated parametric ranges. Thus, the study serves as a guideline towards accurate modelling of  GLOFs. The framework adopted in this study can be used elsewhere to simulate GLOFs realistically. As they are expected to become more frequent due to climate change, a pre-assessment modelling strategy for gauging the potential damage can be established for the existing glacial lakes.