In the Kingdom of Bhutan growing glacial lakes pose a known threat of Glacial Lake Outburst Floods (GLOFs) that pose a risk to remote communities and large urban areas (Carrivick and Tweed, 206). Most of these lakes are surrounded by extremely steep, high slopes that meet the conditions for large landslides failure, and, rock avalanches are known from other parts of the Kingdom (Dunning et al. 2006).
Hazard cascades that originate from the failure of slopes above glaciers and glacial lakes pose a significant, and, debatably, an increasing risk to life and infrastructure. The Nov. 2020 Elliot Creek, Feb. 2021 Chamoli (Shugar et al. 2021), and, March 2021 Sendongpu hazard cascades all originated as ice:rock avalanches on high, remote mountains where a ‘normal’ runout would have caused few issues, but, displacement waves from glacial lakes; transformation into mobile debris flow/floods; temporary landslide dams, and, large-scale sediment transport greatly extended their risk footprints, with potential for long-term impacts. In all instances it is the presence of water that allows the initial solid dominated landslide to become a far more mobile flow/flood, this can be from the rapid melting of glacial ice during landslide motion, or, from a glacial lake.
In recent years there has been rapid development in our ability to detect slopes that pose threats, and, in modelling landslide and flood inundation either as separate components of a hazard cascade, or, all within one modelling environment (Frey et al. 2018; Mergili et al. 2020) . In many instances the modelling of a hazard cascade is responsive, a back analysis to yield better understanding of an event. In these cases, we often have validation data we expect our models to fit. However, if we want to help Governments and agencies tasked with disaster risk reduction before an event, it is far more challenging (Marlovits et al. 2021).
Here we aim to use ensemble modelling approaches using cutting edge codes (RAMMS; a.avaflow) to characterise down valley inundation and arrival times from landslides and their resultant hazard cascades in the Kingdom of Bhutan. We will then use this information to quantitatively specify the most beneficial locations of early warning systems (EWS) and sensors to provide life information on the nature of the threat.