Anticipating Glacier Lake Outburst Floods (GLOFs): an impact-based forecasting framework for managing GLOF risks in Nepal.

Sammanfattning: Glacier lake outburst floods (GLOFs) are an increasingly documented threat across the Himalayan region, wherein Nepal is situated. GLOFs involve a rapid discharge of water from a lake situated at the side, front, within, beneath, or on the surface of a glacier. Forecasting the impacts associated with such events could facilitate the development of proactive risk management approaches. Impact-based forecasting (IbF) and anticipatory action (AA) are proactive strategies which are of emerging interest among humanitarian actors and disaster risk management authorities both in Nepal and globally. To assess what a proactive approach could look like for addressing GLOF risks in Nepal, this thesis takes inspiration from existing GLOF risk models and applications of anticipatory risk management approaches for other hazard types. The research questions addressed are as follows: 1. How are glacier lake outburst flood risks to Nepalese communities presented in academic literature? 2. How could impact-based forecasting address glacier lake outburst flood risks in Nepal? A systematic literature review of potentially dangerous glacier lake (PDGL) risk models enabled the assessment of existing capacities to anticipate GLOF threats. The research also collates insights from experiences in applications of IbF through six semi-structured interviews and a non-systematic content analysis of IbF and AA documents. Both research components ultimately inform a framework showing how GLOF risks could be addressed through IbF. Part 1 of the thesis looks at the state of risk data for GLOFs in Nepal, presenting an overview of PDGLs and associated outburst models. The findings show that of the 47 classified PDGLs posing a risk to Nepal, only four are assessed to have outburst models quantifying projected impacts using physically-based hydrodynamic models. Although, there is high uncertainty and discrepancies in projected inundation zones and lead times across studies for all assessed lakes. Most studies additionally do not assess household-level vulnerabilities, serving as a key knowledge gap in capacities to anticipate impacts in a way that is meaningful for holistically risk-informed activities. Part 2 discusses the results of the study around the proposed framework, showing how GLOF threats in Nepal could be addressed through IbF. First, capacities to predict GLOF events are discussed under two categories, the longer-term readiness triggers, and shorter-term activation triggers. The GLOF risk assessments studied model an array of trigger and outburst mechanisms that could theoretically be observed at each PDGL to assess the likelihood of imminent outburst and aligned with anticipated outburst scenarios. Some examples of assessed triggers include mass movements, high temperatures or precipitation, and earthquakes. A discussion of the lead times available for implementing risk-mitigating early actions upon recognition of these triggers follows this. Next the two overarching phases of the framework, the readiness phase, and the activation phase, are expanded upon, discussing the proposed activities within each. The readiness phase involves the long-term anticipation of GLOF-related impacts to enable the implementation of risk-informed preparedness activities. The overarching stages of this phase include identifying PDGLs, developing impact-based forecasts, and developing early action protocols. A related theme drawn from the interview respondents regards the importance of IbF-informed preparedness activities such as developing community capacities to operationalise forecasts and implement early actions. The activation phase is the period for refining IbF scenarios and implementing predefined early actions. An issue emerging from the interviews was that of working with dynamic risk data in anticipatory action. It is suggested this could be mitigated in the GLOF context by enabling scenarios and associated protocols to be refined according to emerging risk information. This thesis ultimately provides an assessment of the risk data associated with GLOFs in Nepal and proposes an IbF framework to address these risks, within the realms of assessed forecasting capacities. By leveraging IbF and AA approaches, supported with investments in hazard modelling, the proposed framework could enable timely risk-reducing actions in the face of anticipated GLOF threats.