Modelling and evaluating GLOF risk management measures in the Kyrgyz Ala-Archa valley

Glacier lake outburst floods (GLOF) are mass flow hazards of severe destructive potential and far reach that can cause extensive damage to the natural and built environment posing a threat to people and their livelihoods. Diverse risk management measures have been proposed and been implemented in order to reduce the risks associated with GLOFs. However, systematic studies on the effectiveness and cost-benefit of such measures in the contest of disaster risk management (DRM) are largely lacking.Here we model, map and evaluate GLOF risk measures and analyse how the implementation of different GLOF DRM measures alters GLOF risk. We compare cost and benefit of five potential measures in the mountainous Ala-Archa catchment in the Kyrgyz range south of Bishkek, the capital of the Kyrgyz Republic. Using the RAMMS debris flow software, the extent of two GLOF scenarios are modelled for the situations of (i) no DRM measure (current state), (ii) lake volume reduction, (iii) a deflection dam, (iv) a retention dam and reservoir, (v) an Early Warning System, and (vi) land use planning.We analyse the effect of the different DRM measures by examining the three components of risk, namely hazard, exposure and vulnerability. We estimate the expected cost of the respective DRM measures and compare it to the costs of the potential damage caused by the GLOF scenarios. While we assess hazard and exposure quantitatively, we analyse vulnerability in a qualitative way, based on socio-economic characteristics such as age, gender, education, economic diversity and dependency.With increasing numbers of glacier lakes and potential disastrous lake outbursts linked to climate change, often combined with increasing exposure of infrastructure and human assets, cost effective GLOF DRM is of growing importance.  While the absolute numbers based on the exposed assets, cost and damage will differ for other settings, the conceptual approach of this case study can be applied to other mountainous catchments. This study’s main findings serve as a basis for decision making in similar settings with stakeholders aiming for cost-effective GLOF risk management.