the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Feb 2025
Modelling the effectiveness of GLOF DRM measures – a case study from the Ala-Archa valley, Kyrgyz Republic
Abstract. Disaster risk management (DRM) for glacial lake outburst floods (GLOFs) is critical due to the increasing risk posed by GLOFs to downstream communities and infrastructure. However, the effectiveness of DRM measures remains insufficiently understood, which hinders effective and target-oriented decision-making in GLOF DRM. Existing research predominantly focuses on hazard aspects, with few scientific studies modelling the impacts of DRM measures comprehensively. In order to fill this gap, this study assesses the effectiveness of three different DRM measures for GLOFs in the Ala-Archa catchment, Kyrgyz Republic. Using numerical modelling, we map and assess the effect of three DRM measures: lake lowering, a deflection dam, and a retention basin and compare it to the current baseline hazard map. We develop a hazard reduction score for comparison of the measures and evaluate their effectiveness based on cost and benefit considerations. This study proposes a conceptual framework and methodology that can guide the management of GLOF and debris flow risks in similar contexts globally.
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RC1: 'Comment on egusphere-2025-290', Dmitry Petrakov, 18 Mar 2025
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General comments:
The effectiveness of GLOF DRM measures is an important topic worldwide but especially in developing countries with lack of funds for structure protection. Authors used RAMMS simulation to estimate hazard and exposure in combination with cost-benefit analysis to assess the effectiveness of GLOF DRM measures in the Ala-Archa valley, Kyrgyzstan. This valley provides historical records of debris flows caused by glacier lake bursts and other triggers. GLOF risk for downstream areas is significant here considering many tourists in the valley headwaters and some settlements in the risk prone area. Three approaches were considered: annual partial lake drainage, reconstruction of the existing deflection dam at Aksay fan and reconstruction of retention basin in the village of Kashka Suu. All approaches are quite typical for all GLOF risk areas, thus topic of the paper is highly relevant both at local and global scale. The paper provides high-quality case study with significant conclusions. It also provides synthesis of natural and social sciences which is important for cost-benefit assessment of GLOF DRM measures. Novelty of results is quite clear.
Structure of the paper is reasonable, Introduction is well-written, motivation and aim of the paper are fully clear. Authors provide brief description of Teztor and Aksay lake complexes.
GLOF hazard is assessed through mass flow simulations using RAMMS software for different GLOF scenarios under the presence and absence of different GLOF DRM measures. The cost-benefit relationship for the three measures is assessed in monetary terms. Authors provide detail physical description for these measures: annual partial lake drainage, reconstruction of the existing deflection dam at Aksay fan and reconstruction of retention basin in the village of Kashka Suu as well as required funds for their realization. Input parameters for RAMMS simulations looks reasonable, hazard and exposure assessments as well as cost-benefit evaluations are based on state-of-the-art techniques and data, including data obtained from local surveys, field visits and satellite imagery. Lake drainage provides the best benefit to cost ratio for the whole area whereas retention dam mitigates threat for the downstream settlements and deflection dam – for Aksay fan. Discussion is well organized and includes all necessary topics, like hazard&exposure reduction, vulnerability and cost discussions, DRM strategy and decision making.
The manuscript is well written and free of technical errors, well structured, appropriate in length. All figures and tables are high-quality and reader-friendly. The conclusions are clear and precise. The results obtained in this study are highly relevant to assess effectiveness of GLOF DRM measures not just in Ala-Archa valley but globally. I definitely support publication of the manuscript.
I have just minor comments:
Lines 80-85 – I am not pretty sure that 2015 debris flow in Aksay catchment has been caused by the Uchitel Lake burst. Most probably it was a result of the Aksay lake (cavity) burst.
Line 125 (Fig.4) – it will be better to add isolines or cross-sections of the Aksay river bed add deflection dam to illustrate why this dam should be expanded significantly.
Lines 165-170 - The Uchitel Lake is located near the Uchitel Glacier terminus, so projected retreat of the Aksay glacier will not directly cause expansion of the lake. But the Uchitel Glacier will also retreat. A bit more detailed sketch map with both glaciers and lakes (+Aksay) will be useful.
Lines 175-180 – I fully agree with discharge estimates, but values listed in the text are maximum debris flow discharge and are much higher than initial outburst discharge. It is necessary to specify it in the text and explain how these values were used in RAMMS simulation.
Line 200 - only flow height for the discrimination of high and medium intensity… It is quite reasonable, but what flow height corresponds to high/ medium intensity or hazard? Please specify the values.
Line 295, Fig.8 – it will be better to show location of the deflection dam at the map.
Citation: https://doi.org/10.5194/egusphere-2025-290-RC1
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