Hazard assessment of the potential outburst flood of the Ikhnach Lakes, Uzbekistan

Glacier lakes outburst floods (GLOFs) study in the Central Asian region is a very important task in terms of global warming and glacier shrinking. It is expected that ongoing climate changes will lead to an increase in the magnitude and frequency of glacial hazards with profound implications for risks. The appearance and expansion of naturally-dammed lakes in the mountain regions of Uzbekistan poses a threat to downstream communities through the potential for sudden drainage.In this study, we considered a possible flood from failures of natural dams of the two well-known Ikhnach lakes located in the Pskem River basin at an altitude of 2400 m. We simulated the GLOF using the RAMMS: DebrisFlow software. In our scenario the potential debris flow from the Ikhnach Lakes can reach a constructed dam of the Pskem new reservoir located at the altitude of 1020 m. The total length of the analyzed flow path is 34 km. It is known that accurate and up-to-date digital elevation models (DEMs) are important tools for studying mountain hazards. We used such global DEMs as input as ALOS PALSAR, and TanDEM-X DEMs. According to the simulation results of possible floods from the Ikhnach lakes in the Debris Flow module of the software, the following results were obtained: (i) the time of the flood to reach the hydropower station (HPP) area - 14800±700 sec ~ 4.11 hours; (ii) maximum water discharge of flood water at the HPP area – 410±20 m3 s-1; (iii) height of the flood in the HPP area - 1.2 m.The obtained results show that there is no potential disastrous effect of the possible flood from the lakes to the residential area as the lowest settlement along the river bed is located considerably higher than flood risk area. However, possible floods in the lakes potentially can reach and have an effect on day to day dam operation of newly constructed Pskem HPP and its engineering infrastructures. Therefore, flood parameters modeled in the RAMMS can be useful information for designing flood damage prevention structures and reservoir operation.