UNDP Imja Final Report

The Community Based Flood and Glacial Lake Outburst Risk Reduction Project (CFGORRP) intends to reduce human and material losses from a potential Glacier Lake Outburst Flood (GLOF) from Imja Lake (5010 m) in Solukhumbu District by reducing the GLOF hazard risk in 27 downstream settlements by reducing Imja Lake’s level by more than 3 m through construction of an open channel. As a part of the project the task of “Detailed Bathymetric and Hydrologi-cal/Glaciological Assessment required for Structural Design of lmja Lake Lowering” for input to technical design of the Lake lowering was awarded to the JV of ADMC Engineering (P.) Ltd. & DK Consult (P.) Ltd. The survey phase of the larger project was from 30 September to 31 December, 2014, after which the effort has moved to an engineering phase. This project is warranted, as our satellite-image-based time series of Imja Lake shows continued growth on a trend established since the early 1960s; furthermore, the damming end moraine is degrading.

At the survey phase of the project, field work for the bathymetric survey was completed between October 10 – 23, 2014 inclusive. Onsite work was preceded by a 5+ day acclimatization trek (October 5-10) from Lukla (~2840m) to Imja Lake site (~5000m). The bathymetric survey including echosoundings done from a USV (unpiloted surface vehicle) and from a kayak. The USV work was completed between October 11-13, 2014, when the boat’s owner and primary operator, Umesh Haritashya was onsite. Most of the kayak bathymetric survey work was then undertaken. Data gaps remained from the USV-kayak echosounder surveys due to development of unseasonal lake ice, which hindered data acquisition in some parts of the lake and entirely prevented acquisitions in some other small but important areas. To fill the data gaps, additional depth measurements were made by plumb line through augured holes in lake ice to reach high-priority areas where previously we had been unable to obtain measurements or where a higher areal coverage was desired. The team also contacted Professor Daene McKinney and Marcelo Somos-Valenzuela, who had previously obtained a limited set of echo-soundings in 2012. These data were provided to us, thus improving data density and coverage, and were analyzed together with our new measurements.