Center for Research in Water Resources, University of Texas at Austin
Abstract
A model was developed to assess the impact of a potential glacial lake outburst flood
(GLOF) from Imja Lake in Nepal and its impact on downstream communities.
Implications of proposed GLOF risk reduction alternatives, including one suggested by
local community members, were assessed. Results provided three alternatives that offer
significant risk reduction for the communities, including (1) no lowering of the lake and
constructing a 60 m flood detention dam, resulting in a 43.2 percent reduction of risk, (2)
lowering the lake 10 m with a 40 m dam, resulting in a 57.8 percent reduction of risk, and
(3) lowering the lake 20 m with no dam, resulting in a risk reduction of 66.7 percent. An
alternative to lower the lake by 3 m with no check-dam, currently under consideration by
the Government of Nepal, would result in a 5.2 percent reduction of risk. This alternative
does not appear to offer significant risk reduction benefits to downstream communities
compared to lowering the lake by 20 m. Results suggest that either the lake must be
lowered by significantly more than 3 m (20 m is recommended) or that a downstream
flood detention dam be included in the project. One possible method of lowering Imja
Lake is to use siphons to drain lake water by 3 m, excavate to the new water level,
repeating the process until a total lowering of 20 m is achieved. This method would
require the use of 13 pipes of 0.350 m diameter to lower the lake.Center for Research in Water Resource