Movie:Debris Flow Nepal


Information Page: Debris Flow Nepal

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Dam burst and Seti River Debris Flow

Key Attributes

Domain: terrestrial, hydrology, environmental controls
Keywords: upstream rockfall, lake dam burst, river surge with sediment and debris
Model name: Animation model name
Name: unknown, unknown
Where: Seti River, Pokhara, Nepal
When: May 5th, 2012

Short Description

Grade level: Middle (6-8), High (9-12), Under graduate (13-16)

Statement: Hyperconcentrated water in Seti River after rockfall triggered an upstream dam burst

Abstract: A series of landslides occurred in late April and May 2012 in the headwaters of the Seti River. These caused a landslide dam wall, which blocked the normal flow of river. Seti river means 'White River', because it normally has the typical milky color of rivers that drain a glaciated area. However, because the river was bloked it was unusually clear, untill May 5th. Early in the morning of May 5th, 2012 a large rockfall occurred high on the ridgeline of the Annapurna massive, the rock and debris came down with tremendous force. Along its steep course the rock melted snow and ice and picked up more debris. This debris and te floodwave hit the dammed up Seti River and caused the earlier landslide dam to abruptly break.

The video shows the slurry of water and sediment traveling through the Seti River valley. The initial pulse of debris and hyperconcentrated muddy water damaged many houses and probably 72 people were killed. This region is conducive for these natural hazards, the relief is extremely high and avalanches and rockfalls are common. The downstream rivers have eroded into lake bed sediments and thus can easily erode more. Furthermore the monsoonal climate of the region can trigger unstabilities due to high rain events.




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