Hilly regions like the lower Himalayas, which are highly susceptible to landslide, are also exposed to the peril of flashflood due to landslide. Say if we take an example of the location of the site for the upcoming formulation unit of CIPLA at Sikkim, situated beside a stream "rongpo chu". A landslide at the upstream due to earthquake or prolonged rainfall can create a dam of material shaken loose during the event. Accumulation of water behind the dam would eventually create a giant lake. The lake fills to the top of the landslide dam and then spills over the top. Because the landslide is very fragmented, the water cuts down through it and you get a very rapid release of the lake water washing every thing downstream.

It's important to asses the catchment areas of such small streams. Monitor the level of stream during prolonged rainfall, after an earthquake. At the knowledge of such a lake being formed a drainage channel - known as a spillway - needs to be built to empty the lake.