Much of the discussion in the Dam Break Analysis (Mullaperiyar to Idukki reservoir) done by the Indian Institute of Technology, Roorkee, is about the height and speed of the water flow in case of failure of Mullaperiyar dam. As to the lives of people living downstream of the dam, it matters little whether the water would be flowing in at a height of 40 metres or 20 metres or with a velocity of 40 kilometres a hour. Even water flowing at, say, ten km an hour and a few metres high will claim lives. But width of the flow matters as that determines who all living near the river course would be affected.
The analysis shows that the top width of the flow would be less than 300 metres for the first 30 km of the path of flow along the river course. For the rest of the 15 km before reaching Idukki reservoir, the top width exceed half a km only at two points. However, the accompanying inundation maps show that water could spread out in low lying areas.
The study does not say anything about the chance of small hills or elevated portions on the sides of the river course being breached and water flowing into Pathanamthitta district.
Given below are the inundation maps. They are photographs of the original map prepared by the IIT. The image is not to scale because of distortions resulting from placement of the map and camera perspective. Locational information may be visible only in terms of longitudes and latitudes in the photo except for a few place names such as Vallakkadavu, Vandiperiyar and Upputhara. (The original map is a larger one plotted against a top sheet of 1:25000 scale.)
Split Map 1: