Our administrative system was developed by dividing land based on the population density. Natural boundaries like river basins were totally ignored. Thereafter, due to rapid development and population growth natural forest cover was reduced and riparian zones were destroyed for agricultural and residential purposes. Still we do not have idea about the carrying capacity of central hills and we are increasing the pressure on the natural environment in these areas which is the heart of our country by increasing the population and other land use activities. We are trying to find solution at macro scale. We select larger river basins and try to model flash floods ignoring the micro level destruction happening at the source areas.