Overall opinion on the effectiveness of dams and reservoirs

Dams help in preventing floods. They catch extra water so that it doesn't run wild downstream. Dam operators can let water out through the dam when needed. The first upstream flood control dam was built in 1948, Cloud Creek Dam in Oklahoma.

People build reservoirs because the amount of water in a river varies over time. During very rainy times or when mountain snow is melting, the water in a river rises and sometimes overflows its banks. By limiting the amount of water allowed to continue downriver, reservoirs help control flooding.

Explanation:

i think the answer to your question is: settlement of the interior and economic growth. ( ^_^)／