How do people help beavers?

Beavers are now known to help the environment by building dams (known as lodges). The dams created lakes along the rivers and helped to slow down any flooding previously experienced during very rainy weather further downstream. Beavers also kept down the overgrowth of willows, etc, that could flourish too much and choke the rivers. In some places, beavers have been deliberately reintroduced (can't remember where, it was a documentary on the TV).