Hard Engineering

Evaluation

Involves using technology to control rivers. Dams prevent the natural flow of a river. A concrete barrier is built across a valley and water fills in the reservoir area behind it. Water released or held depending on current or expected rainfall. 
Straightening meanders is a smaller scale way of managing rivers. Semicircular ways are longer and slower than straight one so water in a meander takes longer to clear area. By straightening them artificially the river follows a shorter and straighter route.