Controlling the river flood. R iver flooding, while often more damaging to property, is much easier to predict. The land around a river is called a watershed. It's collecting water over a broad area and funneling it this narrow strip that is the river. Residents and scientists can tell when there has been an unusual amount of snow and rain, and they can see the river getting higher everyday.
Early prediction gives emergency officials time to evacuate residents in the danger areas.
For example, during the spring of 1997, the heavy flooding of cities along the Red River in North Dakota and Minnesota was predicted two months in advance. Another winter-related cause of river flooding is ice jams. At times, large chunks of floating ice will pile up if they hit bend, bridge or other obstruction and stop the river's flow. The traffic backs up. The '97 floods in the Upper Plains states were caused by heavy rainfall during the fall.