Marshes along rivers provide important sediment filtration and settling, and nutrient reduction along rivers. They also provide habitat for creatures such as the little broad-nosed bat. Marshes can reduce the risk of downstream flooding during heavy storms. Removal of marshland along the Mississippi River has increased the risk of flooding along the river. In some areas, upstream use of river water for municipal and agricultural use can reduce the magnitude of river flooding to adjacent marshes and lead to reduction of marshland.
Salt marshes are large ecosystems alongside oceans.
Changing the hydrology of salt marshes can severely reduce the diversity of wildlife at a marsh. For example, salt marshes near the Kennedy Space center were impounded by dikes and flooded during mosquito season. As a result, plants in the marsh died. Prairie potholes are common in the Midwest. The landscape is a series of potholes with poorly drained soils in the bottom of potholes and well drained soils along the high areas.