Riparian land refers to terrain that is adjacent to rivers and streams and is subject to periodic or occasional flooding. The plant species that grow in riparian areas are adapted to tolerate conditions of periodically waterlogged soils. Riparian lands are generally linear in shape and may occur as narrow strips of streambank vegetation in dry regions of the American Southwest or as large expanses of bottomland hardwood forests in the wetter Southeast. The ecosystems of riparian areas are generally called riparian wetlands. In the western United States, riparian vegetation generally includes willows, cottonwoods, saltcedar, tamarisk, and mesquite, depending on the degree of dryness.

The riparian zone of bottomland hardwood forests can be differentiated into several zones based on the frequency of flooding and degree of wetness of the soils. Proceeding away from the channel of the river, the zones may be described as follows: intermittently exposed...