Complex River-Wetland Corridors

Wetland Creation

Process-based river restoration leads to the development of complex river-wetland corridors. A river-wetland corridor is an interacting system of channels, wetlands, floodplain ponds, and lakes. Once upon a time, river-wetland corridors were wet, widespread, and ecologically productive--and they could be again. A complex river-wetland corridor is one where there is connectivity between surface and subsurface water. River-wetland corridors are "dynamically stable" and resilient due to their capacity to make continuous, small adjustments that accommodate fluctuations in the influences of hydrology, geology, and animal and plant life on the river's form and process.

Between the 1780s and the 1980s, six states drained more than 85% of their wetlands and a further 16 drained at least 50%. In the central prairies,  more than 75% of riverine wetlands along the Platte River have been drained and half of all riparian areas in the arid to semiarid western United States, including their riverine wetlands, have diminished vegetation cover. River-wetland corridors across the United States have been lost due to channel instability and the simplification of rivers from multi-thread to single-thread channels. The reason for this loss of river-wetland corridors include disconnection of a river from its floodplain, dam construction, river regulation, floodplain drainage, artificial levees, restoration to a stabilized single-thread channel, urbanization, overgrazing of riparian vegetation, and extirpation of beaver populations.

Wetlands store water during large precipitation events and allow for a slow release, reducing storm-water runoff and erosion. According to the Federal Emergency Management Agency, there are roughly 225,000 properties in the 100-year floodplain in Illinois. On paper, there is a 1 percent chance each year that these properties could be inundated with flooding. Unfortunately, 100-year flood events are becoming much more frequent. CLICK HERE to find out more about why we need more floodwater storage capacity in Illinois.

Functional river-wetland corridors provide both abundant and diverse aquatic and riparian habitat and corridors for species migration and dispersal. CLICK HERE to read more about how wetlands create habitat and foster biodiversity.

And, of course, river-wetland corridors remove nutrients from incoming waters in multiple ways. Wetlands are able to remove nitrogen and phosphorus through a combination of physical, chemical, and biological processes. These naturally occurring processes adsorb/absorb, transform, sequester, and remove the nutrients and other chemicals as water slowly flows through the wetland. CLICK HERE to find out why we need nutrient removal in Illinois.

Before and after: Doty Ravine Preserve in 2017 and 2019 (courtesy of USFWS). Source: Placer Land Trust.