Damaged Riparian Zones and their Eco-Geomorphic Consequences

Cliff R. Hupp
U.S. Geological Survey, 430 National Center, Reston, Virginia 20192

The riparian zone is a unique environmental setting where terrestrial and aquatic ecosystems overlap. This transitional area allows for the development highly diverse biotic communities within the zone of overlap and provides critical refugia, food sources, and nursery areas for the adjacent ecosystems, additionally, riparian areas (floodplains in particular) may trap and store large amounts of suspended sediment and associated environmental contaminants; intact riparian zones play a major role in natural water-quality processes. Large areas of riparian habitat (including Bottomland Hardwood forested wetlands) have been lost or damaged through dam and levee construction, channelization, and filling particularly in the southeastern United States. Human activities that lead to channel incision (channelization, dams) may locally increase bank erosion and suspended-sediment load and lower the water table on the flood plain leading to tree mortality and wholesale community shifts. The loss of contact between streamflow and the riparian area may have far-reaching downstream effects including reduced sediment and contaminant trapping and increased water velocities (increased bed and bank erosion) leading to an overall decrease in water quality. Concomitant shifts in aquatic habitat and stream regime may also occur. Research and restoration of critical riparian areas will be an important component in the long-term sustainability of aquatic systems and water quality.