Regulation of non-wetland riparian areas in the arid and semi-arid southwest: Section 404 of the Clean Water Act, bank stabilization, and a policy recommendation

Riparian areas are known for being important components of the hydrologic system and rich in biological diversity. In the southwestern United States, the functions provided by riparian areas to the aquatic environment are made more important due to the general scarcity of water. However, many riparian areas in the southwest are not regulated under Section 404 of the Clean Water Act---the principal federal regulation protecting aquatic resources. This lack of regulation has contributed to a steady decline in riparian acreage and condition. For my dissertation I investigated factors associated with permitting bank stabilization under Section 404 of the Clean Water Act in the arid and semi-arid southwest. Bank stabilization was used to assess impacts in riparian areas because it has both a direct negative impact to riparian areas located in jurisdictional waters of the U.S. and also indicates where development has encroached into riparian corridor located outside of waters of the U.S.; Bank stabilization occurs throughout the southwest, but is concentrated in the most populous counties located in coastal southern California. A positive linear relationship was found with the permitting of bank stabilization in this semi-arid region and annual rainfall totals (in particular immediately following El Nino events). The demand for bank stabilization will also likely increase in the arid southwest as the region's population continues to grow rapidly. The data showed that bank stabilization occurs significantly more often when development is placed close to the edge of bank and on the outside bend of a meander. The construction of bank stabilization also appears to lead to the construction of additional bank stabilization and a progressive channelization of the region's waterways. Therefore, to preserve the integrity of the region's aquatic resources and better meet the objective of the Clean Water Act, it is imperative to regulate development in riparian areas located adjacent to waters of the U.S. I argue that non-wetland riparian areas in the southwest be classified as special aquatic sites under the 404 regulations because it would be scientifically justified and also provide non-wetland riparian areas the same regulatory protections that wetlands currently receive.