GEOMORPHIC CHARACTERIZATION OF FLUVIAL LANDSCAPES AND RELATED ENVIRONMENTAL ISSUES

The geomorphic characterization of project sites located on fluvial landscapes should include landform type, origin, distribution, relative age and energy, and their engineering significance. Channel landform characterization should also include stream type and order, flood potential, sediment load composition, material properties of channel bed and banks, and ground water levels. Furthermore, there are three additional interdisciplinary issues pertaining to these landforms that merit consideration. For example, fluvial landforms may be or may have been adversely affected by accelerated fluvial erosion; they often support protected and regulated biological habitats such as wetlands; and they may be the regulated locales of previous cultural activity. In some regions, past modifications of stream systems and/or modification of upland areas have resulted in accelerated channel erosion which may be on-going and may adversely affect the integrity of the proposed project. Channel and upland modifications, respectively, include: changes in the gradient or base level of stream channels through meander cut-offs, in-bed mining or related activities; and changes of land use or land cover of upland areas. Both channel and upland changes may produce higher discharges into regional streams. These discharges result in channel incision and head cutting and may adversely affect the project, fluvial habitats, and cultural sites. The determination that accelerated erosion is occurring or has occurred, would allow for site mitigation and, more importantly, demonstrate that these processes were in effect prior to construction and were not caused by the project. Hydro-geomorphic modeling has become an acceptable form of wetlands classification for mitigation and permitting purposes. Thus, the hydrology and geomorphology of suspected wetland areas should be included in the project characterization. Likewise, characterizing the geomorphic history, age, and relative energy of fluvial landforms would also contribute to the identification and mitigation of cultural sites. Addressing these three interdisciplinary issues, as a part of characterization, will protect project integrity, contribute to the permitting and regulatory process and enhance natural and cultural resource management.