REHABILITATION OF THE MIDDLE RIO GRANDE NEAR BERNALILLO, NEW MEXICO

摘要

Along the Middle Rio Grande near Bernalillo, New Mexico, sediment loads and flood peaks have been reduced, and the river channel is incising and has converted from a low flow braided sand-bedded channel to a single thread gravel-controlled bed channel (often bi-modal sediment transport conditions), with a slightly sinuous planform. As a result, the river has migrated laterally, and before the project, was closer to the levee that provides flood protection for the adjacent developed areas. A project has been implemented to prevent levee failure, safely pass peak flows, re-establish some measure of floodplain connectivity, and improve habitat conditions for two endangered species. Project features include a new channel relocated away from the levee, bendway weirs, a low floodplain surface along the outside of the new river bend, a secondary channel, rootwads, and native vegetation plantings. The new low floodplain surface is intended to provide a new riparian zone near the existing riparian zone that has become decadent as a result of channel incision and reduced flood peaks. Data include post project cross sections showing the re-connected floodplain and the initial riparian zone reestablishment, and main channel and near bank vertical velocity profiles. Initial channel response is qualitatively evaluated.