Distributions of woody vegetation on floodplain surfaces affect flood-flow erosion and deposition processes. A large flood along the lower Rio Puerco, New Mexico, in August 2006 caused extensive erosion in a reach that had been sprayed with herbicide in September 2003 for the purpose of saltcedar (Tamarix spp.) control. Large volumes of sediment, including a substantial fraction of sand, were delivered to the reach downstream, which had not been treated with herbicide. We applied physically based, one-dimensional models of flow and suspended-sediment transport to compute volume concentrations of sand in suspension in floodplain flow at a site within the sprayed reach and at a site downstream from the sprayed reach. We computed the effects of drag on woody stems in reducing the skin friction shear stress, velocity of flow, and suspended-sand transport from open paths into patches of dense stems. Total flow and suspended-sand fluxes were computed for each site using well-constrained flood-flow depths, water-surface slopes, and measured shrub characteristics. Results show that flow in open paths carried high concentrations of sand in suspension with nearly uniform vertical distributions. Drag on woody floodplain stems reduced skin friction shear stresses by two orders of magnitude, yet sufficient velocities were maintained to transport sand more than 50 m into fields of dense, free-surface-penetrating stems. An increase in shrub canopy extent from 31% in the sprayed reach site to 49% in the downstream site was found to account for 69% of the computed decrease in discharge between the two sites. The results demonstrate the need to compute the spatial distribution of skin friction shear stress in order to effectively compute suspended-sand transport and to predict the fate of sediment and contaminants carried in suspension during large floods.
|Title||Effects of woody vegetation on overbank sand transport during a large flood, Rio Puerco, New Mexico|
|Authors||Eleanor R. Griffin, Mariela C. Perignon, Jonathan M. Friedman, Gregory E. Tucker|
|Publication Subtype||Journal Article|
|Record Source||USGS Publications Warehouse|
|USGS Organization||National Research Program - Central Branch|
Lower Rio Puerco geospatial data, 1935 2014
Jonathan Friedman, Ph.D.
Lower Rio Puerco geospatial data, 1935 2014A long-term study of the geomorphic history of the lower Rio Puerco arroyo in north-central New Mexico included the collection of high-precision (Real-time kinematic) GPS survey data, registration and rectification of historical aerial photographs, an aerial LiDAR survey, and acquisition of post-flood satellite imagery. Mapping of geomorphic features from the aerial photographs and satellite image
Jonathan Friedman, Ph.D.