MORPHOMETRIC ANALYSIS OF MEANDERBELTS IN THE RIO GRANDE DELTA, A TEST OF HUMAN INTERVENTION

Human interventions on the watershed of the Rio Grande date back to the 1850s when large irrigation projects in New Mexico and Colorado appropriated the base flow of the upper river significantly reducing water discharge in the Gulf of Mexico. Two large dams, Amistad and Falcon, built on the lower Rio Grande, as well as numerous smaller dams on major tributaries have effectively terminated sediment delivery to the delta plain, forcing the river to adjust its channel morphology to the new set of conditions.

Here we compare morphometric analyses performed on the present-day channel of the river with similar measurements from eight meander belts on both the Texas and the Mexican side of the Rio Grande Delta to assess the river’s response to anthropogenic modifications. The rational of this approach is that the old meanderbelts reflect channel morphology of pre-dam river discharge, whereas the morphology of the present-day channel reflects post-dam reductions on water and elimination of sediment delivery. The analyses are being performed on typical 10 to 12 km long stretches of meanderbelts, using 2017 Google Earth imagery, and included comparisons of river sinuosity, meanderbelt width, meander wavelength, meander height and channel width. Preliminary findings suggest that high (>2) channel sinsuosities endure on both the present-day channel and the old meanderbelts. There is an apparent reduction in channel width from 78±4 meters at Resaca de Los Cuates, to 31±5 on the present day channel.