Bank De-Stabilization: Allowing for Natural Processes in a Controlled Environment

Invasive trees, including salt cedar and Russian olive, are actively being removed from the Middle Rio Grande riparian forest (bosque). The reasons for removing the invasive species vary from restoration to fuel reduction to recreation. In many instances, invasive trees along the banks are left in place to provide erosion protection. Conversely, several restoration projects have employed mechanical alteration of banks to promote over-bank flooding. The over-bank flooding allows the native vegetation to thrive and is necessary for germination of the native cottonwood trees. During the summer of 2003, with help from the City of Albuquerque Open Space Division, we established three sites to measure, monitor, and compare the changes in the bank of the Rio Grande with and without the removal of Russian olives. Russian olives were completely removed from one 12 meter section of river bank, while Russian olives were cut off near the base (leaving the roots) of a second 12 meter section. Another 12 meter section of bank was unaltered and used for a control site. Sixteen erosions pins (above and below the water level) at each of the three sites were installed and data collection began in June of 2003. During the summer and fall of 2003, erosion due to fluvial processes was negligible while wind and rain contributed to minimal erosion. The snowmelt season of 2004 caused a large increase in the Rio Grande water flow causing all of the erosion pins to be submerged. Monitoring erosion rates of the banks will allow for prediction of future erosion rates and their impact on over-banking.