Case Study: Monitoring and Adaptive Management Saves Money and Extends Functional Life of Middle Rio Grande Habitat Restoration Projects; Todd Caplan

¹GeoSystems Analysis 

²N.M. Interstate Stream Commission

³GeoSystems Analysis 

⁴University of New Mexico

 

This presentation provides a case study demonstrating that maintaining ecological functions of riverine habitat restoration projects through a coordinated monitoring and adaptive management strategy is an essential step towards achieving endangered species recovery goals along highly regulated rivers. Eleven restoration projects were constructed along the Middle Rio Grande between 2016 and 2019 along a 30-mile river reach between Sevilleta National Wildlife Refuge and Socorro, New Mexico. All projects involved mechanically lowering elevated floodplain terraces to promote overbank inundation at discharges between 800cfs and 2000cfs. The chief objective was to create favorable habitat conditions for spawning and rearing silvery minnow along river segments with inherently low channel habitat complexity. While all eleven projects were designed to provide off-channel habitat at low to moderate discharges, the construction period coincided with above-average and prolonged snowmelt runoff. A comprehensive effectiveness monitoring program documented that biological and physical success criteria were achieved at the design discharge, but that sediment plugs deposited along backwater channel inlets would prevent all project sites from functioning at the design discharge without adaptive management intervention. Nonetheless, topographic surveys revealed that the volume of deposited sediment was relatively small compared to amount removed during construction, even after above-average discharge events. This case study highlights that rehabilitating and maintaining ecological functions along highly regulated rivers is achievable and cost-effective, particularly when guided by structured monitoring and adaptive management programs.