RESTORING THE LOST RESACAS: WETLAND RESTORATION IN THE LOWER RIO GRANDE VALLEY, TX.

Abstract

This research presents a collection of ecological strategies for the restoration of vanished resacas, oxbow wetland lakes in the Lower Rio Grande region, which have significantly declined in the past decades. As a result, the Lower Rio Grande, an underserved and largely Hispanic area, is facing threats of declining water quality and quantity. Using a 344-acre park in Mercedes, TX as a study area, the restoration of the lost resacas brings back the native resacas ecosystem, achieves flood control, purifies the water, revitalizes vacant land, and provides a safe route for student travel. Currently in Mercedes, flood control projects and agricultural practices have altered the natural levees and decreased biodiversity, causing bacterial water pollution issues. The floodway divides the city; it is further divided by highways and railway, causing a lack of green space in this largely Hispanic area, and resulting in human health problems. As a vital portion of the wetland system, resacas accommodate various species and vitalize biodiversity in the Lower Rio Grande Area, which is the convergence of the Central Flyway and the Mississippi Flyway. A suitability analysis was conducted to identify potential habitat areas and select the optimal design site by identifying available vacant land. A resacas network for wildlife habitat was then created, a comprehensive site analysis was conducted, and design decisions about the form of the restored resacas were made. Three types of barriers were identified: recreational, mobility & safety, and population-based. Correspondingly, resacas-ready programs were generated to break down each barrier. Outputs from the application of the Long-Term Hydrologic Impact Assessment Model (L-THIA) show that through restoring the resacas, 1,486,703 ft3 of additional annual stormwater runoff is captured, reducing 89.5% of phosphorous in the contaminated soil, 86.4% of suspended solids, and 84.1% of fecal coliform from the currently polluted water, significantly contributing to the local environment and public health.