Laguna Grande/Larga Wetland Restoration: Conceptual Design Development

The Laguna Grande/Larga Concession Area is an approximately 320-acre site located on a historic meander of Reach 4 of the Colorado River, near Francisco Murguía, B.C., Mexico. The NGO team of Restauremos el Colorado, A.C., Pronatura Noroeste, A.C., and the Sonoran Institute is evaluating conceptual methods to improve and restore native aquatic, wetland, riparian, and upland vegetation to a site dominated by salt cedar and phragmites. The concept plan is designed to capitalize on floodwaters of the Colorado River and allocated irrigation water delivered through existing canals to support a mosaic of backwater wetlands, cottonwood-willow gallery forests, mesquite bosques, and upland habitats. In addition to restoring native ecosystems, the projects hopes to bolster the economies of nearby farming communities and ejidos through job creation. Conceptual restoration activities include: selective hand and mechanized clearing of invasive reeds and salt cedar while leaving existing native trees, earthwork/re-contouring to optimize water use and habitat, installation of infrastructure to allow for managed flooding, and planting with native cottonwoods-willow, marsh plants, upland grasses, and honey mesquite. The restoration design is expected to attract native and migratory birds and wildlife species.

The following is a summary of Oxbow Ecological Engineering’s technical contribution to the project:

Conceptual Analysis – Oxbow Ecological Engineering processed USGS/USBR LIDAR point cloud data that was collected for entire Colorado River Delta and extracted over 20 million “bare earth” points for the Laguna Grande/Larga Concession Area. The bare earth points were combined with RTK GPS bathymetric data, collected by OEE during ground-truthing operations, to create an existing ground surface model (TIN-Triangulated Irregular Network) for the site. This surface model was then leveraged to complete a wide array of analyses, calculations, and mapping including: habitat and water optimization, conceptual habitat maps, water extent and depth maps, and preliminary plan quantities for earthwork and plants.
Conceptual Wetland Design – Provided analysis for the grading and water control plan including earth balance calculations for embankments and habitat channel excavations, technical guidance on cast-in-place water level control structures, and the development of preliminary seasonal water maintenance hydrographs. This concept was then presented to project cooperators in Mexicali, Mexico.
Conceptual Revegetation Plan Collaboration – Coordinated and collaborated with Fred Phillips Consulting, Inc., as needed, as part of the development of the grading and revegetation plan.