Bateman Island Causeway & Yakima Delta Assessment
Figure 1: Aerial view of the Yakima Delta. Photo credit: Benton Conservation District.
Bateman Island sits at the confluence of the Yakima River with the Columbia River, in the City of Richland, WA. The 160-acre island has a rich cultural history and the area is now used for boating, fishing, wakeboarding, birdwatching and hiking. Recreational access to the island is via a 500-foot long earthen causeway. Aerial photos suggest the causeway was constructed between 1939 and 1940 for agricultural access. The US Army Corps of Engineers purchased the island in the 1950’s, prior to the filling of the McNary pool. Bateman Island is leased to the City of Richland under a 50-year agreement. The causeway has no culverts and does not allow water to flow along the south side of the island. Yakima River water backs up to the west of the island and gets heated by sunlight, resulting in very high summer water temperatures.
In 2007, the WA Salmon Recovery Funding Board funded an assessment of the lower Yakima River in Benton County. Data gathered by Benton Conservation District in 2008 and 2009 show that the confluence maintains the warmest surface water temperatures within the lower Yakima River during the summer months. Thermal imaging data indicated that the warmest waters in the lower Yakima River were within the confluence, specifically within the stagnant pools behind Bateman Island. Based on this assessment, the Yakima River Delta and Bateman Island Causeway were identified as high priority restoration actions.
Figure 3: Forward-looking infrared image of the Yakima Delta in August, 1997.
Since 2011, a technical advisory group has met regularly to provide input to studies that modeled and predicted how modifying the Bateman Island Causeway would change river flow and water temperatures around the island. These studies show that improving flows around the south side of Bateman Island would improve conditions for salmon and steelhead listed under the Endangered Species Act by:
- Improving survival of juvenile salmon and steelhead migrating through the Yakima delta,
- Improving rearing habitat for juvenile samlon and steelhead,
- Reducing opportunities for invasive species to prey on juvenile salmon and steelhead, and
- Increasing numbers of adult salmon that make it safely upstream to spawn.
The work is detailed in a final report entitled Bateman Island Causeway Modification Conceptual Design Report. The executive summary is here. For a copy of the full report, contact email@example.com.
Fisheries organizations, including Mid-Columbia Fisheries Enhancement Group and the Washington Department of Fish and Wildlife, would like to further explore options for allowing the Yakima and Columbia Rivers to flow around the southern end of Bateman Island. These options have not been fully developed. Because the causeway has a significant negative impact on fish species listed under the Endangered Species Act, some modifications to the causeway are likely to be needed in the future to improve conditions for fish. We hope the future project will improve salmon habitat while accommodating human use of Bateman Island.