The West Delta is an extremely important asset that protects against migration of salt water, which in turn ensures water quality for upstream uses (including potable and agricultural uses). The West Delta also provides (and has the potential to provide additional) habitat for plants and wildlife in a geographical area with a rapidly growing population that is creating habit loss.
Because of the West Delta soil make up (peat soils) and land management practices (farming or other practices that promotes oxidation of the peat soils) over the years, island subsidence has been occurring at rapid rates. This subsidence jeopardizes levee stability and creates a larger void for saltwater penetration in the event of a levee breach creating a “Big Gulp” effect.
Because of the importance of the West Delta, the State of California purchased much of the land on both Sherman Island (approximately 90%) and Twitchell Island (approximately 80%) in the early 1990s by utilizing State Water Contractor funds. Justification for the purchase of this land includes protection of levees to ensure water quality and creation of habitat. These lands are owned and managed by the Department of Water Resources.
Additionally, research has shown that utilizing certain types of plants and implementing specific land use management practices will not only limit or reduce the oxidation of peat and land subsidence, but also could sequester atmospheric carbon and/or other greenhouse gasses. Because of this potential benefit, carbon sequestration should be a key consideration when evaluating potential land use practices.
In order to limit the rates of subsidence and promote carbon sequestration, the Department Director has directed staff to implement large scale efforts to develop sustainable practices to achieve the goals of reducing subsidence, facilitating carbon sequestration, and developing habitat on both Sherman and Twitchell Islands. In order to implement this directive, FESSRO's Delta Levees and Environmental Engineering Branch will work closely with stakeholders to develop specific projects in a timely manner to achieve these goals.