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Once encompassing over 350,000 acres of freshwater tidal marsh, California’s Sacramento-San Joaquin Delta was home to an astonishing array of endemic species. Today, the delta is one of the most transformed landscapes in the world. This previously-rich habitat has been converted into a mosaic of islands tenuously protected by a network of fragile levees and growing economically tenuous crops.
Despite its wholesale transformation, the delta still provides critical habitat for a suite of endangered and declining species. It is also the water conveyance system for 23 million Californians and an eighteen billion dollar agricultural economy.
However, both the delta ecosystem and its water supply are at risk of permanent and catastrophic failure if the delta’s fragile levees collapse during an earthquake or flood. The odds of a catastrophic levee breach over the next fifty years are greater than one in four. Because the levees’ foundations are prone to liquefaction during a seismic event, simply making them bigger and stronger will not appreciably reduce this risk.
Urban sprawl on the edge of the delta threatens to make the problems facing this critical resource more intractable. Over the last decade, thousands of homes have been built, and 125,000 new residential units are already approved for construction over the next ten years. If this trend continues, the entire delta will be ringed by urban development by 2030. Urbanization behind the delta’s levees degrades delta water quality with urban run-off, threatening delicate ecosystems and water supply for much of the state. Placing people and their homes in harm’s way will necessitate new constraints on the management of upstream flood control and water supply reservoirs.
Since 1989, the Natural Heritage Institute has developed strategies to restore stability and sustainability to the delta. NHI has launched several initiatives to tackle the complex web of problems that threaten the continuing viability of the delta’s ecological and water supply systems.
Restoration is the solution that is most likely to protect this critical resource over the long term. Together with our partners, NHI is working to restore tidal wetlands and physically rebuild subsided Delta islands. For example, we evaluated techniques for strategically rebuilding the delta’s islands to sea level so that they can be restored to tidal marsh. Recognizing the high level of uncertainty inherent in such large-scale restoration efforts, NHI pursues an adaptive management approach.
NHI is also working to address the problems associated with rapid urban development in the region. In northeast Contra Costa County, we initiated the Dutch Slough project to restore 1,200 acres of tidal marsh in place of 4,500 homes that had been approved for construction behind levees. We have also forged a partnership with UC Berkeley to initiate a stakeholder-driven sustainable land use plan for the region.
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