Abstract
Author(s): Durand, John R. | Abstract: https://doi.org/10.15447/sfews.2017v15iss4art4 Large tracts of land in the Sacramento-San Joaquin Delta are subsided due to agricultural practices, creating polders up to 10 m below sea level that are vulnerable to flooding. As protective dikes breach, these become shallow, open water habitats that will not resemble any historical state. I investigated physical and biotic drivers of novel flooded polder habitat, using a Native Species Benefit Index (NSBI) to predict the nature of future Delta ecosystems. Results suggest that flooded polders in the north Delta will have the ecology and fish community composition of a tidal river plain, those in the Cache-Lindsey Complex will have that of a tidal backwater, those in the confluence of the Sacramento and San Joaquin Rivers a brackish estuary, and those in the south Delta a fresh water lake. Flooded east-side Delta polders will likely be a transitional zone between south Delta lake-like ecosystems and north Delta tidal river plains. I compared each regional zone with the limited available literature and data on local fish assemblies to find support for NSBI predictions. Because flood probabilities and repair prioritization analyses suggest that polders in the south Delta are most likely to flood and be abandoned, without extensive intervention, much of the Delta will become a freshwater lake ecosystem, dominated by alien species. Proactive management of flooded tracts will nearly always hedge risks, save money and offer more functional habitats in the future; however, without proper immediate incentives, it will be difficult to encourage strong management practices.
Highlights
Twentieth-century land-use practices have accelerated land subsidence and polder formation around the globe, especially where land reclamation is combined with intensive agriculture near rivers and estuaries (McCreary et al 1992; Lindenschmidt et al 2009)
Most are subsided below sea level, deepening with proximity to the San Joaquin River corridor
The east-side polders have elevation gradients that are probably desirable for some wetland and subtidal restoration purposes, but they are limited by low flows and clear water
Summary
Twentieth-century land-use practices have accelerated land subsidence and polder formation around the globe, especially where land reclamation is combined with intensive agriculture near rivers and estuaries (McCreary et al 1992; Lindenschmidt et al 2009). SAN FRANCISCO ESTUARY & WATERSHED SCIENCE they are inundated These lands are highly altered from their original form, and will form novel aquatic habitats with largely unknown consequences for resident species. Subsidence was accelerated by soil oxidation and compaction from agriculture, reducing elevation as much as eight m below sea level in some cases (Weir 1950; Mount and Twiss 2005). These polders are vulnerable to flooding when levees collapse because o poor building materials, age, floods, earthquakes, and sea level rise While there is considerable political will to restore parts of the Delta to support native fishes that are threatened or endangered (ICF International 2013), how flooded polders will support or work against these goals is poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
