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Acreage/Location
The Parsons/South Marsh Complex (including Five Fingers) is located on the southeastern side of Elkhorn Slough. The entire complex is approximately 415 acres in size and the main areas are dominated by mudflat areas with some subtidal creeks, fringing tidal marsh, and created tidal marsh islands.
 
Past Human Activities (Modifications/Restoration/Management)
In the past, the Parsons Slough/South Marsh Complex was dominated by tidal salt marsh and tidal creeks. In 1872, a railroad was built along the western side of this area and this railroad embankment blocked off the connections of about half a dozen tidal creeks. Railroad bridges were constructed over two of the main tidal creeks (mouth of Parsons Slough and just south of Hummingbird Island) allowing these connections to remain open. In 1902, a group of San Francisco businessmen purchased the land of South Marsh and started the Empire Gun Club. By 1913, this group created a number of large, artificial freshwater ponds (converted from tidal marsh) in the South Marsh area using earthen dams to enclose the areas and pipes to convey water from freshwater springs for the purpose of encouraging waterfowl prized for hunting. A few large, artificial freshwater ponds had also been created in Parsons Slough for duck hunting by 1913. One of these large ponds was created by blocking off four of the six fingers of Parsons Slough with an earthen dam.
 
 
In the 1920s, J. Henry Meyer purchased the South Marsh property and the Elkhorn Dairy was established. By 1956, the entirety of South Marsh was enclosed with large levees, cleared, leveled, and drained, converting the tidal marsh and duck ponds to pastureland for dairy cattle. This diking blocked one of the two remaining tidal creeks to South Marsh just south of Hummingbird Island and separated South Marsh from Parsons Slough (except for 1-2 areas in the levees that look like they may have had some sort of water control structures that could have been used as drainage during heavy rain events). Another levee, constructed across the mouth of Parsons Slough between 1949 and 1956, completely removed the remaining major tidal creek and marsh areas from tidal exchange. This levee may also have contained some sort of water control structure such as a flap gate that could have been used to facilitate drainage of water out to the main slough during this time. The draining of the tidal marsh areas in the Parsons Slough/South Marsh Complex between 1931 and 1956 caused the marsh sediments to dry out, compact, decompose, and subside by several feet. Between 1956 and 1980, a levee breach opened four of the six fingers of Parsons Slough perhaps and allowed flood waters to drain into Parsons and the main slough.
  
In 1980, part of Elkhorn Slough (including the majority of the Parsons Slough/South Marsh Complex) was purchased and designated as a National Estuarine Sanctuary. The Elkhorn Slough National Estuarine Research Reserve (Reserve), as it is now known, is one of a network of 27 protected areas nationwide that were established for long-term research, education and stewardship through federal-state partnerships. The Reserve is owned and managed the California Department of Fish and Game (CA DFG) and is administered by the National Oceanic and Atmospheric Administration (NOAA).
Soon after the Reserve was designated, planning efforts were started with the purpose of returning the grazing land of South Marsh to wetland. The proposed plan consisted of creating four experimental tidal salt marsh (including tidal creeks, mudflats, and islands) areas at two different scales behind levees and dams (that could be manipulated), two smaller freshwater wetlands, and causeways for public access on 50 acres. Sediment would have to be excavated to create the tidal creeks and built up (with gradual slopes) to create vegetated, tidal marsh. In order to restore tidal exchange to the salt marsh areas, it was proposed that the Parsons Slough-South Marsh levee (just north of the Parsons Mouth levee) would be breached. This wetland plan was submitted for permit approval in 1981.
During winter of 1982-1983, the Parsons Mouth levee breached during a storm event allowing tidal waters to enter both South Marsh and Parsons Slough. There was an attempt to curb the flooding, but the currents were too strong. Even though some of the earthwork had already started in the South Marsh project site, the preparations had to be delayed and eventually when conditions allowed, water was pumped out to finish construction work. During this time, the proposed project plans were changed to a series of straight channels and habitat islands (as we see today) that would receive tidal exchange (changing the focus of this project from more of a replicated experimental approach to a wetland enhancement approach). During the spring and summer of 1983, these new proposed plans were resubmitted for permit approval (as amendments), went out for bid, and channel and island construction began. In the fall of 1983, the Parsons Slough-South Marsh levee was breached restoring tidal exchange to this area. Since that time, pickleweed established on the tops of the islands and small-scale plantings were done in the high marsh areas of South Marsh. Bank erosion has significantly decreased the width and length of these habitat islands since they were first constructed.
  
Because of severe land subsidence that occurred during the years that the wetland was drained and used as pasture, the average land elevation in the Parsons Slough/South Marsh Complex is now approximately 1.9 feet (0.57 meters) above mean lower low water. Apart from a few constructed tidal marsh islands and fringes of tidal marsh adjacent to upland areas, this land elevation currently supports mudflat habitat. In order to support low to middle vegetated tidal marsh, land elevations would have to be between 2.86 and 5.33 feet (0.87 and 1.63 meters) above mean lower low waterand high tidal marsh land elevations would have to be above 5.3 feet (1.63 meters).
 
Current Management/Ownership
The majority of the Parsons Slough/South Marsh Complex (except for a few tips of Five Fingers) is owned and managed by the California Department of Fish and Game as part of the Elkhorn Slough National Estuarine Research Reserve which is administered by NOAA. |
