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Acreage/Location
The Porter Marsh Complex, located at the head of Elkhorn Slough, is approximately 246 acres (between Elkhorn Road and Blohm Road).
Past Human Activities (Modifications/Restoration/Management)
A railroad embankment and bridge was built in 1872 between the Porter Marsh Complex and the main channel of Elkhorn Slough. A wooden bridge, constructed in the past to permit passage over the Porter Marsh Complex, allowed tidal and freshwater exchange.
 
Cattle have grazed parts of the Porter Marsh Complex since the mid 1800’s. In the 1940s, a large earthen dam was constructed at the southern end of this area for the purpose of impounding freshwater and restricting tidal inundation to the northern areas. Around the same time, it was observed that water tables were being lowered by land use which reduced the flow and presence of freshwater springs and altered surface flows from Caneros Creek.
 
 
The construction of the Harbor in 1947 increased tidal inundation to the Porter Marsh Complex. Around 1951, a linear section of Porter Marsh was filled for the construction of Elkhorn Road for its present-day alignment creating a permanent berm that obstructed tidal water exchange. Culverts and flap gates were purchased by the Moss Landing Harbor District Commission and installed by Monterey County under the road to allow one-way flow from Porter Marsh to Elkhorn Slough. In the early 1980s, Monterey County performed maintenance work on this berm to build up the road and also likely repaired the water control structure. The 1989 earthquake destroyed the flap gates and caused the road to subside. From 1989 to 1995, tidal waters regularly flooded the Porter Marsh Complex (beyond the extent that received tidal inundation just prior to the Harbor construction in 1947). In 1996, Monterey County Public Works installed new culverts and flap gates under Elkhorn Road with state and federal funding.
 
 
Current Management/Ownership
 Monterey County is responsible for maintaining Elkhorn Road and associated culverts. The Nature Conservancy owns and the Elkhorn Slough Foundation (ESF) manages the majority, 159 acres, of the Porter Marsh Complex. ESF also holds a conservation easement on 35 acres in this area. Fifty-two acres of Porter Marsh are not under any conservation protection. In the past few years, Mosquito Abatement has periodically cleared the flap gates of debris and non-native tubeworm reefs to keep the flap gates functional to reduce mosquito populations.
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