Goat Island Marsh Tidal Marsh Restoration & Interpretive Nature Trail
|Sponsoring Agency||Solano Land Trust|
|Watershed Tributary||Suisun Marsh|
|Public or private land?||('Private',)|
|Location (lat/lon)||38.29963889, -122.16427778|
|Location Description||Rush Ranch Open Space Preserve. Suisun Marsh. Grizzly Island Road. Suisun City. Solano County. California.|
The main project actions include lowering the perimeter levee, removing water control structures and creating an oversized channel. Additional actions include weed control and revegetation, expansion of existing ponded areas, and construction of a interpretive nature trail to offset loss of levee trail.
This project aims to restore tidal marsh habitat by reconnecting and reestablishing tidal marsh hydrology and related physical and ecological processes within and around Goat Island Marsh. This project will be implemented in conjunction with construction of an Interpretive Nature Trail to Goat Island Marsh to offset public access impacts resulting from closure of the levee trail.
Part 2 - Detail
The purpose of the Goat Island Marsh Restoration Project is to reinitiate tidal flows to the site and to reestablish characteristic marsh feature (ponds, pannes and SAV areas) and vegetation. The main project actions include creating an oversized channel, lowering the perimeter levee, and expanding existing SAV ponds, active weed control and native species revegetation, and replacing the levee trail with an interpretive nature trail and boardwalk.
Tidal marsh restoration features (Figure 1.2)
· Construction of Tidal Channel & Channel Bank High Marsh Habitat Excavate an oversized (larger than the theoretical equilibrium cross-section for the initial tidal prism) breach and main “trunk” channel sized to prevent tidal choking (constriction of tidal flow, restriction of the basin’s tidal prism). Use spoils from excavation to construct side cast ridges and actively revegetate these areas with competitive, native perennial high brackish marsh species to preempt rapid invasion of Lepidium latifolium, and actively remove pioneer (incipient) small colonies of L. latifolium until native vegetation establishes closed canopy cover.
· Construction of Branch Channels. Improve or establish post-restoration circulation in the new channel via one of the following means:
o If excavation of branch channels (channels branching from the main trunk channel) is cost-effective, then construct highly sinuous and irregular branch channels in selected areas of the subsided marsh plain, patterned after historical tidal channels or local reference channels.
o If excavation/dredging is not cost effective, mow or macerate tule-cattail bulrush in existing subsided diked marsh channels.
· Levee Lowering & Channel Bank Vegetation Enhancement.
o Grade exterior levee to elevation not exceeding 1 ft above MHHW, or the maximum reference elevation of adjacent Rush Landing fringing high marsh (whichever is higher).
o Cover recontoured levee with peat/mud "topsoils" excavated from weed free borrow pits in marsh plain.
o Grade out levee thickets of Himalayan blackberry, placing spoils on the inboard side of the levees to widen the side slopes. The spoils should be placed at elevations such that blackberry roots/stems are completely submerged by daily tides (below MHHW) after restoration.
o Remove Phragmites place as backfill in peat/mud borrow pits to submerge weed residue.
o Salinize soils on the recontoured levee by irrigating with brackish water during first year post-construction and revegetate with native vegetation.
· Expand pond/SAV areas within the marsh by mowing or macerating (using amphibious weed removal equipment) portions of the existing tule/cattail/bulrush marsh bordering the ponds at the mouth of the Suisun Hill Hollow drainage and the SE corner of Goat Island Marsh. The mowing/maceration will help to reduce the regeneration of tall emergent brackish marsh in these areas following tidal restoration.
Public Access & Environmental Education Features
This project element aims to enhance the educational experience of visitors to Rush Ranch by constructing an interpretive nature trail between the ranch headquarters and the proposed Goat Island Marsh restoration site. The interpretive nature trail is intended to provide high volume, low impact visitor access to the Goat Island Marsh restoration site and associated high marsh - grassland ecotone and ameliorate closure of a one mile portion of levee trail around Goat Island Marsh (Section 4.1).
Public access features include:
· Nature Trail. Realignment of existing fence lines and footpaths between the preserve headquarters and Goat Island Marsh.
· Boardwalks. Construction of a boardwalk, footbridge, wildlife viewing blind, water quality sampling station, interpretive signs, and gathering areas to facilitate instructional use and provide a safe and attractive visitor experience.
· Interpretive Signage. Interpretive signs describing ecological features of the tidal marsh and high marsh- terrestrial ecotone, habitat restoration objectives and actions, and describing the importance of tidal wetlands conservation in Suisun Marsh and the San Francisco Bay Estuary.
If the project does not occur, the site will continue to function at a low ecological level, with limited benefits to endangered species. The levee will deteriorate and the Marsh Trail will be closed. Eventually, unplanned inundation of the wetland will occur, and the opportunity for to establish site elevations suitable for sediment accretion and resilience in the face of climate change will be lost, resulting in a low-functioning tidal marsh with serious weed problems and no public access 20-30 years down the road.
i. Water Supply (conservation, recycled water, groundwater recharge, surface storage, etc.)
ii. Water Quality
80 acres of stagnant muted marsh will be converted to daily tidal flushing over restored marsh habitat.
iii. Flood and Stormwater Management
Flood hazard on 1 mile of public access trail will be eliminated and replaced with a 0.5 mile interpretive nature trail and boardwalk providing a safer, more informative and higher quality user experience.
iv. Resource Stewardship (watershed management, habitat protection and restoration, recreation, open space, etc.)
80 acres of tidal marsh and high marsh terrestrial habitat will be restroed to benefit Suisun thistle (Cirsium hydrophilum var. hydrophilum), soft bird’s beak (Cordylanthus mollis ssp mollis), salt marsh harvest mouse (Reithrodontomys raviventris), CA clapper rail (Rallus longirostris obsoletus), black rail (Laterallus jamaicensis), delta smelt (Hypomesus transpacificus) and longfin smelt (Spirinchus thaleichthys), and other rare and special status species.