Tidal Marsh Restoration

Type of Development

Restoration

Topography

Baylands

Longevity

Long Term

Environment

Natural Habitat

Maintenance

Low

Cost

Dependent on scale.

Overview

Tidal marsh restoration is the restoration, maintenance, and protection of tidal marshes and tidal flats through added sediment and planted vegetation. The restoration involves a multi-step process of planting native and salient (salt-water friendly) plants and adding sediment to restore tides and connect marshes to adjacent environments, including the greater watershed. First, planting native, salient plants accelerates the colonization of healthy plants, reduces erosion from tides through wave dampening, and encourages organisms to live, grow, and flourish within the ecosystem. Second, adding sediment creates elevated areas to provide high-tide refuge for endangered and native animals as sea levels rise, and also helps to cycle through fundamental nutrients. Third, restoring tidal action to diked baylands restores the tidal marsh ecosystem by reducing stagnant, unfiltered, polluted water.

Illustration of shoreline ecosystem that supports biodiversity, groundwater recharge and cooling impacts.

Function

Tidal marsh restoration elevates land, restores habitats, and dampens wave volume and impact.

Benefit

In addition to sustaining food for habitats, tidal marshes help to manage the strength and velocity of waves through shoaling and the friction of vegetation, dampen storm surges, and protect adjacent infrastructure and habitats from rising seal level. For example, tidal marshes control the erosion of levees, which allows levees and seawalls to be built lower.

Dependency

Hydrologic System

Development Considerations

Hydraulic connections will determine the sediment and water supply. Land ownership is important to keep in mind when finding sites.

Environmental Considerations

Since the salinity of the water will change over time, plants must be salinity resistant. While tidal marshes can act as wave dampeners, factors such as wave size, wavelength, and vegetation characteristics (canopy height, density, stem diameter, and stiffness) can impact the effectiveness of wave dampening. For example, higher waves are dampened better than low waves.

Maintenance Consideration

Within the first few months, maintenance is required to ensure that planted vegetation is rooted and stable. If the planted vegetation is not rooted and stable, there is a need to continue a sediment supply until the ecosystem can sustain itself. While other maintenance is not required, tracking the progress of restored tidal marshes is valuable for future projects. Little to no maintenance is expected after 2 years.

Cost Considerations

Dependent on scale.

Case Studies

South Bay Salt Pond Restoration

This restoration project is the largest tidal restoration project on the west coast. The project is in the midst of restoring over 15,000 acres of industrial salt ponds to natural tidal marshes.

Image of an overlook to the baylands with cultivated areas to the left and marsh lands on the right.

Sonoma Creek Baylands Strategy

The Sonoma Creek Baylands Strategy was created to mitigate flooding events and reintroduce public access to the restored environment. Further benefits are protecting endangered species such as the salt marsh harvest mouse.

Moffett Park Specific Plan Urban Ecology

The Moffett Park Technical Plan lays out a city wide redevelopment of green infrastructure and Nature-Based Strategies that create habitats and natural corridors in order to reduce climate impacts and positively impact the community.

Aerial image of the bay lands and Bair Island

Bair Island Wetlands Restoration

Bair Island in Redwood, CA is three islands in close proximity to each other that have undergone a massive restoration effort by local organizations to transform thousands of acres of salt ponds back into tidal flats.

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