6.0 – Wetlands, Riparian Areas, and Vegetated Treatment Systems

Wetlands are areas that are inundated or saturated with water and support a prevalence of aquatic vegetation typically adapted for life in saturated soils. Wetlands are also referred to as swamps, marshes, bayous, sloughs, pocosins, bogs, moors, fens, carrs, and dambos. Related, riparian areas are ecosystems along a water body through which energy, materials and water are transferred. It is important to note that the two areas have a continuous ecological function; i.e. impacts to the upland, riparian area of the system will affect any associated depositional wetlands. Wetlands provide a range of ecological functions important to humans such as water storage and groundwater recharge in addition to providing aquatic and terrestrial habitat for many species including many federally listed endangered and threatened species. Wetlands buffer pollutants by providing plenty of organic matter that increases buffering capacity of sediments, by hosting microbes that transform a variety of pollutants, by capturing sediment and by physically attenuating high velocity flows. Wetlands located adjacent to coastal estuaries (estuarine fringe) and large lakes (lacustrine fringe) dissipate high energy storm surges (wind and waves) which can protect lives and property.

Wetlands may be virtually destroyed by construction, filling, or other significant alterations. Historically, significant losses of wetlands have been caused by draining wetlands soils for conversion to croplands and dredging wetland soils for navigation. Spongy wetland soils are compacted by over-grazing and grading. Loss of wetland acreage increases polluted runoff leading to degradation of surface water quality.

Stream channels and associated riparian areas function to transport water, energy and sediment from upland sources within their respective watersheds to depositional areas, typically wetlands, lakes, estuaries, and oceans. Some erosion and deposition is naturally occurring and beneficial to ecosystems, however, excessively high erosion especially of fine-grained sediments and clays into receiving waters can increase sediment oxygen demand and smother aquatic life, physically cover shellfish beds and aquatic vegetation, and fill in riffle pools (important for native fish spawning). Sedimentation (measured by turbidity) of water bodies is a positive feedback loop which further increases water temperature, fostering algae blooms, reducing dissolved oxygen and in extreme cases causes eutrophication. Sediment often contains toxic compounds sorbed onto the soil organic matter. The solubility for many toxic chemicals sorbed onto sediment particles is increased as temperature increases. Therefore, in addition to metabolic stress, increased water temperatures also cause aquatic organisms to suffer from toxic stress. Sedimentation of receiving waters and physical fish passage barriers are typically caused by alterations to stream and river channels or hydromodification. Refer to Section 5 in this Encyclopedia for more information on hydromodification impacts to stream channels and riparian areas.

Riparian forests have been found to contribute to the quality of aquatic habitat by providing cover, bank stability, and a source of organic carbon for microbial processes like denitrification (James et al., 1990; Pinay and Decamps, 1988). Riparian systems, particularly in western regions, have been shown to stabilize the recharge of shallow aquifers in a manner that supports streamflows of longer natural duration (Platts and Jenson, 1990).

Several factors determine the pollutant-removal efficiency of a specific wetland or riparian area, including the following:

  • Frequency and duration of flooding
  • Types of soil
  • Slope of landscape
  • Types of vegetation
  • Balance of nitrogen and carbon
  • Ratio of edge to area for the wetland or riparian area

Vegetated treatment systems (VTS) have been installed in a wide range of settings, including cropland, pastureland, forests, cities, and urbanizing areas, where the systems can perform a complementary function of sediment control and surface water runoff management. VTS can be considered a Low Impact Design (LID) strategy and include management practices such as vegetated filter strips, vegetated buffers, and vegetated swales. VTS take advantage of plants ability to uptake nutrients for the purposes of improving water quality in a process called phytoremediation. Constructed wetlands are considered VTS, however, these areas are not simply vegetated drainages. Constructed wetlands are designed to mimic natural hydrological characteristics found in undisturbed wetland areas so that water quality objectives can be reached or maintained in the receiving waters (if any).

Restoration Activities Sediment (fine) Water Temp Salinity pH D.O. NPK Toxics
Reduction of land disturbance decrease - decrease - decrease - variable increase + decrease - decrease -
Reduction of impervious surface decrease - decrease - none increase + increase + decrease - decrease -
Restore Riparian Vegetation decrease - decrease - decrease - decrease - increase + decrease - decrease -
Restore wetlands decrease - variable variable variable decrease - increase + increase +
Stabilize channel and restore undercut banks decrease - decrease - decrease - decrease - increase + decrease - none
Create drop structures increase + none none variable increase + none decrease -
Re-establish riffle substrate none none none variable increase + none none

Table 1. Potential water quality impacts of selected stream restoration activities within a watershed (Federal Interagency Stream Restoration Working Group, 1998)

Several minor name changes were made to the 2006 edition of the NPS Encyclopedia. Former MM 6A - Protection of Wetlands and Riparian Areas was renamed to Protection and Conservation of Wetlands and Riparian Areas. Former MM 6B - Restoration of Wetlands and Riparian Areas was renamed to Restoration, Rehabilitation, and Mitigation of Wetlands and Riparian Areas.

The links below provide specific information for each of the following management measures.

General Programs

  • Clean Water Act Section 401 Certification Program, RWQCB and SWRCB review projects that require a federal permit under CWA section 404 or that involve dredge or fill activities that may result in a discharge to waters of the United States. This is to ensure that the State’s interests are protected on any federally permitted activity occurring in or adjacent to waters of the State. Detailed information about CWA section 401 in California, including a description of the program, resources, legal background information, proposed projects, and links, are described on the SWRCB Website.
  • EPA’s Wetlands Program encourages and enables others to act effectively in protecting and restoring the nation’s wetlands and associated ecosystems, including shallow open waters and free-flowing streams. In doing so, the program engages in two principal categories of activities–establishing national standards and assisting others to meet them.
  • EPA's National Estuary Program was established by Congress in 1987 to improve the quality of estuaries of national importance. The Clean Water Act Section 320 directs EPA to develop plans for attaining or maintaining water quality in an estuary.
  • US Army Corps of Engineers 404 Program wetlands regulatory program and offers policy and guidance related to wetland management. The site provides links to laws and regulations governing activities that can impact wetlands, policy documents, jurisdictional information, and technical guidance for delineation, management, and mitigation.

General Resources

  • California Coastal Commission’s Local Assistance Program, Links to Wetlands Sites Web page contains Web links related to wetlands management in California and nationally.
  • California Rapid Assessment Method (CRAM) is a standardized, cost-effective tool for assessing the health of wetlands and riparian habitats. CRAM software guides users through assessments that take less than one-half field day to complete. CRAM is applicable to all wetland types. It is designed for assessing ambient conditions within watersheds, regions, and throughout the State. It can also be used to assess the performance of compensatory mitigation projects and restoration projects.
  • California Resources Agency, California Wetlands Information System is a compilation of public and private sector information, including maps, environmental documents, agency roles in wetlands management, restoration and mitigation activities, regulatory permitting, and wetland policies. It is designed to provide comprehensive wetlands information to the general public, the educational community, and government agencies.
  • Center for Watershed Protection Wetlands has assembled a Website as a central source for information on wetland protection information. The site includes articles from the Center’s Wetlands and Watersheds Article Series, Web links, an events calendar, glossary, and other resources.
  • Coastal Conservancy and California Coastal Commission, Southern California Coastal Wetlands Inventory consists of a database of existing information on 41 coastal wetlands that lie between Mexico and Point Conception in northern Santa Barbara County. It provides three types of information for each site: (1) a map of the wetland’s historical extent, (2) a map of recent habitat distributions, and (3) a "profile" that briefly describes ecological conditions and land use and enhancement histories.
  • Kazmierczak, R.F., Jr., Three discussion papers on economic linkages between coastal wetlands and other environmental and recreational goals provides links to several discussion papers that discuss the economic linkages between coastal wetlands and habitat/species protection, hunting and fishing, and water quality.
  • NatureServe Biodiversity Values of Geographically Isolated Wetlands in the United States , this report discusses some of the implications of the 2001 Supreme Court decision SWANCC vs. the U.S. Army Corps of Engineers, which states that some wetlands and other waters that are considered "geographically isolated" from navigable waters do not fall under the jurisdiction of the Clean Water Act. Included in the report is an analysis of wetland ecosystems that can be interpreted to be "geographically isolated" and the types and numbers of at-risk species and plant communities that these habitats support. The full report can be downloaded in PDF format, and several appendices also are available that summarize methodologies and data used in the analysis, including standards for ecological classification, dichotomous keys to and descriptions of geographically isolated wetlands in the U.S., at-risk animal and plan species tied to isolated wetland ecological systems, and area-weighted counts of at-risk species by county, among others.
  • Orange County Coastkeeper is a nonprofit environmental activist organization, is to protect and preserve Orange County’s marine habitat and watershed through education, restoration, and enforcement.
  • Pacific Estuary Research Laboratory offers such resources as water quality-related reports and data, A Manual for Assessing Restored and Natural Coastal Wetlands, and other tools related to wetlands management.
  • Sacramento River Riparian Habitat Program is working to ensure that riparian habitat management along the river addresses the dynamics of the riparian ecosystem and the reality of the local agricultural economy.
  • EcoAtlas provides free public access to information about the location, size, sponsors, habitats, contact persons, and status of wetland restoration, mitigation, creation, and enhancement projects in the San Francisco Bay Area.
  • San Francisco Bay Joint Venture (SFBJV) is a partnership that brings together public and private agencies, conservation groups, development interests, and others seeking to collaborate in restoring wetlands and wildlife habitat specifically within the San Francisco Bay watersheds and along the San Mateo Coast.
  • San Francisco Estuary Institute provides free public access to information about the location, size, sponsors, habitats, contact persons, and status of wetland restoration, mitigation, creation, and enhancement projects in the San Francisco Bay Area.
  • USDA Forest Service, Sierra Nevada Research Center the Aquatic, Riparian and Wetland Ecology Group focuses on the response of populations and communities of aquatic and riparian-associated species to natural and anthropogenic influences, such as introduced exotic species, natural and regulated stream flow regimes, livestock grazing, natural and prescribed fire, and vegetation management.
  • U.S. Geological Survey National Wetlands Research Center (NWRC) develops and disseminates scientific information needed for understanding the ecology and values of wetlands and for managing and restoring wetland habitats and associated plant and animal communities.
  • USEPA National Management Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpoint Source Pollution, this technical guidance and reference document to assist nonpoint source managers and the public in the implementation of nonpoint source pollution management programs. It contains information on the best available, economically achievable means of reducing nonpoint source pollution through the protection and restoration of wetlands and riparian areas, as well as the implementation of vegetated treatment systems. Topics covered include an overview of wetlands, riparian areas, and vegetated treatment systems; techniques for the protection and restoration of wetlands and riparian areas; and management measures for vegetated treatment systems. The appendix includes a list of financial and technical assistance programs, government contacts, and an index of case studies.

Funding Resources


Federal Interagency Stream Restoration Working Group. 1998. Stream Corridor Restoration: Principles, Processes, and Practices.

SWRCB and CCC. 2000. Volume II: California’s Management Measures for Polluted Runoff (CAMMPR). State Water Resources Control Board and the California Coastal Commission, Sacramento, CA.

USEPA. 2001. Chapter 4: Management Measure for Protection of Wetlands and Riparian Areas. In National Management Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpoint Source Pollution (Draft). EPA 841-B-01-001. U.S. Environmental Protection Agency, Washington, DC.

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