Source: EPA


caption Tidal marsh along the Edisto River, South Carolina.

Marshes are defined as wetlands frequently or continually inundated with water, characterized by emergent soft-stemmed vegetation adapted to saturated soil conditions. There are many different kinds of marshes, ranging from the prairie potholes to the Everglades, coastal to inland, freshwater to saltwater. All types receive most of their water from surface water, and many marshes are also fed by groundwater. Nutrients are plentiful and the pH is usually neutral leading to an abundance of plant and animal life. For the purposes of this publication, we have divided marshes into two primary categories: tidal and non-tidal.

Functions & Values

caption Common Cattail (Typha latifolia) is a freshwater and estuarine marsh species.

Marshes recharge groundwater supplies and moderate streamflow by providing water to streams. This is an especially important function during periods of drought. The presence of marshes in a watershed helps to reduce damage caused by floods by slowing and storing floodwater. As water moves slowly through a marsh, sediment and other pollutants settle to the substrate, or floor of the marsh. Marsh vegetation and microorganisms also use excess nutrients for growth that can otherwise pollute surface water such as nitrogen and phosphorus from fertilizers. This wetland type is very important to preserving the quality of surface waters. In fact, marshes are so good at cleaning polluted waters that people are now building replicas of this wetland type to treat wastewater from farms, parking lots, and small sewage plants.

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Environmental Protection Agency. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Environmental Protection Agency should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.



(2008). Marsh. Retrieved from


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