Wetlands, along with floodplains and shorelines, are critical environmental areas. Wetlands are saturated lowland areas (e.g. marshes and swamps) that have distinctive soils and ecology. Wetland areas filter flowing water, hold flood water, and release water slowly into surrounding drier land. Traditionally, wetlands have been regarded as undesirable, because they cannot be farmed or developed. Many of the wetlands and marshes in the Huron River Watershed have been dredged, drained, and filled. This has occurred without an awareness that these actions could have long-term consequences for hydrological systems, water quality, and wildlife. To date, the Huron River has lost an estimated two-thirds of its wetlands to agricultural, industrial and residential development. Wetland protection, restoration, and management are, and will continue to be, environmentally critical in the upper and middle sections of the watershed.
Wetlands perform several functions that are essential to environmental health.
Pollution Control. A major function of wetlands is water quality protection. Wetlands function as living filters by retaining or removing polluting nutrients and sediments from surface and groundwater. They do this in four ways: (1) uptake by plant life; (2) absorption into sediment; (3) deposition of organic material; (4) precipitation of chemicals. Nutrient chemicals such as phosphorus are necessary for plant growth, but are also a classic example of the harm done by “too much of a good thing.” Excess nutrients such as phosphorus and nitrogen can damage aquatic ecosystems by promoting an undesirable increase in algae and aquatic plant growth. The result is water reminiscent of pea soup, depleted levels of dissolved oxygen, weed-choked and rapidly aging lakes (a process also referred to as eutrophication).
Sediment Control. As sediment-laden water flows through a wetland area from the surrounding watershed, the sediments are deposited into the wetland. This reduces the formation of silt in lakes, rivers, and streams. Wetland vegetation and flat topography slow the water’s flow and increase the deposition rate of silt and organic matter. Heavy metals and toxic chemicals often attach to the sediment particles found in surface water runoff. Wetlands can trap these man-made pollutants and remove them from the water column. However, when the natural ability of wetlands to function as filters is overstressed, the wetland and its functions can be destroyed and the wetland itself can become a source of pollution.
Erosion Control. In their natural state, wetlands function as an inhibitor or barrier to erosion. The root systems of wetland plants stabilize soil at the water’s edge and enhance soil accumulation at the shoreline. Wetland vegetation along shorelines also reduces erosion by damping down wave action and slowing the speed of the water’s current.
Flood Prevention. Wetlands act as a hydrologic sponge, temporarily storing flood waters and releasing them slowly, preventing flood peaks and protecting downstream property from flood damage. Wetlands and floodplains often form natural floodways that convey flood waters from upland to downstream areas. This wetland function has become increasingly important in urban areas where development has increased the rate and volume of stormwater runoff.