Most people think of a wetland as a marshy area near a lake, ocean or river. They believe that urban wetlands are merely the result of flooding or poorly designed drainage systems. They can also be thought of as a nuisance because of the number of mosquitos present in the low levels of water. A wetland is defined as a land area that is saturated with water (permanently or seasonally) such that it takes on the characteristics of a distinct ecosystem. The water table stands at or near the land surface for a long enough period each year to support aquatic plants. Anaerobic plants can survive in this environment, common examples include cattails, sedges and water-lilies.
As run-off enters the wetland, sediment drops out and settles to the wetland floor. The geology of the area explains why a wetland is found in a particular place. Generally, there are two ways in which the geology contributes to wetlands forming: 1. Downward erosion may be stopped by a geological obstruction, resulting in extensive flat areas where water accumulates. This obstruction often consists of very hard erosion resistant rock, such as dolerite, but alluvial soil deposits may also act as an obstruction. 2. Impervious material close to the surface forces groundwater movement very close to or onto the soil surface discharging groundwater. Impervious material can be natural (granite) or man made (asphalt or concrete).
The water found in wetlands can be freshwater, brackish, or saltwater. They can be naturally occurring or constructed. Constructed wetlands can be used to treat municipal and industrial wastewater as well as stormwater runoff. Microorganisms thrive in this environment, absorbing excess nutrients, leaving cleaner water to enter the areas below the wetland. Wetlands can also help with flood control. In a time of global warming, excessive air and water pollution, animal extinctions, and urban sprawl, scientists are looking for new solutions to old problems. Constructed wetlands are one solution to these problems.
The geology of the surrounding area impacts this valley. Found between Walden's Ridge and the smaller Godsey Ridge, the nearby creek receives runoff from both. Fast-moving water erodes soil and rock, carrying them down the ridges. Once in the valley the water flow slows allowing the soil, or sediment, it carries to fall to the bottom of the water channel. This process results in the formation of sedimentary rock (see nearby creek bed). Sedimentary rock in this wetland would not impede the flow of water.
For more information www.water.epa.gov/type/wetlands/index.cfm http://www.defenders.org/wetlands/basic-facts http://geography.about.com/od/physicalgeography/a/wetlands.htm
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