Wetlands are areas that are periodically saturated with water. Commonly referred to as marshes, swamps, or bogs these areas are a transition between terrestrial and aquatic systems. Wetlands serve very important functions. They provide habitat for wildlife, assist in flood and erosion control, and recharge groundwater and stream flow. Their vegetation filters out impurities in water and traps sediment that could choke out aquatic life in streams. To qualify as a wetland under federal regulations, a wetland must meet three criteria. First, it must have hydric soils. Soils exhibit hydric characteristics when they are waterlogged for at least one to two weeks per year. Second, more than 50% of the area's plants must be designated as wetland plants. Third, it must possess signs of hydrology. Hydrology signs include drift lines, flow patterns, or debris in trees as a result of flooding. The presence of water within 18" of the soil surface is also a indicator of hydrology. At Catoctin there are 18 wetland areas covering nearly 143 acres of the park. Most of these wetlands are located alongside, or in close proximity to, streams.