USDA Wetland Classifications

Riverine

• Riverine wetlands are generally associated with stream channels. The water source tends to be overflow from the banks of the stream or subsurface connections between stream banks and wetlands, where stream water flows underground to the wetlands. Sometimes a riverine wetland may be formed on floodplains that have poor drainage and therefore retain water longer. Riverine wetlands do not necessarily require constant flow in the adjacent stream channel, as infrequent water inputs may be enough to sustain them.

Depressional and Slope

• As the name implies, depressional wetlands occur in dips in the landscape. Local water flows and collects in the low spot. Depressional wetlands tend to be fed by precipitation and ground water discharge. They can have water flowing through them at times, or they can be completely enclosed and only lose water to evaporation. Slope wetlands are similar. They occur at the end of sloping land, but do not hold the water because they lack closed landscape contours. Therefore, water flow tends to be unidirectional.

Mineral Soil Flats and Organic Soil Flats

• Mineral soil flats can occur on old lake bottoms or in topographic situations in which the only water input is from precipitation. No ground water flow or discharge is associated with mineral soil flats. They tend to have poor drainage and only lose water from evapotranspiration. Organic soil flats are extensive peatlands. Like mineral soil flats, they only receive water from precipitation, but they differ because of their significant accrual of organic material.

Esturarine Fringe and Lacustrine Fringe

• Estuarine fringe wetlands occur along the coast and estuaries. As a result, they are dominated by tides. They are seldom dry, because of the consistency of the tide. They collect organic material along the higher elevations of the fringe, where flooding is less frequent. Lacustrine fringe wetlands can be found along lakes. Lakes flood into adjacent wetlands as a means to control their water tables. Sometimes, lacustrine fringes are floating mats that are attached to a land surface.