During the rainy season, subsurface hydraulic connections and overbank flow from the stream during flooding events are also primary sources. At base water levels, surface water in the wetland are stabilized at or below the elevation of outlets or water control structures and are isolated from the stream. During flooding events, surface flow from tributaries may merge with streamflow as the tributaries deliver water through the wetland to the stream and when the stream overtops its banks during extreme events. The inlet and outlet are the stream channel or culverts containing the stream channel leading into or out of the wetland. Primary water source is the stream channel.
Unidirectional surface flows dominate most of the year.
At low water, water levels are regulated by the water-control structure or edge of the excavation. This prevents surface waters from exiting the wetland downstream through the stream channel and maintains standing water within the wetland, which promotes stagnant conditions. Depression has been formed through excavation on the hillside or at its base. A berm may be placed on the lower edge of the depression to impound water. Closed contours allow accumulation of surface waters and maintenance of ponded conditions.