text: Many check dams tend to form stream pools. Under low-flow circumstances, water either infiltrates into the ground, evaporates, or seeps through or under the dam. Under high flow – flood – conditions, water flows over or through the structure. Coarse and medium-grained sediment from runoff tends to be deposited behind check dams, while finer grains flow through. Floating garbage is also trapped by check dams, increasing their effectiveness as water quality control measures.