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[[Image:LeakyDam.jpg|thumb|right|350px|'''Leaky dam.''' Partners voor Water (2009). Re-hydrating the earth by sustainable, small-scale sub-surface water retention techniques, Vietnam.]]

A floodwater harvesting technique, these are permeable structures built across seasonal riverbeds which retain flash flood water that has a high silt load. The idea is to retain the high-energy floods and stimulate settlement of suspended sediment behind the dam. Water with a lower sediment load is then available to leak through the dam and infiltrate the downstream riverbed which is not blocked by sediment deposits. They have been proven to be able to recharge local aquifers. Leaky dams are excellent in semi-arid areas since they greatly reduce evaporation, in regards to storing water.