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A '''check dam''' is a small, temporary or permanent dam constructed across a drainage ditch, gully, swale, or channel to lower the speed of concentrated flows (like an overflow weir) for a certain design range of storm events. They may be more categorized as a type of floodwater rather than a runoff harvesting technique. A check dam can be built from logs of wood, stone, pea gravel-filled sandbags or bricks and cement. They have been used widely in Kenya and India. These dams can also be made as [[Water Portal / Rainwater Harvesting / Groundwater recharge / Leaky dams | leaky dams]]. Dams that have been built in riverbeds with no coarse sand transport ([[Water Portal / Rainwater Harvesting / Groundwater recharge / Sand dam | Sand dam]]s) may end up being used in this way. These structures are relatively cheap and can last about 2-5 years.