Hydromorphology

Operation to lower water level and increase outflow rates to discharge some of the sediment retained by a dam. A dam release consists in opening the gates, thus limiting the silting of the dam reservoir and the risk of flooding. This operation, although common in the management of harnessed rivers, can have adverse effects on the downstream environment (decrease of oxygen levels in water, obstruction of fish gills by suspended solids, etc.).

Dam with a complex design, which is thin and resistant to the hydraulic pressure by bracing the rocky sides of a valley. These dams are particularly suitable for narrow valleys.

A groundwater impoundment structure built across underground water channels. The underground dams are built in the sub-soil. They store water in geological formations, retain groundwater and require pumping facilities to make water usable.

Structure built for the storage of water for replenishing low water levels or supplying channels.

A rather old dam, made of a block of solid material (concrete or masonry) heavy enough to withstand the water pressure.

A structure built on a watercourse for creating a water reservoir to ensure a constant production of electricity. The impounded water of the reservoir is conveyed by pipes to the power plant.

An embankment, formed of compact earth, built across the bed of a river to create a water reservoir. This is the simplest and oldest type of dam. Its slopes must be soft enough to ensure stability and the earth must be sufficiently impermeable (e.g. clay).

Dam consisting of a succession of solid frames (foldable metal frames) connected by a bridge and each supporting a movable part - the needle - which can be raised or lowered.

A structure intended to ensure a sufficient and relatively horizontal water level to allow navigation. It can be fixed or mobile.