Water Apron

a large section of a reinforced riverbed downstream from the spillway; intended to take the force of the flow and to dissipate the energy of the water passing over the spillway, as well as to protect the riverbed from dangerous erosion. Depending on the type of dam and the nature of the soil to be protected, a water apron may be a concrete slab or a wooden (cribwork or piling) floor (in wooden dams). Stilling pools, auxiliary dams, and stream energy baffles are often placed within the area of the water apron to increase dissipation of the surplus kinetic energy of the stream. The construction of a stilling pool in conjunction with an auxiliary dam and baffles is more efficient and economical.