definition
strict definition
arch dam
A dam curved toward the upstream side so that arch action helps resist the pressure of the water behind it.
An arch dam is a barrier in a flowing water channel which is bowed with the convex side facing upstream. The curved form allows it to be built with less material than a gravity dam or embankment dam.
The upstream curve transfers much of the water load toward the abutments through compression. The curved form therefore contributes directly to resistance against the water pressure.
A gravity dam relies primarily on its mass. An arch-gravity dam combines a curved form with substantial mass.