We know that water exerts a pressure on the wall and this thrust is calculated by using the following formula
P = ½Yo H2
where H = height of water above bottom of wall, ft (m)
Yo= unit weight of water.
Unit of water is 62.4 lb/ft3 1001g/m for freshwater and 64 lb/ft3 or 1026.7 kg/m3 for saltwater.
The thrust applied by water is considered to be acting at a distance of H/3 from the bottom of the retaining wall. The pressure distribution is triangular and has the maximum pressure of 2P/H at the bottom of the wall.