The total thrust from water retained behind a wall is

P = ½ g_o H²

where H = height of water above bottom of wall, ft (m); and
g_o= unit weight of water, lb/ft³ (62.4 lb/ft³ (1001g/m) for freshwater and 64 lb/ft³ (1026.7 kg/m³) for saltwater)

The thrust is applied at a point H/3 above the bottom of the wall, and the pressure distribution is triangular, with the maximum pressure of 2P / H occurring at the bottom of the wall. Regardless of the slope of the surface behind the wall, the thrust from water is always horizontal.