Induces horizontal forces on submerged portion.

• A. Water Current
• B. Thermal Stresses
• C. Seismic Loads
• D. Deformation Stresses

Answer: (A)

Water moving past a submerged portion creates horizontal loading because the flowing water exerts drag on the surface and, on vertical faces, a horizontal hydrostatic component. The current pushes against the submerged surface, producing a force along the flow direction; its magnitude grows with flow speed and the surface area, and, for a vertical wall, the hydrostatic pressure (p = ρ g h) integrates to a horizontal resultant that increases with depth. In design, this hydrodynamic force is a primary consideration for the stability and integrity of submerged members such as piers and abutments.

Thermal stresses come from temperature changes causing expansion or contraction and create internal stresses rather than a direct environmental horizontal load on submerged parts. Seismic loads arise from ground motion and can induce horizontal forces overall, but they are not the specific horizontal loading produced by water flow on submerged surfaces. Deformation stresses are internal stresses due to deformation under any load, not the external horizontal push from the flowing water.