Which method is commonly used to observe underwater scour patterns around foundations without relying on surface visibility?

• A. Underwater inspection
• B. Aerial photography
• C. Ground-penetrating radar from surface
• D. Visual inspection from the bank

Answer: (A)

Direct observation underwater is necessary to see scour around submerged foundations when surface visibility is poor. Underwater inspection, using divers or remotely operated vehicles, provides a direct view of the seabed around piers and foundations, letting you document scour holes, sediment levels, and potential undermining, with measurements or mapping via sonar or photogrammetry. This approach works because the observer is in the submerged environment, not relying on clear surface water. Aerial photography looks from above and cannot reveal underwater scour; surface-based ground-penetrating radar is not effective for observing scour around submerged structures; visual inspection from the bank cannot see beneath the water surface.