Which term refers to a hydraulic structure typically under fill?

• A. Bridge
• B. Culvert
• C. Pier
• D. Abutment

Answer: (B)

A culvert is a conduit that allows water to pass beneath an embankment or road fill. This makes it a hydraulic structure by its very purpose: to maintain drainage and control flow under structures raised on fill. In practice, roads and railways are often built on fills, so culverts are installed to let streams, runoff, or drainage pass through without eroding the fill or flooding the roadway.

By contrast, a bridge spans a gap to carry traffic; a pier is a vertical support for a bridge, and an abutment is the end support that transfers loads to the ground. None of these are primarily about passing water through under fill, which is why culvert is the correct term.