Flood arch

A flood arch is a small supplemental arch bridge provided alongside a main bridge.

[1] The space beneath a flood arch is normally dry and often carries a towpath or similar.

In some cases it borders on the shallow edge of a river, but this does not carry substantial flow in normal conditions.

A bridge with multiple arches across a flowing river would instead be termed a viaduct.

This article about a specific type of bridge is a stub.

Bywell Bridge , two of the river spans with a flood arch beyond. The level of flooding can be seen by the driftwood caught above the cutwater
Pant-y-Goitre Bridge with both pierced spandrels and a flood arch