Neglected Culverts Can Cause Major Floods

A culvert that is silted up, blocked by debris or structurally failing can turn a heavy storm into a flood. Water backs up at the inlet, spills overland and finds new routes through roads, properties and railway embankments. Regular inspection and cleaning is the simplest way to reduce that risk.

Why Culverts Block

• Debris: branches, leaves, litter and fly-tipped waste washed down in high flows.
• Silt: gradual deposition that reduces capacity long before a full blockage.
• Screens: trash screens that are not cleared can cause the blockage they were meant to prevent.
• Structural defects: collapse, displaced joints and scour at inlets and outlets.

The Scale of the Risk

The Environment Agency’s national assessment estimates 6.3 million properties in England are in areas at risk of flooding, with 4.6 million of those in areas at risk of flooding from surface water. It also projects that the number at risk could rise to around 8 million by mid-century with climate change. Rainfall is already changing: the Met Office reports the winter half-year for 2016–2025 was 13% wetter than 1961–1990.

When Culverts Fail on Infrastructure

Drainage failure can have severe consequences. At Carmont, Aberdeenshire, on 12 August 2020, a passenger train derailed because it struck debris that had been washed out of a drainage trench; three people died.

Who Is Responsible?

Government guidance says you normally own a watercourse that runs on or under your land, including through an underground pipe or culvert. Landowners, highway authorities, rail operators and estate managers all hold culverts that need managing.

A Practical Maintenance Regime

1. Asset register: locate and record every culvert, inlet, outlet and screen.
2. Risk rating: rank by debris load and consequence of blockage.
3. Inspection: remote CCTV, sonar and pole cameras; see culvert inspections.
4. Cleaning: jetting and tanker recovery of silt and debris; see culvert cleaning.
5. Repair: no-dig lining and patch repairs where defects are found.
6. Storm checks: screen checks before forecast heavy rain and after events.

Frequently Asked Questions

Can a Partial Blockage Cause Flooding?

Yes. Silt and debris reduce capacity, so a culvert that copes in normal flows can surcharge in a storm.

Should Staff Enter Culverts to Clear Them?

Not without a confined space safe system of work. Government guidance for owners says do not go inside a culvert; remote methods should come first. See confined space surveys.

Talk to Us

Civil Connect Subsurface Solutions inspects, cleans and rehabilitates culverts for public and private asset owners, including planned maintenance programmes. Contact us or call 0208 387 5591.