National Trust–United Utilities leaky dams: runoff control lessons for drainage engineers
Reviewed by Joe Ashwell

First reported on New Civil Engineer
30 Second Briefing
National Trust and United Utilities are installing a series of timber “leaky dams” on moorland and farmland above the Stubbins Estate in Lancashire in a two‑year natural flood management programme to slow runoff into the River Irwell. The structures are designed to back up high flows in small headwater channels while allowing baseflow to pass, temporarily storing stormwater on the floodplain and in upstream depressions. For civil and drainage engineers, the scheme signals continued deployment of low‑cost, nature‑based attenuation measures alongside conventional hard‑engineered defences in upland catchments.
Technical Brief
- Safety management must address working in steep, wet channels with rapidly changing flow conditions during storms.
- Asset owners will need inspection and maintenance regimes for timber decay, blockage, and post‑storm damage.
Our Take
In our database, United Utilities’ recent £30M retrofit of sustainable drainage in Liverpool and the £6M stormwater tank in St Helens show the utility pairing hard infrastructure with nature‑based measures like the Stubbins Estate leaky dams to manage peak flows across the North West catchments.
The two‑year natural flood management programme at the River Irwell aligns with United Utilities’ wider landscape‑scale work restoring peatlands and woodlands across its North West estate, suggesting the company is treating upstream land management as a core flood and water‑quality control tool rather than a peripheral CSR activity.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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