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Waterco Datrys were commissioned by Rhondda Cynon Taf County Borough Council (RCTCBC) to develop an Outline Business Case (OBC) for flood risk management in Trehafod, Wales. The village has suffered repeated flooding, most notably during Storm Dennis in February 2020, which affected over 68 properties and key infrastructure.
The OBC follows Welsh Government guidance and uses a Five Case Model to assess strategic, economic, commercial, financial, and management aspects of potential flood alleviation measures.
A comprehensive surface water hydraulic model was developed to understand flood mechanisms, supported by site walkovers, stakeholder workshops, and environmental assessments.
A long list of 15 options was qualitatively assessed for constructability, cost, environmental impact, and alignment with investment objectives. This process, involving RCTCBC and Natural Resources Wales, led to a short list of five options for detailed evaluation.
Hydraulic modelling identified upgrading the DCWW surface water pumping station on Trehafod Road to a 2500 l/s capacity as the preferred solution.
This option offers the greatest reduction in flood risk and economic viability, with a benefit-cost ratio (BCR) of 1.12. Other options, including natural flood management and culvert separation, were discounted due to limited impact.
The recommended solution will significantly reduce flood risk for Trehafod’s residents and infrastructure.
Further work at Full Business Case stage will refine costs, address technical limitations, and explore property-level protection to maximise resilience. The project aims to deliver sustainable, adaptive flood protection while engaging the local community and stakeholders throughout.
Our Work
