Penrhys Road Flood Alleviation Scheme

Scheme Background

The area of Penrhys Road in Ystrad has experienced two significant flooding incidents in recent years, with the primary source of flood risk in the area being associated to ordinary watercourse and surface water sources. The most significant flood event occurred during Storm Dennis in February 2020 which resulted in internal flooding to 14 residential properties and 1 business across Penrhys Road.

The flooding is localised to the area and stems from issues related to the hydraulic capacity (ability to manage flow of water during heavy rain and storm events) and susceptibility to debris accumulation causing blockages within the culverted watercourse network coveying through the area. The proposed flood alleviation scheme aims to mitigate these risks by focusing on the Penrhys Road culvert inlet and associated culverted watercourse network. 

The community of Ystrad is also noted as the 63rd most at risk community for both surface water and ordinary watercourse flood risk in Wales according to the Communities at Risk Register (CaRR) which was developed to provide an objective means of identifying risk and prioritising flood risk management activities at a Wales-wide, community level.

Scheme Objectives

• Reduce risk to life by reducing the number of people exposed to risk of flooding of significant depth and velocity.
• Reduce community disruption by reducing the amount of residential and commercial property exposed to flood risk.
• No detriment to downstream receiving River / Watercourse
• Reduce disruption to critical infrastructure or support the preparation of plans to allow their operation to be maintained.
• Ensure projects are constructed in a sustainable way.
• Deliver a preferred option that works with Natural processes and promotes green infrastructure.
• Improve the resilience of flood risk assets against climate change - Promoting Accessibility and Low Maintenance requirements.

Proposed Scheme Description

The project’s goal is to design a flood alleviation scheme that improves the resilience of the ordinary watercourse network, reducing the likelihood of blockage-related flooding incidents while improving the hydraulic capacity of the network. This scheme aims to reduce the potential for hydraulic and blockage-related flooding events within the Penrhys Road ordinary watercourse that could affect the broader Ystrad community.

This project will involve enhancing the resilience of the Penrhys Road culvert inlet and supporting channels, ensuring accessibility for long-term maintenance programs. The focus is on designing improvements and resilience measures to enhance the watercourse’s capacity to manage debris accumulating whilst still maintaining its overall hydraulic capacity.

Furthermore, the project aims to help maintain the transport route along the ‘B4512 Penrhys Road’ Highway, supporting access for the Penrhys community and connectivity between the Rhondda Fawr and Fach valley by limiting the disruption caused by flood risk.