Arfryn Terrace Flood Alleviation Scheme

Scheme Background

The community of Tylorstown is noted as the 83rd 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.

The area of Afryn Terrace, Tylorstown has been subject to several flooding events in recent years, with the primary source of flood risk in the area considered to be from surface water and ordinary watercourses.

Recent flooding in Tylorstown was caused by heavy rainfall resulting in significant overland runoff being generated from the steep hillslopes above Park Street and entering the existing drainage system which became overwhelmed with water and debris and eventually overtopped, impacting several properties and roads on its course of flow. 

The most recent events, which occurred in May 2021 and January 2023, caused internal flooding to 22 residential properties. Climate change is expected to increase the frequency and intensity of storm events, and subsequently the risk of such flooding in the area.

Since these events, the Council has implemented small-scale drainage improvements in the area which include upgrades to the Park Street open channel and piped highway drainage network with the aim of improving sediment control from the upper catchment and improving inlet capacity along park street. Concrete kerb check dams were installed along the length of the open channel and additional high-capacity gully gratings were installed at low spots along Park Street however these small-scale interventions are seen as short-term solutions whilst the wider FAS program is delivered.

Proposed 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
• Improve community resilience to flood events and climate change promoting sustainability and wellbeing.
• Deliver a preferred option that works with natural processes and promotes green infrastructure.
• Enhance local biodiversity and support the resilience of ecosystems services.
• Improve the resilience of flood risk assets against climate change - Promoting Accessibility and Low Maintenance requirements.
• Reduce the impact of climate change.
• Improve Community Wellbeing through the enhancement of local amenity.

Proposed Scheme Description

This project is intended as a catchment-based approach to manage the risk of surface water and ordinary watercourse flooding to the community of Tylorstown, and aims to primarily benefit the residents of Afryn Terrace, Tylorstown as well as providing a reduction in flood risk to residents in Gwernllwyn Terrace also.

The flood alleviation scheme will target the upper catchment, ordinary watercourse infrastructure (open channel and culvert networks) and overland flood routes in the area to provide increased flood resilience by reducing the short, medium, and long-term risk of blockage and hydraulic overload to the existing network. The aim is to provide a 1 in 100 year plus climate change standard of protection to the community of Arfryn Terrace, which will also compliment the advanced works undertaken to date.

Wider benefits include maintaining the community’s significant transport route, specifically Park Street and A4233 East Road, which facilitates the principal highway that connects the communities of Ferndale/Maerdy with Tylorstown and lower Rhondda Valley Fach valley.

To date, RCT Council alongside appointed consultants JBA Consulting, have prepared a Business Justification Case (BJC), in line with the Welsh Government FCERM Business Case Guidance, which involved extensive screening and analysis of various options to address the flood risk in Tylorstown, resulting in the identification of a preferred option for further development.

The preferred option includes a mix of hillslope and channel interventions alongside highway drainage capacity upgrades to improve the conveyance of surface water to existing drainage infrastructure.

Public engagement with the relevant stakeholders will be undertaken as part of the next stage of the project which will be the presentation of the Full Business Case to Welsh Government and into Detailed design phase.