Lower Rhondda Fawr Flood Alleviation Scheme

This page provides details about the proposed works and their significance to the community of Lower Rhondda Fawr.

Scheme Background

To manage flood risk within RCT, the authority has broken the area down into 12 sections, referred to as Strategic Flood Risk Areas. Each area sits within a drainage catchment, designated based on the geography of the area and the local flood history. There are 4 in the Rhondda valley, 4 in the Cynon valley and 4 in the Taf valley. The Lower Rhondda Fawr catchment includes the Rhondda Fawr river and is categorised by steep-sided valleys and urban areas on the valley floor.

Since 2020, the Lower Rhondda Fawr SFRA has been impacted by internal flooding to properties several occasions, including Storm Bert.

The most significant rainfall event, designated by the Met Office as ‘Storm Dennis’, occurred between the 15and 16^th of February 2020. The storm resulted in internal flooding to 1,498 homes and businesses across RCT, of which 22 residential properties and 9 non-residential properties were situated in the Lower Rhondda Fawr SFRA.

More recently, between the 23^rd and 24^th November 2024, a rainfall event designated as ‘Storm Bert’ by the Met Office resulted in internal flooding to a further 11 residential properties and 8 non-residential properties in the Lower Rhondda Fawr SFRA.

The Lower Rhondda Fawr SFRA is noted as an area of high surface water and ordinary watercourse flood risk based on Natural Resources Wales’s Flood Risk Assessment Wales (FRAW) maps. Within the Lower Rhondda Fawr SFRA, there are 6 communities designated by the Welsh Government’s Communities at Risk Register (CaRR) 2024. These communities, and their community flood risk ranking for surface water and ordinary watercourse flooding in Wales (according to the CaRR 2024) are listed below. All 6 communities fall within the top 5% (top 111) of communities at greatest risk of surface water and ordinary watercourse flood risk in Wales.

The council has already delivered several interventions within the SFRA to reduce the risk of flooding whilst the wider program is delivered.

• Clearing and maintenance of culvert inlets and networks.
• Installation of CCVT monitoring and river level gauges on key watercourses.
• Delivery of PFR flood gates to properties impacted by Storm Dennis and Bert.

Proposed Scheme Objectives

In delivering this project the authority will deliver upon 14 of the objectives identified within RCT's Local Flood Risk Management Strategy¹, a summary of which is provided as follows:

1. Reduce distress by decreasing the population exposed to flood risk
2. Reduce risk to life by reducing the number of people exposed to risk of flooding of significant depth and velocity
3. Reduce community disruption by reducing the amount of residential and commercial property exposed to flood risk
4. Reduce disruption to critical infrastructure or support the preparation of plans to allow their operation to be maintained
5. Improve or not detrimentally affect water quality
6. Where possible, improve naturalness – reducing modifications to channels, water bodies and where appropriate, create or enhance natural floodplain storage linked to nature conservation and landscape initiatives
7. Ensure projects are designed and constructed in a sustainable way
8. Maintain, or where possible, improve the status of SACs, SSSIs, SINC and contribute to the RCT biodiversity action plan
9. Explore the potential benefits of reducing flood risk through the use of innovative land management techniques
10. Provide clarity of stakeholder's responsibilities with regard to flooding and, where possible, seek to support stakeholders in carrying out their responsibilities
11. Develop a better understanding of the risks of flooding from surface runoff, groundwater and ordinary watercourses and plan how best to communicate and share information with communities and businesses on all forms of flooding
12. Promote resilience at property/community level
13. Ensure that RCT works in partnership with other Risk Partners and works collaboratively with adjacent authorities
14. Ensure that investment decisions for the implementation of FRM schemes are made on a consistent prioritised basis subject to cost benefit analysis. 

Proposed Scheme Description

This project is intended to establish a Programme Business Case to understand the risks associated to local sources of flood risk (surface water, ordinary water and groundwater flooding) and identify options to manage them, along with potential wider benefits to the community.

The Programme Business Case will:

• Assess risks from surface water, ordinary watercourses and groundwater
• Identify a long list of potential interventions, including engineered solutions and natural flood management approaches
• Evaluate the risks associated with hydraulic capacity, blockages and structural weaknesses in existing infrastructure
• Explore opportunities to work with natural processes, such as upstream storage, habitat creation and land management improvements.
• Consider wider benefits for businesses, transport networks and community wellbeing.  

This programme-level approach ensures that solutions are not only technically effective but also environmentally sustainable, community-focused and aligned with long-term climate resilience. The Scheme development may also be localised to specific locations rather than the whole catchment upon identification of the best options available to manage risk.

Flood Risk Management 

Highways, Transportation and Strategic Projects,
Rhondda Cynon Taff County Borough Council
Floor 2
Llys Cadwyn
Pontypridd

CF37 4TH

Email: FRM@rctcbc.gov.uk