The Council has now published all five Section 19 flood investigation reports relating to Storm Bert in November 2024 – focusing on impacted locations in the communities of Aberaman, Pontypridd, Nantgarw, Porth and Treherbert.
Under the Flood and Water Management Act 2010 (Section 19), the Council, as the Lead Local Flood Authority (LLFA), is required to investigate significant flood events and publish its findings. These reports must identify which Risk Management Authorities (RMAs) have relevant responsibilities, note the functions that each authority has exercised to date, and outline what they propose to do in the future to manage the risk of flooding.
The Council is responsible for managing the risk from surface water, ordinary watercourses and groundwater sources. Main river flooding is the responsibility of Natural Resources Wales (NRW), and sewer flooding is managed by Dŵr Cymru Welsh Water.
Storm Bert was an extreme rainfall event that brought record-breaking rainfall and river levels across Rhondda Cynon Taf on November 23-24, 2024. An initial Overview Report published by the Council in March 2025 summarised and analysed the storm’s impacts, which resulted in internal flooding to 438 properties and flooded rail and road networks, town centres and business parks.
The report also set out the future programme of work, including producing Section 19 reports for five impacted locations – Cardiff Road in Aberaman; Pontypridd Town Centre; Oxford Street in Nantgarw; Britannia Street in Porth; and Abertonllwyd Street, Dunraven Street and Hill Street in Treherbert. The Council has now completed the publication of these five respective reports.
Councillor Andrew Morgan OBE, Leader of Rhondda Cynon Taf Council and Cabinet Member for Infrastructure and Investment, said: “As the Lead Local Flood Authority, the Council has completed its statutory duty to publish Section 19 reports for five communities impacted by flooding in Storm Bert. These are factual, publicly-available documents compiled using evidence from several sources. They report on the functions that relevant Risk Management Authorities have completed, and also note what they intend to do in the future.
“Residents can be assured that flood alleviation absolutely remains a priority investment area, to target sources of flooding that the Council is responsible for – namely surface water, ordinary watercourses and groundwater flooding.
“Since Storm Dennis in 2020, more than £100 million has been spent on repairs and upgrading a further 100 watercourses, to increase resilience at targeted locations. Four years on in Storm Bert, we believe this investment helped reduce flood risk to 2,200 properties. But, while Storm Bert highlighted our important progress to date, it also reminded us there’s still lots more to do – with intense storms becoming much more common with climate change.
“We continue to work with Welsh Government to secure important funding, with the Council providing match funding across several key programmes. In 2025/26, £4.52 million is secured across the Flood and Coastal Erosion Risk Management and Small Scale Works Grant programmes, plus £1.5 million via the Resilient Roads Fund – with work currently ongoing in our communities.
“I’d also like to thank members of the public who responded to our call for help in March and April this year, to share accounts, photos, and videos from Storm Bert. This evidence helped us to understand what happened and how flooding was caused, as well as establishing what needs to happen next.”
Findings of the five Section 19 flood investigation reports for Storm Bert are summarised below. They were informed via inspections by RCT’s Flood Risk Management team in the days following the storm, information from residents, businesses, RCT’s Public Health and Protection team, RCT’s Highway and Streetcare Depot, and NRW and Welsh Water in instances where applicable.
Cardiff Road, Aberaman (Flood Investigation Area RCT 02)
Storm Bert resulted in 29 homes and a non-residential property being flooded internally, plus significant highway flooding. The primary cause was significant overland runoff generated from the steep hillsides above Aberaman, draining to lower ground via ordinary watercourses. Many of these were overwhelmed with water and overtopped. Surcharging of various combined sewer assets, as well as local surface water accumulation, were also found to have contributed.
As the Risk Management Authority for ordinary watercourse, surface water and groundwater, the Council has undertaken 14 actions and proposes a further six, in relation to the flooding that occurred. Welsh Water is the Risk Management Authority for sewer flooding, and has proposed two future actions. Details about these are included in the full report.
Pontypridd (Flood Investigation Area RCT 08)
The storm resulted in internal flooding to 23 homes and 39 non-residential properties, significant highway flooding, and flooding to the National Lido of Wales. The primary sources of flooding were the River Taff exceeding its channel capacity, as well as the surcharging of various combined sewer assets. The River Rhondda was also a contributing source of flooding at Mill Street.
River level data from NRW’s monitoring stations at Pontypridd and Trehafod show that both rivers were almost four times their typical levels in Storm Bert. This limited the combined sewer network’s ability to manage flows, resulting in an overload that led to various drainage assets surcharging and causing flooding. Water seeping into the foundations of homes and businesses, plus localised surface water accumulation, were also identified as flooding sources.
As the Risk Management Authority for main river flooding, NRW has proposed six actions going forward – while Welsh Water has identified seven actions relating to sewer flooding, and the Council as the LLFA and the Highway Authority has identified seven further actions to manage local sources of flooding. The four Risk Management Authority’s proposals are included within the full report.
Oxford Street, Nantgarw (Flood Investigation Area RCT 12)
The storm saw flooding to 18 homes and three non-residential properties, plus significant highway flooding. The main source was found to be the River Taff overtopping its banks at the location of a previously-removed service crossing.
NRW river level data from its Upper Boat monitoring station revealed the river was more than four times its typical level in Storm Bert (5.07 metres) – only 0.42 metres lower than its highest-ever recorded level. Highway surface water accumulation also exacerbated the flooding, caused by factors like river flows entering surface water drainage systems, and the sheer intensity of rainfall.
With responsibility for main river flooding, NRW proposes four actions for the future, while the Council as the LLFA and the Highway Authority has also put forward four actions to manage surface water flooding. These are described within the full report.
Britannia Street, Porth (Flood Investigation Area RCT 17)
Storm Bert resulted in flooding to 24 homes, along with significant flooding to the highway. The report establishes that the primary source of flooding was the River Rhondda overtopping its southern riverbank at several locations.
Data from NRW’s Trehafod monitoring station showed the river level at more than three metres higher than its typical level (3.6 metres) – just 0.36 metres lower than the highest ever recorded. Flows from a manhole associated with the ordinary watercourse at Coedcae Road contributed to main river flooding at Brook Street, caused by obstructing debris. Surface water accumulation on the highway exacerbated the situation, caused by factors like main river flows entering surface water drainage systems, and the sheer intensity of rainfall.
As the Risk Management Authority for main river flooding, NRW has proposed three future actions, while the Council as the LLFA has proposed three actions for ordinary watercourses and surface water. The Section 19 report describes these actions in full.
Abertonllwyd Street, Treherbert (Flood Investigation Area RCT 25)
The storm saw internal flooding to 37 homes and two non-residential properties, plus significant highway flooding. The main source was overland runoff that was generated from the steep hillsides above Treherbert, draining to lower ground via ordinary watercourses. Many of these became overwhelmed and overtopped. Local accumulation of surface water was also a contributing flood source, resulting from intense rainfall and overwhelmed infrastructure.
The Council is the identified Risk Management Authority for the ordinary watercourse and surface water flooding that occurred at this location. It has undertaken 14 actions and proposes a further six, listed within the Section 19 report.
Posted on 08/10/2025