Cefnpennar Road culvert network provided inadequate standards of protection in free-flowing and blockage conditions why? Years of lack of investment by Rhondda Cynon Taf Council?

The council allowed development on the Cwmbach floodplain and this is the result when all that water from the mountains reaches the floodplain, no train service factory units flooded Asda flooded, how much of this flooding could have been avoided?

Under Section 19 of the Flood and Water Management Act 2010, the Council has published its thirteenth flood investigation report following Storm Dennis. The latest report focuses on the causes of flooding in Cwmbach.

As the Lead Local Flood Authority, the Council must provide a factual account of what happened in each significant flood event. The unprecedented weather of Storm Dennis (February 15-16, 2020) brought widespread flooding across Rhondda Cynon Taf, and following an initial investigation of 28 affected areas the Council will publish of total of 19 reports relating to specific communities.

The Council has published reports focusing on Trehafod (April 2022), Ynyshir (March 2022), Treorchy (February 2022), Hirwaun, Nantgarw, Pontypridd, Treforest, Glyntaff and Taffs Well (January 2022). They followed publications for Treherbert, Cilfynydd, Pentre, and an Overview Report for Rhondda Cynon Taf, in 2021. All of these reports are available to view on the Council website.

Each Section 19 report identifies the Risk Management Authorities (RMAs), the functions they have exercised and the actions they propose in the future. They are informed by Flood Risk Management Team inspections made after the storm – and information collated from residents, the Council’s Public Health Team, Natural Resources Wales (NRW) and Dwr Cymru Welsh Water.

The latest report on Friday, April 22, for Cwmbach in the Cynon Valley (Flood Investigation Area RCT 03), notes that extreme rainfall in Storm Dennis saw internal flooding to 34 properties – including 18 commercial properties.

The report is available to view in full on the Council’s website, here.

The report for Cwmbach establishes that, from the evidence gathered, the primary source of flooding was as a result of significant overland runoff being generated from the steep hillsides above the village. The rainwater then drained to lower ground via a series of ordinary watercourses – many of which became overwhelmed with water and debris, and eventually overtopped.

The report adds that, following review, the culverted infrastructure associated with the Cefnpennar Road culvert network provided inadequate standards of protection in free-flowing and blockage conditions. The remaining three culvert networks identified as sources of flooding provided adequate protection in free-flowing conditions. However, despite having sufficient capacity to manage expected flows, these three networks were observed to be in a poor condition and saw their capacities significantly reduced by debris blockages.

The Council, as Lead Local Flood Authority and Land Drainage Authority, is the RMA responsible managing ordinary watercourse and surface water flooding. In response to the flooding in Cwmbach, the Council has undertaken 15 actions and proposes a further seven. Some of the completed actions have included clearance of culvert inlet structures – and survey work, cleansing and jetting to more than 2,400-metres of culverted watercourse and highway infrastructure in the local area.

The Council has also led on the development of a multi-agency control room, linked to its Contact Centre, to ensure a coordinated response in future flood events – and has initiated an interim Property Flood Resistance project offering expandable flood gates to properties deemed at high risk of flooding.

It will also look to better understand the catchment above Cwmbach through the development of a Strategic Outline Business Case – which will provide recommendations for suitable management mechanisms to mitigate the wider risk of ordinary watercourse, surface water and groundwater flooding locally.

NRW, as the RMA responsible for managing the river flooding in Cwmbach during Storm Dennis, has commissioned a Cynon Flood Modelling Study. The outcomes of this study will include an assessment of the potential flood risk management options. NRW has also carried out a waterway clearance of the ‘Cwmbach Ditch’ which was identified as a source of flooding to one property.

It has also developed recommendations and a detailed action plan to address improvement areas for future storm events, including the performance of the NRW Flood Warning Service Review and incident management response.

The report concludes that Storm Dennis was an extreme event, and it is unlikely that flooding could be prevented entirely in a similar event. It adds that RMAs satisfactorily carried out their functions in response to the flooding, but further measures to improve preparedness have been proposed by all RMAs.

Roger Waters, Rhondda Cynon Taf Council Director, Frontline Services, said: “The Council has now published 13 flood investigation reports following Storm Dennis, which is a requirement of the Lead Local Flood Authority under Section 19 of the Flood and Water Management Act 2010. Each report identifies Risk Management Authorities and notes their actions since the flood event – as well as the actions that they propose to undertake in the future.

“Each report is a factual document which is fully-accessible for members of the public, published on the Council’s website. Officers continue to work towards publishing 19 reports in total, focusing on specific communities – with the final six being progressed. The latest publication in relation to Cwmbach has concluded that all RMAs undertook their responsibilities in a satisfactory way, and have put forward further measures to improve future preparedness.”

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