Roath Brook Flood Scheme


Penylan is a central suburb in Cardiff, through which runs Roath Brook. The Roath Brook burst its banks most recently during high river flows in 2007 and 2009 and during high tidal events in 2010 and 2012.Flood risk areas of Roath and Rhymney

Many homes and businesses in the area are at risk of flooding. This is from high river flows, high tides or a combination of both.

The likelihood of flooding will only increase over time, as a rise in sea levels and more frequent and intense heavy rainfall are predicted as a result of climate change.

The Scheme

The Roath Brook Flood Scheme (Phase 1 and 2) was completed in 2018 and reduces the risk of flooding to more than 300 properties to a 1 in 75 chance flood event (1.3% chance of flooding in any given year) from high river flows and a 1 in 150 chance flood event (0.6% chance of flooding in any given year) of high tide levels. 

Improvements have been made at several locations along the brook between Roath Mill Gardens and the River Rhymney at Newport Road (near to the Morrison’s supermarket). The main areas are:

  • Roath Mill Gardens
  • Waterloo Gardens
  • Railway Gardens (The Sandies)

Overview plan

We've built flood walls and embankments in Roath Mill Gardens, Waterloo Gardens and Railway Gardens, and replaced Waterloo Road bridge to increase the brook’s flow capacity. We've softened these hard features with urban landscaping. 

Through continual consultation with local residents, businesses and stakeholders, we listened to the local community who helped us shape the final design, including minimising tree removal and reducing walls across the scheme.

Planning permission was granted for the scheme in April 2016 by Cardiff Council. The details for the planning submission can be viewed online.

Work to address the remaining flood risk

On 24 January 2019, NRW's Board approved our proposal to reassess the final phase of the Roath Brook Flood Scheme (to widen the brook in Roath Brook and Roath Mill Gardens) as a stand-alone project. We based this decision on advice from the Welsh Government, views provided by the campaign group from an independent consultant and no overwhelming support from the affected community.

We completed our re-assessment of the flood risk in March 2020. The re-assessment considered the work already completed downstream and the new footbridge built in Roath Brook Gardens by Cardiff Council. The footbridge was constructed after the original flood risk was assessed but formed part of the design for the works in Roath Brook Gardens as part of the wider scheme.

The initial result estimates the number of properties at flood risk during a 1.33% (1 in 75) chance flood event has reduced to 11. We remain committed to working with partners and the community to find a solution to manage the flood risk, and this risk will only increase due to climate change.

There may be a way to address this remaining risk as part of work that Cardiff Council is considering at Roath Park Lake, upstream of Pen-y-lan. We are discussing this with Cardiff Council and won’t consider further work in Roath Brook and Roath Mill Gardens until these discussions are finalised.

We will inform the local community once this work is complete and what options we have to address the remaining risk.

Before and After Images

 waterloo pergola before waterloo pergola after


A series of photo montages have been prepared to show how the scheme will look before and after the works, once the trees have established, at particular locations along the route and within the Roath gardens.

Tree Removal and Planting

To achieve the required flood protection and construct the new flood walls, embankments and channel widening, unfortunately the removal of some trees along the banks of Roath Brook was required.

For details on tree removal and planting, please email

We understand how the community felt about the trees in the area, so we focused the design efforts to minimise these impacts. For example, by avoiding removing trees around the edge of the park boundaries and replanting higher value trees.

We could not save every tree within the gardens, but tried to get the correct balance of protecting the conservation area and the heritage features of the park, whilst still being able to construct the scheme and meet the required standard of flood protection.

Community Tree Bank

As NRW, our objective is to maintain a positive contribution to the community. We have planted additional trees Roath Park Recreation Ground and have offered tree saplings to school children for home planting.

Contact information

If you have any questions about the scheme, please email

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