]> 2026-04-23T10:01:11+00:00 Case study:Afon Clywdd 500 en Draft Natural Resources Wales AECOM Yes No Yes false No 53.1827018,-3.3687665 Jacques Natural Resources Wales Sisson ,, Runoff pathway management,,,, Runoff pathway management 23743 AECOM, 40 Afon Clywdd.png Planned The Clwyd (Photo 1 and Map 1) is a large catchment in north-east Wales, discharging north into the Irish Sea. The confluence of the Afon Clwyd with the Afon Elwy is downstream of St Asaph, which in November 2012 was subject to severe flooding resulting in a fatality. The impact of flooding from the Afon Elwy, which flows through the town, was exacerbated by the backing up of flow at the confluence with the Afon Clwyd, which was also in spate. In 2015, Natural Resources Wales commissioned AECOM Consultants to identify potential Working with Natural Processes (WWNP) in the Elwy catchment which would provide climate resilience to the proposed improvements to engineered flood defences in St Asaph (AECOM Consultants 2015). Following the study, AECOM wanted to develop techniques for rapid assessment of WWNP that could be applied to different types of catchments. AECOM used EU innovation funding to test techniques in a number of catchments, including this study of potential WWNP in the Vale of Clwyd. A systematic review of the aerial imagery, Ordnance Survey (OS) mapping and flood zone/flood extent information was carried out to identify the most important morphological features in the catchment and to identify locations where the WWNP measures could potentially be implemented across the catchment. In contrast to the Elwy, the identification process included an assessment of implementation and shortlisting to streamline the process. The overall impact of the modelled WWNP is a reduction in peak flow and an increase in time-to-peak (TP). Peak flow reduction was approximately 6% for the 5-year design event and approximately 1% for the 200-year design event. Afon Clywdd afon clywdd http://www.therrc.co.uk/sites/default/files/projects/40_afonclwyd.pdf No Afon Clywdd afon clywdd Flood risk management Habitat and biodiversity Land use management - agriculture Land use management - forestry Water quality 2018-11-08T12:17:45Z 2458431.0123264 2018-11-08T12:30:20Z 2458431.0210648 Afon Clywdd