Entec and FRM > Project experience: Wales
St Athan Flood Consequence Assessment
Client: Land Securities Trillium
This is part of a much wider multi-disciplinary project providing planning and environmental impact advice on the proposed Defence Training Academy for South Wales. It is one of the largest public-private partnership contracts to be undertaken in the UK, valued at £10 billion, and Entec has been involved since 2005 on behalf of the developer, Metrix, and its owners Land Securities Trillium and Qinetiq. The purpose of the flood consequence assessment is to accurately assess flood risk across the project area based upon the Drainage Strategy proposals. An associated EIA hydrological assessment is to assess the effects of the development on all water receptors in terms of water quantity, quality and morphology.
The FCA requirements are prescribed in Technical Advice Note 15: Development and Flood Risk (TAN15). TAN15 provides technical guidance to supplement the policy set out in Planning Policy Wales (PPW) 2002 in relation to development and flooding. TAN15 advises on development and flood risk and provides a framework within which risk arising from river and coastal flooding, and/or from additional run-off from development in any location can be considered when assessing planning applications.
In assessing flood risk, the following specific considerations are expected to be made:
- The likely mechanisms of flooding
- The likely sources of flooding (including fluvial, coastal, minor watercourses, groundwater, surface runoff, sewerage blockages or any other sources of flooding)
- The depths of flooding throughout the site
- The speed of inundation of the site
- The rate of rise of floodwaters throughout the site.
- Velocities of floodwaters across the site
- Overland flood routes
- The effects on access and egress and infrastructure, for example public sewer outfalls, combined sewer overflows, surface water sewers and effluent discharge pipes from waste water treatment works
- The impact of the development in terms of flood risk on neighbouring properties and sites.
Caerphilly Flood Consequence Assessments
Client: Caerphilly County Borough Council
Entec has been commissioned to prepare strategic flood consequence assessments at two sites in Caerphilly, south Wales. One site is a former colliery identified for residential development in the emerging Local Development Plan. The other is an existing industrial estate with the strategic flood consequence assessment seeking to inform options for the potential redevelopment for employment-based uses.
The River Ebbw flows through the colliery site and the River Rhymney through the industrial site. The SFCA will involve hydraulic modelling of both sites to assess the risk from the 100 year flood and including the impacts of climate change. Both watercourses are currently culverted through parts of the site and the study will look at the option of opening up the culverts. At the colliery site the issue of flooding from existing mineshafts will also be addressed.
The study will assess whether the sites can be developed in line with TAN15 (Welsh Assembly Government guidance: Development and Flood Risk) requirements, and what mitigation options may need to be considered at the detailed flood risk assessment stage.
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