Flood Risk Assessment

JBA Flood Alleviation Digger

We are supporting Risk Management Authorities, Local Planning Authorities and Developers, to identify suitable development areas and design flood mitigation schemes for areas, where there may be some risk of flooding, by undertaking:

  • Strategic flood risk and consequence assessments (SFRAs, SFCAs) that will form an integral part of the local authorities’ evidence base, in terms of identifying appropriate locations for development and underpinning local flood risk management policies and strategies.
  • Site-specific flood risk assessments (FRAs) that will provide a more refined assessment of the flood risk to and from a development site, over its lifetime, in order to satisfy the requirements of the local planning authority.
  • Modelling and mapping studies that provide improved information on the likelihood, nature and consequences of flooding that can be used by those responsible for managing flood risk to inform spatial, emergency and investment planning decisions.

This will provide a general indication of the potential flood risk to the site and identify whether there are any flooding or surface water management issues that may warrant further investigation. The purpose of a Level 1 Screening Study is to identify all sources of flood risk and whether any further work in the form of a Level 2 FRA (Scoping Study) or Level 3 FRA (Detailed Study) is required.

Typically included items:

  • Assessment of readily available existing flood risk information (supplied by Argyll Environmental Ltd)
  • Initial comments on the feasibility of developing the site with reference to existing flood risk information
  • Comments upon the feasibility of developing the site with respect to NPPF, including advice on the requirements of the Sequential and Exceptions Tests
  • Review of existing drainage information
  • Recommendations for further work/investigations.

Qualitative appraisal to develop understanding of the risk of flooding to the site and the potential impacts the development will have on flood risk elsewhere. Production of a FRA report in accordance with NPPF.

Typically included items in addition to Level 1 items:

  • Contacting the Environment Agency, Local Planning Authority and Sewerage Undertaker to obtain advice on flood risk and drainage issues at the site (including obtaining predicted flood levels and copy of the statutory sewer map if available)
  • Comparison of site levels with predicted flood levels
  • Assessment of the impact of water level increase due to climate change
  • Recommend finished floor levels
  • Assess access and escape routes in times of flood
  • Give preliminary advice on flood warning and evacuation procedures
  • If required, recommend appropriate mitigation measures e.g. flood resilient construction techniques
  • Preliminary assessment of the existing and proposed surface water drainage arrangements.

Undertaken if the Environment Agency require further quantitative analysis to assess flood risk issues relating to the development site. For example; Flood Modelling may be required to establish flood levels at a site where the Environment Agency do not hold this data.

Typically included items in addition to Levels 1 and 2:

  • Detailed assessment of flood risk to the site from all sources (including the assessment of the potential impacts of climate change)
  • Hydraulic calculations and modelling to quantify the flood risk to the site and any offsite flood risk impacts
  • Detailed assessment of existing and proposed surface water drainage arrangements (including the feasibility of Sustainable Drainage Systems (SuDS) and surface water attenuation facilities if required)

Sustainable urban Drainage Systems (SuDS)

New developments have the potential to cause an increase in impermeable areas, an increase in surface water runoff rates and volumes, and a consequent increase in downstream flood risk due to overloading of sewers, watercourses, culverts and other drainage infrastructure. Managing surface water discharges from new developments is therefore crucial.

The Planning System has a key role to play in setting standards for sustainable drainage from new developments and ensuring that they are designed to take into account the risk from surface water flooding. Sustainable drainage plays an important part in reducing flows in the sewer network and in meeting environmental targets, alongside investment in maintenance and new capacity by water utilities companies.

We can help you

If you would like to discuss how we can work together please contact Peter May.

Email Peter May, Head of Flood Resilience
+44 (0)1633 413 514