Norwich Urban Area SWMP

Norfolk County Council has been working with Norwich City Council, Broadland Council, South Norfolk Council, the Environment Agency, Anglian Water and consultants URS/Capita Symonds to produce a Surface Water Management Plan (SWMP) for the Norwich Urban Area.

Detailed modelling of extreme rainfall events and surveying has been undertaken to identify areas that are more susceptible to surface water flooding.

All relevant stakeholders who could be affected by or have an input towards mitigating surface water flooding were contacted during the project; workshops were held in each of the Critical Drainage Catchments (CDC’s). These helped to shape the outputs of the project. 


Norwich was identified as one of the top 50 candidate areas outside London to receive Defra SWMP funding, based upon broad-scale national predictive surface water modelling that suggested that approximately 6,500 properties may be at risk from surface water flooding.

The Norwich SWMP commenced in September 2010 and was adopted by the Council in May 2012.  Modelling was undertaken for the entire urban area of Norwich and detailed modelling was carried out for the areas most at risk. These areas were identified as Critical Drainage Catchments (CDC).

All relevant stakeholders who could be affected by or have an input towards mitigating surface water flooding were contacted during the project and workshops were held in each of the CDAs.  These helped to shape the outputs of the project.

One of the key outputs from the Norwich Urban Area SWMP was detailed surface water flood risk maps.  These maps are being used to prioritise maintenance of drainage systems, planning policies and help shape funding bids for mitigation works.

Further work on the Norwich SWMP (completed in November 2014) provided more accurate data on the catchments of the Critical Drainage Catchments and cost benefit analyses of the flood protection measures.  This information has helped our understanding of the range and scale of effective mitigation measures which has fed into bids for future funding.

Use of surface water flood mapping within the report and appendices

Note that the Norwich Surface Water Action Plan maps only show the predicted likelihood of surface water flooding (this includes flooding from sewers, drains, small watercourses and ditches that occurs in extreme rainfall events) for defined areas, and due to the coarse nature of the source data used, are not detailed enough to account for precise addresses.

Individual properties therefore may not always face the same chance of flooding as the areas that surround them.  There may also be particular occasions when flooding occurs and the observed pattern of flooding does not in reality match the predicted patterns shown on these maps.

To the extent permitted by law Norfolk County Council ("We" or "we") will not be liable if the maps by their nature are not as accurate or complete as might be desired and we make no representation or warranty, express or implied, that the maps will be accurate, complete or up to date.

We have taken reasonable measures to ensure that the maps reflect all the data we possess and in good faith have applied our knowledge to create reasonable conclusions.

It is essential that anyone using these maps fully understands the complexity of the data utilised in production of the maps, is aware of the limitations and does not use the maps in isolation. Users of these maps should refer to Section 2.3 of the Norwich Urban Area Surface Water Management Plan report for a complete description of the limitations and accuracy of the flood or hazard extents shown.

These maps provide a strategic overview of surface water flood risk and may be subject to further analysis in the future.  By downloading the documents below you accept the use of the surface water mapping in their production.

All intellectual property rights in the data and information on this web site are owned by the Norfolk County Council or are licensed from other third party data providers.

Flood investigation reports

Norwich and Broadland

Norwich Urban Area SWMP: Stage 2 report, appendices and maps

Norwich Urban Area SWMP further studies: report and appendices

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