The current Environment Agency Flood Zones indicate areas that are potentially at risk of flooding from rivers or from the sea.  These show areas that are currently identified to be at risk of flooding under the present day climate.

Flood Zone 3 shows the High Probability zone indicating areas that might be affected by a fluvial (river) flood with a 1% annual exceedance probability (AEP) (or 1 in 100 year return period of occurrence) or greater chance of happening each year.  For tidal areas Flood Zone 3 shows areas that might be affected by a tidal flood with a 0.5% AEP (or 1 in 200 year return period of occurrence) or greater chance of happening each year.

Flood Zone 2 shows the Medium Probability zone indicating areas that might be affected by a fluvial (river) or tidal flood with a 0.1% AEP (or 1 in 1,000 year return period of occurrence) or greater chance of happening each year. 

Areas outside of these Flood Zones are identified as Low Probability risk, and have been identified as having less than 0.1% AEP (1 in 1,000 of flooding from a river or the sea.  Flooding due to other sources, such as surface water or groundwater flooding, may still be likely.

The levels of flood vulnerability in the report are based on data received form the Environment Agency.  They have recently produced a report on Receptors Vulnerable to Flooding (July 2007) which categorises properties based on social or building vulnerabilities.

It should be noted that petrol stations have been assumed as Medium risk as these are not included in the list within the Environment Agency’s report.

Data for social vulnerability to flooding was obtained from the Environment Agency.  The Social Flood Vulnerability Index identifies communities that are likely to be more vulnerable to the adverse health and social effects associated with floods.  This is geographically determined based on four variables that were selected following a review of flood impact studies completed by the Flood Hazard Research Centre.

The four selected variables are: 

1. People aged 75 and over
2. People suffering from a long-term limiting illness
3. Lone parent households
4. Financially deprived households

Northumbrian Water, the sewerage operator in the region, is required by OFWAT to maintain a register of flooding incidents due to hydraulic capacity problems on the sewerage network.  This database identifies locations where flooding occurs on a frequency of 2 incidents in a 10-year period (nominally 1 in 5-year return period) and one incident in a 10-year period (1 in 10 year return period). 

An additional register, for 1 in 20-year return periods, is also maintained.  The 1 in 20 register includes records for flooded properties which are under investigation.  On conclusion of the investigations the properties may be allocated to either the 2 in 10, 1 in 10 or 1 in 20 registers as appropriate, or be recorded separately as properties where flooding has been caused by blockages or other operational problems in the system, or be shown to be the responsibility of a third party.

Northumbrian Water has a prioritisation process for delivering investment projects. The projects generally provide a 1 in 40-year standard of protection to properties identified at risk of internal flooding on the 2 in 10 and 1 in 10 registers.  Currently Northumbrian Water classify storm events greater than a 1 in 40-year return period as extreme and therefore there are likely to be a significantly greater number of properties and areas at risk during a larger magnitude, 50 or 100 year (2% or 1% annual probability) storm.

A study was recently completed by the Environment Agency to determine the likely effects of climate change on the estimated indicative areas already identified to be at risk of flooding.  This study considered a 20% increase in river flows for a future horizon in approximately the 2080s, based on recommendations from the Government’s Foresight flooding report.  This is generally in line with the predicted increases in rainfall estimated across the region, although somewhat exaggerated for some areas, particularly those along the coast. 

The increase in river flow has been applied over the previous flood zone risk areas on a national scale to determine a high-level sensitivity analysis of the possible effects of climate change within any given catchment.  This has produced a new layer of flood zones which crudely determine the depth difference of future river flood levels.

For the North East regional study, we have categorised this depth difference data to determine areas where significant increases in flood level are expected.  The data has been classified into ranges of future flood risk impact depending on the future depth increases determined.

For the high risk areas we have reviewed the surrounding property dataset information to estimate the additional properties, assets and public buildings that might be affected by future flooding problems. 

Flooding to the region’s transport networks has been undertaken at a regional broadscale.  The estimated impacts on roads and rail systems have been determined based on the locations where the Environment Agency’s Flood Zones affect road or rail crossings.  This has been based on the high probability Flood Zone 2.

This assessment does not take into account where crossings are at a higher level above the river or estuary, and obviously raised bridges will prevent the networks from being affected.  However, the sections identified highlight the potential risk of flooding posed to the relevant transport systems.  Lower sections either side of the crossing are likely to be affected.  The Flood Zones are based on available local topography data, so where these affect areas either side of a crossing it is highly likely that sections of the road or rail networks may flood.

In addition, to the direct impacts, flooding around bridge abutments is likely to cause increased scour and erosion problems.

It should be noted that the Environment Agency’s flood vulnerability report identifies motorways, primary and main roads as high vulnerability, and it is recommended that the individual identification should be based on usage and traffic ‘population’.

The Regional Flood Defence Committee is an executive Committee of the Environment Agency.  It is tasked with directing the flood risk management work of the Agency and with raising a Local Levy from Local Authorities.  This Levy is used to deliver a programme of work centred on flood risk issues, but with climate change as a core priority.  The Local Levy has part funded this particular study.