Annex G

Flood Warning Service Information

Annex G1 Environment Agency Flood Warning Codes (extracted from the EA website) http://www.environment-agency.gov.uk/homeandleisure/floods/31620.aspx

The Environment Agency warning service has three types of warnings that will help prepare for flooding and take action.

They are:

• Flood Alert • Flood Warning • Severe Flood Warning

[Note: Flood warning and Severe Flood Warning are not specifically applied to groundwater flooding, but these definitions have been included here for completeness as they remain pertinent to areas that suffer both groundwater and fluvial flooding ]

Flood Alert

What it means: Flooding is possible. Be prepared.

When it's used: Two hours to two days in advance of flooding. What to do: Be prepared to act on your flood plan. Prepare a flood kit of essential items. Monitor local water levels and the flood forecast on our website.

Flood Warning

What it means: Flooding is expected. Immediate action required.

When it's used: Half an hour to one day in advance of flooding. What to do: Move family, pets and valuables to a safe place.

Turn off gas, electricity and water supplies if safe to do so. Put flood protection equipment in place.

Severe Flood Warning

What it means: Severe flooding. Danger to life.

When it's used: When flooding poses a significant threat to life.

What to do: Stay in a safe place with a means of escape.

Be ready should you need to evacuate from your home. Co-operate with the emergency services. Call 999 if you are in immediate danger.

Warnings no longer in force

What it means: No further flooding is currently expected in your area.

When it's used: When river or sea conditions begin to return to normal. What to do: Be careful. Flood water may still be around for several days. If you've been flooded, ring your insurance company as soon as possible.

Annex G2 Environment Agency Information: regional groundwater levels and conditions

G2.1 Water Situation Reports Water situation reports are issued monthly throughout the year both on a national ( and Wales) basis and for all Environment Agency regions (and some Environment Agency Areas). Within , water situation reports are provided as follows: • South East Region; o (South East Region); Solent and South Downs Area; o (South East Region); West Thames Area; • South West Region; o (South West Region); Wessex Area. These reports can be found at: http://www.environment- agency.gov.uk/research/library/publications/33995.aspx Extracts from (part of) a water situation report are reproduced below. These reports provide a monthly summary of hydrological conditions and water resources in each Region and Area, including information on rainfall, soil moisture deficit, river flow, groundwater levels and reservoir storage. The reports include maps, graphs and plots and the text and diagrams showing the general groundwater situation and emerging trends and are intended to be relatively easy to understand, even for the lay reader. Groundwater level charts show (for selected and representative monitoring wells across the region) current water level data as well as a range of historically recorded values in bands comprising 7 categories between exceptionally low to exceptionally high (see below for an explanation of these terms). Each monitoring well used to develop the report is shown on a regional map and the (current) water level category colour coded. A typical set of these graphs is also shown below. Some water situation reports (e.g. West Thames Area) also show the dry and flowing lengths of ephemeral (groundwater fed) rivers.

Annex G2 Environment Agency Water Situation Report – example extract

Summary Page

Annex G2 Environment Agency Water Situation Report – example extract Groundwater Information

Annex G2 Environment Agency Water Situation Report – example extract Groundwater Information

Annex G2 Environment Agency Water Situation Report Categories and Definitions

Category Definition

Exceptionally high Value likely to fall within this band 5% of the time

Notably high Value likely to fall within this band 8% of the time

Above normal Value likely to fall within this band 15% of the time

Normal Value likely to fall within this band 44% of the time

Below normal Value likely to fall within this band 15% of the time

Notably low Value likely to fall within this band 8% of the time

Exceptionally low Value likely to fall within this band 5% of the time

G2.2 Groundwater Briefing Notes In addition to the Water Situation Reports, The Environment Agency also publishes flooding from groundwater “Briefing Notes” which may be issued in certain areas when groundwater levels are high (in excess of seasonal averages). These briefing notes, which are only issued when groundwater levels are rising and have reached a pre determined threshold level (see further below) provide a summary of the current situation, identify where flood alerts are active, provide a qualitative forecast of the risk of flooding and indicate actions being taken and appropriate contacts. The Environment Agency also publish groundwater level information for key boreholes used in the monitoring groundwater flooding (see Figure above). The flooding from groundwater briefing notes and water level monitoring information can be found at:

http://www.environment-agency.gov.uk/homeandleisure/floods/137320.aspx

and

http://www.environment- agency.gov.uk/research/library/publications/99556.aspx An example extract of a “Flooding from groundwater” briefing note for Solent and South Downs area is reproduced herein (included as a separate document, Annex G5) Solent and South Downs Area of the Environment Agency have a developed set of procedures ( Ref 10 ) for groundwater flooding which sets out the actions they will take based on monitoring a set of boreholes across their area (see further below). These procedures are based on national guidance issued internally by the Environment Agency for operating a groundwater flood warning system.

Annex G3 Environment Agency Groundwater Flood Warning Service

G3.1 Groundwater Flood Alerts

The Environment Agency provides groundwater flood alerts through its website and through Flood Warnings Direct (for those who sign up for the service). Currently the Environment Agency issue groundwater flood alerts to 19 areas within Hampshire.

These flood alert areas (shown in Annex B Figure 5) have been selected primarily based on the groundwater flooding experienced during 2000/2001 and give good coverage of the areas most at risk from groundwater flooding.

Alerts are issued when groundwater levels in a series of monitoring boreholes (or “warning wells”) reach certain pre determined (and regularly reviewed) trigger levels.

G3.2 Groundwater Flood Monitoring - Warning Wells

Groundwater flooding “warning wells” are monitoring boreholes operated by the Environment Agency to observe the rise and fall of groundwater which include a specific function to monitor the extreme rise of groundwater that may lead to groundwater flooding. A number of these wells are equipped with telemetry (telemetric monitoring boreholes) which allows the water level data to be sent by telecommunication and observed remotely at the Environment Agency Area office.

In the procedures followed by the Environment Agency in the monitoring of groundwater flooding warning wells vary between their different regions and areas.

In the procedures set out followed by the Environment Agency Solent and South Downs Area, 15 boreholes (11 relevant to Hampshire), equipped with telemetry (i.e. which may be read remotely at the EA office) are identified. There are also supporting “key” boreholes which are used to gather more local supporting information. These are routinely measured monthly and then more frequently in response to triggers set in the telemetry boreholes.

Each telemetred borehole and supporting key borehole are used to monitor flood risk in a particular area (known to be at risk from groundwater flooding from historic records). Up to 4 trigger levels may be identified in each borehole with a corresponding set of actions and or consequences (e.g. trigger levels may represent the onset of cellar flooding in some areas).

A summary of these warning wells and those in the Wessex and West Thames EA Areas together with the area they cover is given in Table G3.1 below.

Procedures in the Wessex Area and West Thames Areas appear less defined, although they also operate similar telemetric monitoring wells.

A summary of all the warning wells operated in Hampshire, together with the area they cover is given in Table G3.1 below.

Example flood alert messages are shown below.

The public may sign up for email communication of groundwater flood alerts through Flood Warnings Direct, and there are direct access phone lines available (see also Table G3.1).

Table G3.1 Environment Agency Groundwater Flood Alert Areas and Associated “Warning Wells”

GW Current flood Quickdial EA Key Groundwater River Flood alert Environment Agency Groundwater Flood Alert Area Corresponding telemetry well Villages Covered Code Area boreholes Body Catchment Alert area 06/02/12 label Upper Hampshire Pitton, West 1 Salisbury Plain Area 0452 Wessex Lopcombe Corner Hampshire Avon Pitton, Broughton, , y Tytherley Avon (R.Bourne) West Ashe (Ashe Basingstoke 2 Basingstoke and Sherborne St John 171907 Oakley Loddon Deane, Ashe y Thames Warren) Chalk

West Basingstoke 3 Crondall 171908 unknown unknown Loddon Crondall n Thames Chalk

West Alton Upper 4 Alton 171909 unknown unknown Wey Alton, Chawton and Lower Farringdon areas y Thames Greensand

Solent and Pitton, West River Test Test and 5 Pitton, West Tytherley, Nether Wallop and Broughton 0122623 Lopcombe Corner Pitton, Broughton, Nether Wallop, West Tytherley y South Tytherley Chalk Itchen Downs Solent Kings and Somborne River Test Test and 6 Kings Somborne and 0122624 Kings Somborne, Compton Ems Kings Somborne, Little Somborne y South (Folly Chalk Itchen Downs Farm) Solent and River Itchen Test and 7 Hursley 0122631 Hursley Hursley n South Chalk Itchen Downs Solent and Bishops River Itchen Test and 8 Headbourne Worthy and Littleton 0122632 Harestock Littleton, Headbourne Worthy, y South Sutton Chalk Itchen Downs Solent and Bishops River Itchen Test and 9 Bishops Sutton 0122633 Preston Candover & Harestock Bishops Sutton y South Sutton Chalk Itchen Downs Solent Old and River Itchen Test and Preston Candover, Brown Candover, Chilton 10 Candovers and Old Alresford 0122612 Preston Candover Arlesford, n South Chalk Itchen Candover, Bishops Sutton, Old Arlesford Ashe Downs Cheriton Solent and and River Itchen Test and 11 and Cheriton 01222634 Hut? Bramdean Bramdean, Cheriton, , Twyford n South Chalk Itchen (Cheriton Downs Wood) Solent Meonstoke, East and , East Hants Soberton, Droxford, Meonstoke, , 12 Meon Valley from Soberton to East Meon 0122641 West Meon Hut Hampshire n South Cheriton Chalk Exton, , West Meon and East Meon (R.Meon) Downs and

Bramdean (Cheriton Wood)

Hambledon Solent (Whitdale), East and East Hants 13 Hambledon 0122636 Broadpennyhalf Down Meonstoke Hampshire Hambledon, Denmead, Meonstoke, Soberton n South Chalk (Pound (R.Wallington) Downs Lane) Solent Denmead, East East Hants and Meonstoke Hampshire 14 Denmead 0122637 Broadpennyhalf Down Lambeth Hambledon, Denmead, Meonstoke, Soberton n South (Pound (R.Potwell Group Downs Lane) Trib) Solent East and East Hants 15 Finchdean, Dean Lane End and Rowlands Castle 0122642 Chalton Finchdean Hampshire Finchdean, Dean Lane End, Rowlands Castle y South Chalk (R.Lavant) Downs Solent Test and and Ashe (Ashe River Test 16 Deane and Ashe in North Hampshire 0122611 Oakely Itchen (Test Deane, Ashe y South Warren) Chalk (Upper)) Downs Solent Test and and River Test Vernahm Dean, Upton, , St 17 Vernham Deane, Upton and the Bourne Valley 0122621 Vernham Deane Itchen (Bourne y South Chalk Mary Bourne Rivulet) Downs Solent Test and Hatherden, and River Test Itchen (Pillhill Hatherden, Penton Mewsey, Kimpton, 18 Villages to the north east of Andover 0122622 Gate , y South Chalk Brook and Appleshaw, Bottom, , Kimpton Downs R.Anton) Bishopstone, Bourton, Braemore, Britford, Sutton Hampshire Broadchalk, Burgate, Chilmark, Downton, Scotney Upper Avon Farnham, Fordingbridge, Hinton St. Mary, Mere, 19 Groundwater flooding in Cranborne Chase 04515 Wessex West Woodyates (Upper Hampshire n (Hampshire Pimperne, Ringwood, Rockbourne, Shapwick, Cranborne Avon Avon Lower) Sixpenny Handley, Tarrant Gunville, Tarrant Farm) Hinton and Tarrant Monkton

Annex G3 Environment Agency Groundwater Flood Alert – Example Messages

Annex G4 Flood Guidance Statement - example