Strategic Flood Risk Assessment - Wiltshire Council

Wiltshire CouncilSFRA High Level Executive SummaryKey Datasets KennetNorthWiltshireSalisbury West WiltshireReservoirs Flood Warning Flood Watch(Hampshire Avon) 3.3 Review of GIS Datasets3.3.1 The Environment Agency updates their flood maps on a quarterly basis, incorporating theresults of detailed studies where relevant. Wiltshire Council have provided updated extents(dated October 2008) of the Environment Agency flood maps to ensure any revisions areincluded in the integrated GIS datasets produced for this high level executive summary.3.3.2 A comparison of existing individual Level 1 SFRAs Flood Zones 2 and 3 with the updatedFlood Zones 2 and 3 provided by the Environment Agency has been undertaken. Althoughthe majority of the flood zones are unchanged, flood zone revisions have been noted andupdated in the following areas:• River Ebble – Flood Zone 3 extent north east of Nunton (Salisbury);• Middle River Kennet – Flood Zone 2 and 3 extent within Marlborough, includingareas upstream and downstream of the settlement (Kennet);• Middle River Kennet – Flood Zone 2 and 3 extent in the vicinity of Mildenhall,Axford, Ramsbury and Chilton Foliat (Kennet);• Upper River Thames – Flood Zone 3 extent in the vicinity of Ashton Keynes(North Wiltshire).3.4 Update and Maintenance3.4.1 SFRAs should be considered as ‘live’ documents where regular review and monitoringshould be undertaken to ensure that the best available data on flood risk issues is beingused to inform Wiltshire Council planning decisions.3.4.2 It is suggested that the GIS layers should form the ‘live’ part of the document. GIS layerupdates should run parallel with the Annual Monitoring Report that typically provideinformation on progress of Local Development Documents, local economy and environment.3.4.3 It is understood that the Environment Agency update their Flood Zone mapping on aquarterly basis and this is distributed to LPAs. It is recommended that a comparison ofexisting and updated Flood Zones is undertaken to identify significant changes in FloodZone 2 and 3. This is particularly important where these have been used as surrogates foreither climate change or Functional Floodplain (Flood Zone 3b) as described within theexisting Level 1 SFRAs.3.4.4 It is recommended that where Functional Floodplain (Flood Zone 3b) is disputed andchanges agreed, these should be recorded to ensure ongoing data maintenance. Where asurrogate has been used to define Functional Floodplain i.e. the whole of Flood Zone 3 hasbeen considered as Functional Floodplain (Flood Zone 3b) in the absence of detailed12 June 2009