Engineering Consultants & Chartered Building Surveyors www.rj.uk.com Building Surveying Structural Engineering Insurance Surveying Civil Engineering Project Management Pre-planning & Flood Risk Expert Witness Geotechnical Engineering www.richardjackson.uk.co m
We Welco come me Mart rtin n Do Doughty ghty, , Di Dire rector tor Richard Jackson Limited www.rj.uk.com
Pl Planning anning for Flood od Risk k Management anagement • History • Current Policy – Sequential and Exception tests • How potential solutions translate into planning requirements www.rj.uk.com
History tory of Flood od Management anagement • Parish based maintenance of drainage infrastructure • Break up of water industry post 1974 worsened the situation interested parties include – Environment Agency – Highways Authorities – Sewer Authorities – Lead Local Flood Authorities – Internal Drainage Boards – Local Authorities – Land Owners • Little joined up thinking and silo approach www.rj.uk.com
History tory of Flood od Management anagement • Hard engineering systems installed over time Advantage tages: s: – Self cleansing – reduces maintenance – Improved public health Disadvanta dvantages: – Limited capacity – Out of sight out of mind www.rj.uk.com
History tory of Flood od Management anagement • PPG 25 • Michael Pitt review after flooding in 2007 made a number of recommendations • PPS25 and then NPPF • Flood and Water Act: Reduce flood risk Improve flood risk management Risk based approach on Reservoirs Encourage use of Sustainable Urban Drainage Systems Enhance water quality Improve water management in drought Financial changes www.rj.uk.com
Cur urrent ent Flood od Risk k Management anagement Po Policy cy National Planning Policy Framework And Planning Practice Guidance These require a two stage approach – The sequential test – The exception test Local Policy • Shoreline Management Plans • Catchment Flood Management Plan • Local Plan • LLFA Standing Advice • Strategic Flood Risk Assessments • Surface water management plans www.rj.uk.com
The he Seq eque uential ntial Tes est NPPF Section 10 Meeting the challenge of climate change flooding and coastal change Para 101 “ The aim of the sequential test is to steer new development to areas with the lowest probability of flooding. Developments should not be allocated or permitted if there are reasonably available sites appropriate for the proposed development in areas with a lower probability of flooding. The Strategic Flood Risk Assessment will provide the basis for applying this test. A sequential approach should be used in areas known to be at risk from any form of flooding.” www.rj.uk.com
The he Seq eque uential ntial Tes est Flooding – understanding your risk www.rj.uk.com
Sour urces ces of Fl Floodin ding www.rj.uk.com
In Intern rnal l Floo oodi ding ng Not a planning issue • www.rj.uk.com
Extern rnal al In Infra rastructure structure Water Mains • Adopted • Private • Sewers • • Foul water • Surface water Private systems • Private, adopted or highways www.rj.uk.com
Exte ternal rnal In Infrastructure rastructure • How to assess risk currently difficult • Lead Local flood Authority – County Councils • Sewers are generally designed for 1 in 1 or, 1 in 30 year events • Water Companies maintain a list of assets that have flooded • Planning policy requires new developments to respond to 1 in 100 year event with climate change www.rj.uk.com
Sur urface face Wa Wate ter Flooding oding - Pr Prec ecipitati pitation on • Flood routeing and threshold design • Design for Exceedance www.rj.uk.com
Fluvi vial al Floo ooding ing - Rivers rs Fluvial • Rivers • Streams • Ditches • Causes • • High flow/lack of capacity Blockage • www.rj.uk.com
How to assess ss Fluvi vial al Risk What zone are you shown to • be in on Environment Agency mapping Review strategic flood risk • assessment Is there a source near your • site What is the landform like • Is there a culvert that may • cause a blockage If a main river ask • Environment Agency If a water course ask Local • Authority www.rj.uk.com
Ti Tidal Floo ood d Risk What zone are you shown to • be in on Environment Agency mapping What does the strategic • flood risk assessment say How far is the sea/estuary • Is there any defence or • barrier – is it high enough If so ask how this is • managed and maintained What is the policy in the • Shoreline Management Plan for the area www.rj.uk.com
Gro roun und d Water Not currently mapped by • anybody although suitable geology is Environment Agency and • Local Authority may be aware if there is a history The Environment Agency • are gathering information about this risk Is your building in an • area that could retain water e.g. low depression www.rj.uk.com
Reservo rvoirs rs & Ca Canals Often hold water above • ground level Environment Agency • mapping available Risk of flooding associated • with failure Monitored under Reservoirs • Act currently www.rj.uk.com
Seq eque uential ntial Tes est • There is no fixed way to apply the sequential test • It could be district/borough wide • Smaller regeneration areas can be ring fenced • Marketing areas can be defined • Exception sites for affordable housing www.rj.uk.com
Excepti ception on Tes est www.rj.uk.com
Excepti ception on Tes est NPPF para 102 • It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a strategic flood risk assessment where one has been prepared; and • A site specific risk assessment must demonstrate that the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and where possible will reduce flood risk overall. www.rj.uk.com
Excepti ception on Tes est t – Pa Part t 1 • Responds to the Local Development Plan • Provides housing where there is a 5 year land supply deficit • Provides needed facilities www.rj.uk.com
Excepti ception on Tes est t – Pa Part t 2 Safe for its lifetime – 100 years unless limited life proposed – Finished floor levels – Flood resistance and resilience www.rj.uk.com
Excepti ception on Tes est t – Pa Part t 2 Taking account vulnerability of its users – Safe access and egress – Evacuation in events (Emergency Planners) Without increasing flood risk elsewhere – Consume your own smoke – Match existing surface water run off rate (SUDS) Where possible reduce flood risk overall – Brownfield sites reduce run off by using SUDS www.rj.uk.com
How poten ential tial so solutions tions translate slate into plann nning ing req equire ireme ments nts Building Safe – Raise floor levels – Structural integrity – Flood resistance, barriers, valves land raising – Flood resilience, suitable construction and less vulnerable use on lower floors People Safe – Access and egress during design flood events – Warnings and evacuation if appropriate – Refuge for defence failures and extreme events www.rj.uk.com
How poten ential tial so solutions tions translate slate into plann nning ing req equire ireme ments nts Two main types – How the development form responds to the risks of flood and any residual risks – How the development reduces risks on and off site www.rj.uk.com
How poten ential tial so solutions tions translate slate into plann nning ing req equire ireme ments nts • Reduction of surface water run off rate – SUDS • Opportunities to reduce existing flooding by returning brown field sites to pre-development condition www.rj.uk.com
The he cha hallenges llenges th that at rem emain ain • Adoption – Planning policy and adoption are out of step - Still – Maintenance who pays for SUDS maintenance • Strategic defence improvements on the shoreline • Upstream impounding schemes to protect existing urban areas of risk • Retrofit water reuse systems • Garden paving enforcement • Retrofit SUDS to existing built environment www.rj.uk.com
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