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Engineering Consultants & Chartered Building Surveyors www. rj. uk. com § § Building Surveying Insurance Surveying Project Management Expert Witness www. richardjackson. uk. c om § § Structural Engineering Civil Engineering Pre-planning & Flood Risk Geotechnical Engineering
Welcome Mark Geddes, Director Richard Jackson Limited www. rj. uk. com
Planning for Flood Risk Management • History • Current Policy – Sequential and Exception tests • How potential solutions translate into planning requirements www. rj. uk. com
History of Flood Management • 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 of Flood Management • Hard engineering systems installed over time Advantages: – Self cleansing – reduces maintenance – Improved public health Disadvantages: – Limited capacity – Out of sight out of mind www. rj. uk. com
History of Flood Management • PPG 25 • Michael Pitt review after flooding in 2007 made a number of recommendations • PPS 25 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
Current Flood Risk Management Policy 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 www. rj. uk. com
The Sequential Test 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 Sequential Test Flooding – understanding your risk www. rj. uk. com
Sources of Flooding www. rj. uk. com
Internal Flooding • Not a planning issue www. rj. uk. com
External Infrastructure • Water Mains • • Adopted Private • Sewers • • • Foul water Surface water Private systems Private, adopted or highways www. rj. uk. com
External Infrastructure • • • 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
Surface Water Flooding - Precipitation • Flood routeing and threshold design • Design for Exceedance www. rj. uk. com
Fluvial Flooding Rivers • Fluvial • • • Rivers Streams Ditches • Causes • • High flow/lack of capacity Blockage www. rj. uk. com
How to assess Fluvial 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
Tidal Flood 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
Ground 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
Reservoirs & 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
Sequential Test • • • 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
Exception Test www. rj. uk. com
Exception Test 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
Exception Test – Part 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
Exception Test – Part 2 Safe for its lifetime – – 60 years commercial 100 years residential Finished floor levels Flood resistance and resilience www. rj. uk. com
Exception Test – Part 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 potential solutions translate into planning requirements 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 potential solutions translate into planning requirements Two main types – How the development form responds to the risks of flood any residual risks – How the development reduces risks on and off site www. rj. uk. com
How potential solutions translate into planning requirements • 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 challenges that remain • 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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