The role of building flood resilience within flood

The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer © HR Wallingford 2005

Outline Overview and definition of resistance / resilience Research basis for new guidance Guidance overview Example of resilient home Future developments Page 2 * 3/5/2021

Evolution of approach to floods “Act of God” • Accept the vagaries of nature Man against nature • Flood defence, control or management Recognise social and environmental dimensions • “Living with rivers” Flood risk management • • Page 3 * 3/5/2021 A portfolio of policies and actions “Room for the river” (NL, 2000) “Making Space for Water” (UK, 2004) New EU Directive (2007)

Flood Risk Management Practice Post-flood measures Relief, clean-up, reconstruction, regeneration, etc. Pre-flood measures Preventive risk management Spatial planning, contingency plans, flood defence (mitigation) measures, insurance, preparedness, etc. Flood event measures Real time risk management Forecasting and warning, reservoir control, evacuation, rescue, etc. Page 4 * 3/5/2021

Hierarchy of flood mitigation approaches Definitions • Flood avoidance constructing the building in such a way that it avoids being flooded, e. g. by raising it above flood level • Flood resistant constructing the building to prevent flood water entering the building or damaging its fabric. This has the same meaning as flood proof • Flood resilient constructing the building in such a way that minimises water ingress and promotes fast drying and easy cleaning, and does not cause any permanent damage • Flood repairable constructing the building in such a way that although flood water enters the building, elements that are damaged by flood water can be easily repaired or replaced Page 5 * 3/5/2021

Research/responses for flood mitigation • Flood avoidance PPS 25 and use of Flood Risk Assessments to determine flood risk and inform design • Flood resistant testing of flood protection products via kitemark scheme (to address doorways and other openings) • Flood resilient recent project to address other ‘weak points’ in walls, floors, joints • Flood repairable wide experience from flood repair industry (‘PAS 64’, ‘Standards for repair’, ‘Repairing flooded buildings’) Page 6 * 3/5/2021

Recent project (1) ‘Improving the flood resilience of buildings through improved materials, methods and details’ Funders • DCLG & Defra / Environment Agency with: – – – Page 7 * 3/5/2021 NHBC Scottish Building Standards Agency Council of Mortgage Lenders Concrete Block Association CIRIA Core members

Recent project (2) Consortium • • • CIRIA HR Wallingford Leeds Metropolitan University WRc Waterman Burrow Crocker Timeframe January 2005 to February 2007 Contributes to ‘Making Space for Water’ (Defra) Page 8 * 3/5/2021

Resilience – main issues Flood resilience • Limiting the damage • Reducing time to re-occupy • Health & safety issues – stress and the disruption to normal lifestyle • Cost of repairs (Promoted by insurers) Outcomes • A guidance document for key stakeholders • Methodology to incorporate methods and techniques into the Building Regulations Page 9 * 3/5/2021

WP 2 – Review of existing knowledge Page 10 * 3/5/2021 • Reviewed experience and evidence from around the world • Very difficult to provide total flood resistance • Much of existing knowledge based on expert advice, assumptions and extrapolations • The advice is in the main derived from experience and a common sense approach • General lack of scientific experimental data • Little published scientific research into the performance of buildings and construction materials in floods, with only limited attempts to collect and analyse experiential data

WP 6 (Collation & analysis of postflood data) • Many interviews with key groups/individuals involved in flood repair industry • Liaison with other initiatives (e. g. flood resilient house built as part of FLOWS project) • Review of new documents (PAS 69, ‘Repair of flooded buildings’) • Analysis of drying data • Largely confirms findings of WP 2 review • Lack of hard evidence • Lack of agreement on definition of resilience Page 11 * 3/5/2021

WP 5 – Laboratory tests Testing programme: • Stage 1 – Building materials • Stage 2 – Walls • Stage 3 – Floors • Stage 4 – Promising / Innovative materials Page 12 * 3/5/2021

WP 5 – Laboratory tests of building materials Test procedure (mimicking flood conditions) Two phases: - Wetting phase: up to 4 days (48 hours) ; testing units are exposed to still flood water 1 m deep - Drying phase: 7 days (168 hours); test units allowed to dry naturally under laboratory ambient conditions Page 13 * 3/5/2021

Elements tested Page 14 * 3/5/2021

Test results Hand-made brick Seepage through Handmade brick Page 15 * 3/5/2021

Stage 2 - Testing of walls Test rig – two identical test rigs Page 16 * 3/5/2021

Test results – illustrative examples Plaster board Page 17 * 3/5/2021 Wall ME 1 (Eng Bricks on external face and Concrete blocks on internal face) during wet test

Flood resilience characteristics Water penetration – the seepage through the material (different from “water absorption”) Drying ability – the capability to regain the original moisture condition Retention of pre-flood dimensions, integrity – the lack of deformation or change in form or appearance of the material Page 18 * 3/5/2021

Summary information for Guidance * Resilience characteristics are related to the testing carried out and exclude aspects such as ability to withstand freeze/thaw cycles, cleanability and mould growth Page 19 * 3/5/2021

New Guidance May 2007 Launched by Minister Page 20 * 3/5/2021

Page 21 * 3/5/2021

Proposed changes to Building Regulations New requirement in Part C* - Resistance to the effects of flooding: • An FRA/FCA – mirroring requirements in PPS 25/TAN 15 • Requirement to incorporate reasonable measures to mitigate the effects of flooding • Adequate means of refuge/escape • Safe during floods without increasing risk to emergency services • * Site preparation and resistance to contaminants Page 22 * 3/5/2021

Closing the loop between Planning and B. Regs. Proposals to B Regs – expected to be implemented in 2008/09 – aim to close the loop between: Planning system - key responsibility to determine whether flood effect mitigation is required Building control - responsible for its application In practice, proof of compliance to amended Part C to be sent to LPA prior to commencement of building work Page 23 * 3/5/2021

Resilient House (1) Page 24 * 3/5/2021

Resilient House (2) Page 25 * 3/5/2021

Concluding remarks • Await amendment to Building Regs. – will it happen? • Recent project on ‘encouraging uptake of resilience’ • Pilot studies on resilience measures – update end May • Has new Guidance being used? • Clear benefits from resilience, BUT - Needs incorporating into policy Page 26 * 3/5/2021 - Uptake for existing properties would provide greater benefits