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11Employers’ Forum
Introduction to Flooding
byEnvironment Agency, Halcrow andUniversities of Cardiff, Heriot Watt
and Cambridge
33Employers’ Forum
Background• Up to 5m people in U.K. are at risk from river and
coastal flooding
• Annual average damage estimated at £0.7 bn
• Recent floods have been more frequent
• Damage extent exacerbated by:Extensive building on flood plainsAlterations to riverine channelsChanges in recorded rainfall patternsChanges in land management use
• Climate change expected to increase flooding
44Employers’ Forum
Background• River flooding essentially a natural process that
helps shape landscape
• Flooding generally caused by high rainfall and inability of land to drain water effectively - aggravated further when ground saturated
• Flooding frequently leads to serious water pollution and epidemiological problems
• Flood damage extent often exacerbated by: Inadequate flood warning systems Use of crude hydroinformatics tools Inadequately trained model users
3939Employers’ Forum
State-of-art flood guards designed to protect homes and properties from flooding
Accessories designed to complement guards e.g. brick sealant and one-way toilet valves
Based on principle of arch dam design with pressure force used to enhance seal
Simple glass reinforced plastic (GRP) guards:Permanent and unobtrusive narrow frame fixed
around doors and air ventsRemovable curved lightweight guards readily
clipped in place before flooding
Floodguards International
4040Employers’ Forum
• Forces then transmitted to mountain
Arch Dam Principle
Water Pressure
Mountain
Mountain
Arch Dam
• Water pressure transmitted to dam
4141Employers’ Forum
Flood Guard Principle
• Force then used to increase seal efficiency
Water Pressure
House WallHouse Wall Door
Flood Guards
• Water pressure transmitted to flood guard
4444Employers’ Forum
Model of Seepage through Brickwork
Aim:- Predict protection times and seepage for extended flooding
• Research Centre’s model HEMAT used to predict seepage rates through brickwork and under wall foundations
Finite volume method solves flow equations
Irregular triangular mesh used to fit domain
4747Employers’ Forum
Summary of Floodguards
• Based on state-of-the-art technology
• Relatively inexpensive and lightweight
• Frame can be fitted easily and concealed
• Prevents flooding of properties through doors, windows, air vents etc
• Prevents silt and sewage contamination
Benefits
4949Employers’ Forum
Who Are They?• Have over 10,000 staff - mainly scientists,
engineers, planners - responsible for environmental protection
• Have an annual operating budget of over £0.5 billion
• Work in following areas: Air Quality – regulate release of pollutants Conservation – important role, especially along rivers Fish – monitor and study fish habits and ecology Flood – warn public about flood risk and build defences etc Land Quality – seek to prevent land from becoming polluted Navigation – responsible for rivers, estuaries and harbours Recreation – managing use of inland and coastal waters Waste – regulate waste management through licencing Water Quality – ensure quality of surface and ground water Water Resources – monitor and issue abstraction licences
5454Employers’ Forum
Flood Details• Spring 1998:-
Floods lasted 6 days and affected large parts of central and eastern England
More than 1,500 people were evacuated and 5 people died (questionably from floods)
Damage caused was approximately £0.75 billion
• Autumn 2000:- Floods were wettest in U.K. since records began Rainfall in October was four times mean for month More than 10,000 properties were flooded Insurance claims totalled some £0.7 billion damage
5555Employers’ Forum
Lessons from Floods• Flooding impact and damage to property etc was
often much worse where defences were breached• Flooding in parts of catchments often made much
worse by construction on floodplain or elsewhere along river, e.g. flood defences or realignment etc
• Flooding impact exacerbated by responsibility being unclear between local and national authorities
• Government reviews through various bodies have particularly highlighted need for a more strategic and catchment wide approach to flood risk management
• Catchment Flood Management Plans (CFMPs) being prepared for all 80 catchments in England and Wales
5757Employers’ Forum
What Are They?• Three year programme introduced by DEFRA and
Environment Agency to develop Flood Management Plans for all catchments in England and Wales
• Aim is to identify long-term sustainable policies to manage flood risk throughout catchment
• Wide range of issues affect flood risk management: Land use changes Development planning Flood defence works Flood warning and emergency response
• Consideration of flood risks and management solutions at catchment wide scale
5858Employers’ Forum
Summary of Main Steps1. Three year programme introduced by DEFRA and
Environment Agency to develop Flood Management Plans for all catchments in England and Wales
2. Aim is to identify long-term sustainable policies to manage flood risk throughout catchment
3. Wide range of issues affect flood risk management: Land use changes Development planning Flood defence works Flood warning and emergency response Consideration of flood risks and management solutions at
catchment wide scale
5959Employers’ Forum
Summary (Continued)4. Determine existing and future flood risks and
problem areas within catchment
5. Appraise all potential policies and future scenarios for flood risk management - also examine risks upstream and downstream
6. Determine preferred management policies by considering range of alternative scenarios against their relative impact on flood risk
7. Consult on and disseminate preferred CFMP
8. Regularly monitor, review and update CFMP
6060Employers’ Forum
Identify opportunities
and constraints
Periodic review of plan
Define proposals and determine preferred plan (and residual risks)
Define catchment
Determine existing and future flood risks and problem areas
Appraise plan policies for each scenario
Plan dissemination
Understand catchment processes
Identify future change in catchment processes
New or modified plan
Preferred plan consultation Feedback Loop
Scoping study
Collect catchment data and consult with stakeholders
Assess effect on catchment responses and flood risks
Identify future scenariosclimate change / land
use change
Catchment Flood Management Plan Process as Defined in
Guidelines
6161Employers’ Forum
Catchment Data Types• Flood management, e.g. flood defences, flood
warning, existing flood maps, historical data• Catchment processes, e.g. climate, hydrology,
hydraulics, hydro-geology, morphology • Economics, e.g. flood damage estimates, capital
investment, maintenance of defences• Environment, e.g. nature conservation, landscape,
recreation, archaeology, habitat • Land use and planning, e.g. national and
municipal plans, and local plans (e.g. farmland changes)
• Social aspects, e.g. population profiles at risk, sites of high risk facilities such as hospitals
6262Employers’ Forum
Broad Scale Modelling• DEFRA and Environment Agency have introduced
Broad Scale Modelling (BSM) initiative which includes following models: Distributed rainfall-runoff processes River flow routing throughout river basin Effect of all potential flood risk management options on
flood flows Hydro-geological processes where applicable Probability distribution predictions for different drivers
of flooding risk Effects of new developments and land use change Effects of climate change and sea level rise
6363Employers’ Forum
Outputs from CFMPs• Assessment of current position across catchment
• Clear statement of flood risk management objectives
• Preferred long-term and sustainable policies for catchment wide flood management
• Assessment of risks and uncertainties associated with preferred catchment flood management plan
• Timetable for reviews of and revisions to CFMPs
• Up to date list of references and related studies
• Prioritised programme for future monitoring and modelling, and production of strategic plans
7171Employers’ Forum
Water – Some Challenges• 1.2 b people on this earth have no access to safe
drinking water > 3 mpa die of diarrhoea
• 2.4 b people on this earth do not have basic water sanitation > 1 mpa die from hepatitis A
• A child dies in Africa every 30s due to Malaria a disease related to stagnant water
• Flooding often causes many deaths world- wide over 250,000 in Indonesia tsunami
• More than half hospital beds in world filled by people with water related diseases (BMJ 04)
7272Employers’ Forum
“Water is infinitely more critical to lifeon earth than oil”
HRH The Princess RoyalHRH The Princess Royal
Bradford University, Bradford University, 19891989
7474Employers’ Forum
Presentation Produced byProfessor Roger Falconer (Cardiff University)Professor Roger Falconer (Cardiff University)Professor Garry Pender (Heriot Watt Professor Garry Pender (Heriot Watt
University)University)Professor Binliang Lin (Cardiff University)Professor Binliang Lin (Cardiff University)Dr Dongfang Liang (University of Dr Dongfang Liang (University of
Cambridge)Cambridge)Dr Jon Wicks (Halcrow)Dr Jon Wicks (Halcrow)