Issues of Urban Flooding - University of Sheffield/file/Sheperd-2007.pdf · Issues of Urban...

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Issues ofIssues ofUrban FloodingUrban Flooding

Dr Will ShepherdDr Will ShepherdPennine Water Group,Pennine Water Group,University of SheffieldUniversity of Sheffield

Pennine Water GroupPennine Water GroupEPSRC Platform Grant, based at universities of Sheffield and BradfordResearch areas: potable water, stormwater and wastewater service provision and management of associated assetsMulti-disciplinary including civil engineering, economics, bio-chemistry, sociology and psychology

DefinitionDefinitionFlood: ‘An overflowing or irruption of a great body of water over land not usually submerged’ (Oxford English Dictionary)

DefinitionDefinitionUrban: ‘Pertaining to or characteristic of, occurring or taking place in, a city or town’ (Oxford English Dictionary)

Taken to be any built up area from a village upwards.

DefinitionDefinitionUrban flooding: ‘An overflowing or irruption of a great body of water over land in a built up area which is not usually submerged’

Causes of urban floodingCauses of urban flooding

Pluvial flooding – unable to enter drainage systemPluvial flooding – ejection from drainage systemFluvial flooding – coastal or large watercourseFlooding due to asset performanceCo-incident flooding

Drainage systemsDrainage systemsWatercourses Watercourses -- may be culvertedmay be culverted

Combined sewerage systemsCombined sewerage systemsSurface water drainsSurface water drains

Area scalesArea scales

Flooding phasesFlooding phasesopen-channelflow:

dry terrain

empty pipes

pressurizedflowin pipes

interactionbetweentwo flows

onsurface

inpipes

beforerainfall:

hydraulic

gradient

Contributory factorsContributory factorsChanges in rainfallChanges in rainfallUrbanisation and urban Urbanisation and urban creepcreepImpact of asset Impact of asset deterioration and deterioration and rehabilitationrehabilitationChanges in local flood Changes in local flood pathways and urban pathways and urban formform

Asset PerformanceAsset Performance

BlockagesBlockagesCollapsesCollapsesSedimentationSedimentationPumping station Pumping station failurefailureHydraulic Hydraulic incapacityincapacity

Flooding relatedFlooding relatedresearch projectsresearch projects

Foresight future floodingForesight future floodingAUDACIOUSAUDACIOUSFRMRC 1FRMRC 1Bradford flood management enquiryBradford flood management enquiryNORIS NORIS –– No Rainwater In SewersNo Rainwater In SewersUWC UWC –– Urban Water CycleUrban Water Cycle3 Making Space for Water Pilots3 Making Space for Water PilotsERANET ERANET –– CRUECRUEUU UU –– Rainfall for climate change for sewerageRainfall for climate change for sewerageFRMRC 2FRMRC 2

FRMRC FRMRC -- www.floodrisk.org.ukwww.floodrisk.org.uk

Land Use ManagementLand Use ManagementReal Time Flood ForecastingReal Time Flood ForecastingInfrastructure ManagementInfrastructure ManagementTowards Whole System ModellingTowards Whole System ModellingUrban Flood ManagementUrban Flood ManagementStakeholder and PolicyStakeholder and PolicyGeomorphology, Sediments and HabitatGeomorphology, Sediments and HabitatRisk and UncertaintyRisk and Uncertainty

Sewer asset performanceSewer asset performance

Input Data & System Characteristics

HydraulicModelling

Asset PerformanceModelling

SedimentationHydraulic Inadequacy

CSOs &Storage

Blockage Pump Stations

Collapse

Hydraulic modellingHydraulic modelling

Integrate surface and subIntegrate surface and sub--surface surface hydraulic models. hydraulic models.

Surface flow modellingSurface flow modelling

Determine and quantify the urban Determine and quantify the urban flood flood ‘‘pathwayspathways’’

0 100 300 400x (m)544.0

izlivanjeInteractionInteraction(inflow & (inflow &

outflow)outflow)

Hydraulic Hydraulic model model outputoutput

Asset Performance ModellingAsset Performance Modelling

Regressional relationships based on Regressional relationships based on data on pipe assets and incident data on pipe assets and incident recordsrecordsPredict number of incidents rather Predict number of incidents rather than locationsthan locationsCurrently limited due to short Currently limited due to short datasets of sufficient qualitydatasets of sufficient quality

Blockage and Blockage and Collapse predictionCollapse prediction

y = 8.7868x-0.5659

R2 = 0.9318y = 16.0921x-0.6335

R2 = 0.8693y = 22.1198x-0.6269

R2 = 1.0000

0 250 500 750 1000

RV x Length (m5/3)

ICG 2-3

ICG 4+

y = 0.00881x0.72748

R2 = 0.95734y = 0.0126x1.4703

R2 = 1

0 2 4 6 8 10

Cover depth (m)

Pk ICG <= 4

Pk ICG > 4

Links to flooding eventsLinks to flooding events

From 15000 Blockage events From 800 Collapse incidents

Responses to deal Responses to deal with local floodswith local floods

Building form and operation Building form and operation (includes flood proofing)(includes flood proofing)Urban area form and Urban area form and operation (includes operation (includes sacrificial areas)sacrificial areas)Source controlSource controlAbove and below ground Above and below ground storagestorageOperation and maintenance Operation and maintenance of sewer systemof sewer system

Assessment of Assessment of Environmental & Public Health RisksEnvironmental & Public Health Risks

Principal risks in urban areaspathogen release from sewerage systemcontaminated sediments

Further urban researchFurther urban researchExamine the true socio economic cost Examine the true socio economic cost of urban flooding of urban flooding Develop a decision support toolDevelop a decision support toolComplete three Case StudiesComplete three Case Studies

CowesCowes

FRMRC FRMRC -- www.floodrisk.org.ukwww.floodrisk.org.uk

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