flood forecasting and a case-study of the bristol avon · flood forecasting and a case-study of the...
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![Page 1: Flood Forecasting and a case-study of the Bristol Avon · Flood Forecasting and a case-study of the Bristol Avon BHS SW Young Hydrologist’s Meeting 25 October 2006 Andy Barnes,](https://reader034.vdocuments.us/reader034/viewer/2022051509/5aeb8b0a7f8b9a3b2e8e1bec/html5/thumbnails/1.jpg)
Flood Forecasting and a case-study of the Bristol Avon
BHS SW Young Hydrologist’s Meeting25 October 2006
Andy Barnes, Halcrow
![Page 2: Flood Forecasting and a case-study of the Bristol Avon · Flood Forecasting and a case-study of the Bristol Avon BHS SW Young Hydrologist’s Meeting 25 October 2006 Andy Barnes,](https://reader034.vdocuments.us/reader034/viewer/2022051509/5aeb8b0a7f8b9a3b2e8e1bec/html5/thumbnails/2.jpg)
Presentation Structure
• Flood Forecasting techniques• The Bristol Avon• Particular challenges• Model set-up• Inundation maps
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Flood Forecasting techniques
• Flood Intelligence Files (FIF’s)• Level-to-level correlations• Rainfall vs response analysis• Rainfall-runoff models• Hydrodynamic forecasting models
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Techniques: Flood Intelligence Files
Based on analysis of past events, including:• Peak levels/flows• Event rainfall information• Rate of rise & time-to-peak data• Typical response hydrographs
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Techniques: Level-to-level correlations
Site A
Site B
Peak level at Site B = f (Peak level at Site A)
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Techniques: Rainfall vs response analysis
Time
Flowor
level
T
Flood Warning threshold
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Techniques: Rainfall-runoff models
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Techniques: Hydrodynamic models
Inflow 1
Inflow 2
Inflow 3
Town
Forecast
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BA catchment: Location
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BA catchment: Main tributaries
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BA catchment: Topography
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BA catchment: Hydrology - SAAR
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BA catchment: Main flood risk areas
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BA catchment: October 2000 flood event
Approximate numberof properties flooded
• Bath 3
• Bradford-on-Avon 27
• Chippenham 3
• Malmesbury 22
• Trowbridge 1
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BA catchment: July 1968 flood event
Pensford, River Chew
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Challenges: Information
Challenges of flood forecasting model:
• Pilot study for hydrodynamic forecasting model
• Large catchment• 9 models• Tidal / fluvial interaction
And……………
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Challenges: Rating reviews
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Discharge (m3/s)
Stag
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Bye modelAgency ratingSpot gaugingsHalcrow ISISRecommended rating
Datum = 67.80m AOD
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Challenges: Structures
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Challenges: Netham Weir
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Challenges: Inundation maps
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Challenges: Upstream storage
Significant upstream storage in some catchments
e.g. Chew Valley Lake
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Model: Separate models
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Bitton
Dauntsey
Calstone
Startley
Fosseway
Hallatrow
Rodbourne
Semington
Chew Magna
Hawkeridge
Crabb Mill
MiddlehillAshton Vale Brislington
Ladden Bows
Stoke Bottom
Witham Friary
Matford Bridge
Midsomer Norton
Chipping Sodbury
Chew Valley Lake
Holwell
ChewStoke
Brokenborough
Frome
Calne
Vallis
Wellow
Midford
Stanley
Twerton
Bathford
Frenchay
Saltford
Avonmouth
Tellisford
Trowbridge
Wallbridge
ChippenhamNetham Weir
Tubbs Bottom
Compton Dando PulteneyWeir
Great Somerford
Bradfordon Avon
FramptonCotterell
Bath Ultrasonic
Middle Avon
Upper Avon
Lower Avon
River Chew
Midford Brook
Somerset Frome
Bristol Frome
River Biss
RiverMarden
Bristol Avon Flood Forecasting ModelCatchment map showing location ofseparate models and level/flow stations
# Error correction# Inflow# Monitoring
# Structure# Tidal
Level/Flow station type
Somerset FromeRiver BissRiver Marden
Upper AvonMiddle Avon
Midford BrookBristol FromeRiver ChewLower Avon
Model
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Model: Routing and hydrodynamic reaches
# Error correction# Inflow# Monitoring
# Structure# Tidal
Level/Flow station type
RoutingHydrodynamic
Model type
Bristol Avon Flood Forecasting ModelCatchment map showing location of routing andhydrodynamic models and level/flow stations
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Bitton
Dauntsey
Calstone
Startley
Fosseway
Hallatrow
Rodbourne
Semington
Chew Magna
Hawkeridge
Crabb Mill
MiddlehillAshton Vale Brislington
Ladden Bows
Stoke Bottom
Witham Friary
Matford Bridge
Midsomer Norton
Chipping Sodbury
Chew Valley Lake
Holwell
ChewStoke
Brokenborough
Frome
Calne
Vallis
Wellow
Midford
Stanley
Twerton
Bathford
Frenchay
Saltford
Avonmouth
Tellisford
Trowbridge
Wallbridge
ChippenhamNetham Weir
Tubbs Bottom
Compton DandoPulteneyWeir
Great Somerford
Bradfordon Avon
FramptonCotterell
Bath Ultrasonic
Middle Avon
Upper Avon
Lower Avon
River Chew
Midford Brook
Somerset Frome
Bristol Frome
River Biss
RiverMarden
![Page 24: Flood Forecasting and a case-study of the Bristol Avon · Flood Forecasting and a case-study of the Bristol Avon BHS SW Young Hydrologist’s Meeting 25 October 2006 Andy Barnes,](https://reader034.vdocuments.us/reader034/viewer/2022051509/5aeb8b0a7f8b9a3b2e8e1bec/html5/thumbnails/24.jpg)
Model: Conversion of existing models
• Existing models used where possible• HecRas to ISIS• Simplifications• Run-time & stability improvements
![Page 25: Flood Forecasting and a case-study of the Bristol Avon · Flood Forecasting and a case-study of the Bristol Avon BHS SW Young Hydrologist’s Meeting 25 October 2006 Andy Barnes,](https://reader034.vdocuments.us/reader034/viewer/2022051509/5aeb8b0a7f8b9a3b2e8e1bec/html5/thumbnails/25.jpg)
Model: Other info
• Gate control rules• Cross-section extension• Ungauged tributaries
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Model: Calibration and verification
Flows at Great Somerford - October 2000
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Flows at Great Somerford - January 2003
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Flows at Great Somerford - December 2000
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Model: NFFS
• NFFS ‘forecasting platform’• Delft• National consistency
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Maps: MIP areas
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Maps: Information
• Scenarios• Return period estimation• DeltaMapper• LiDAR data
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Maps: Example output
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Maps: Real-time inundation maps
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Questions……
Any questions?