Modelling of the 2005 flood event in Carlisle
description
Transcript of Modelling of the 2005 flood event in Carlisle
![Page 1: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/1.jpg)
Modelling of the 2005 flood event in Carlisle
Jeff Neal1, Paul Bates1,
Tim Fewtrell, Matt Horritt, Nigel Wright, Ignacio Villanuaver, Sylvia Tunstall, Hazel Faulkner, Tom Coulthard, Jorge Ramirez, Caroline
Keef2, Keith Beven and David Leedal3
1School of Geographical Sciences, University Road, University of Bristol, Bristol. BS8 1SS.2JBA Consulting, South Barn, Broughton Hall, Skipton, N Yorkshire, BD23 3AE, UK.
3Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
![Page 2: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/2.jpg)
• Carlisle 2005 event data• Overview• Issues
• Inundation modelling• Channel hydraulics and gauges• Structural complexity• Resolution• New numerical scheme
• Beyond inundation modelling• Urban futures• Probabilistic flood risk at confluences
Introduction
![Page 3: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/3.jpg)
2005 event data
![Page 4: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/4.jpg)
2005 event data
![Page 5: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/5.jpg)
2005 event data
![Page 6: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/6.jpg)
Channel hydraulics and gauges
![Page 7: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/7.jpg)
1D/2D model complexity
![Page 8: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/8.jpg)
1D/2D model complexity
![Page 9: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/9.jpg)
Urban floodplain processes
Neal et al., 2009
25 m resolution10 m resolution5 m resolution
![Page 10: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/10.jpg)
A new LISFLOOD-FP formulation
• Continuity Equation• Continuity equation relating flow fluxes and change in cell depth
• Momentum Equation• Flow between two cells is
calculated using:
• Manning’s equation (ATS)
2
,1,,1,,
xQQQQ
th ji
yjiy
jix
jix
ji
xxzh
nhQ
2135
flow )(
i jhflow
i j
Representation of flow between cells in LISFLOOD-FP
xhqtnghxzhtghq
Qflowflow
flow
3/102 /1
![Page 11: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/11.jpg)
A new LISFLOOD-FP formulation
![Page 12: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/12.jpg)
A new LISFLOOD-FP formulation
![Page 13: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/13.jpg)
Probabilistic flood risk mapping at confluences
Q
RP
![Page 14: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/14.jpg)
Q
RP
Q
RP
Q
RP
The problem at confluences
? ?
![Page 15: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/15.jpg)
Set Δ of m gauges. Each is a random variable X at location i
Marginal distributions at each location Yi
Conditional distribution, spatial dependence
Simulate events over time t (e.g. 100 years) when y at Yi is greater than u
Sample from data at gauges Δ(Block bootstrapping)
The problem at confluences
• Model the conditional distribution of a set of variables given that one of these variables exceeds a high threshold.
Event simulation with spatial dependence
![Page 16: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/16.jpg)
Set Δ of m gauges. Each is a random variable X at location i
Marginal distributions at each location Yi
Conditional distribution (spatial dependence)
Simulate events over time t (e.g. 100 years) when y at Yi is greater than u
Sample from data at gauges Δ(Block bootstrapping)
The problem at confluences (uncertainty)
• Model the conditional distribution of a set of variables given that one of these variables exceeds a high threshold.
Refit to data and run event generator may times to approximate uncertainty
![Page 17: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/17.jpg)
Hydraulic modelling
4.0 4.5 5.0 5.5 6.0 6.5 7.0
45
67
89
10
Sheepmount
Model
Empi
rical
2.0 2.2 2.4 2.6 2.8 3.02.
02.
22.
42.
62.
83.
03.
2
Cummersdale
Model
Empi
rical
1.0 1.2 1.4 1.6 1.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Harraby Green
Model
Empi
rical
3.4 3.6 3.8 4.0 4.2 4.4
3.5
4.0
4.5
5.0
5.5
Linstock
Model
Empi
rical
3.0 3.5 4.0 4.5 5.0
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Great Corby
Model
Empi
rical
2.2 2.4 2.6 2.8 3.0 3.2 3.4
2.5
3.0
3.5
Greenholme
Model
Empi
rical
![Page 18: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/18.jpg)
Hydraulic modelling
• LISFLOOD-FP hydraulic model (Bates et al., 2010)• 1D diffusive channel model• 2D floodplain model at 10 m resolution• Model calibrated on 2005 flood event (RMSE 0.25 m).
![Page 19: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/19.jpg)
Hydraulic modelling
• LISFLOOD-FP hydraulic model (Bates et al., 2010)• 1D diffusive channel model• 2D floodplain model at 10 m resolution• Model calibrated on 2005 flood event (RMSE 0.25 m).
• Event simulation• 47000 events• Scaled 2005 hydrographs• Event simulation time was 0.1-2 hours• Analysis took 5 days and generated 40 GB of data
![Page 20: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/20.jpg)
Run 1 flood frequency• Run 1 of the event generator using all flow data
![Page 21: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/21.jpg)
Run 1 flood frequency
• The maximum flood outline was a combination of multiple events.
• Cannot assume same return period on all tributaries
![Page 22: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/22.jpg)
Uncertainty in the 1 in 100 yr flood outline
![Page 23: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/23.jpg)
Risk• MasterMap building outlines• Depth damage curve• Calculate damage from each event
![Page 24: Modelling of the 2005 flood event in Carlisle](https://reader036.fdocuments.net/reader036/viewer/2022081604/56816039550346895dcf5bff/html5/thumbnails/24.jpg)
Conclusions• Flooding at confluences is critical to the basin-wide development of
flood hazard and depends on the joint spatial distribution of flows.• Assuming steady state flows over predicted flood hazard for a range of
flows and event durations.• The maximum flood outline was a combination of multiple events.
• Cannot assume the same return period on all tributaries• Risk assessment using the event data was demonstrated.
• Expected damages increase nonlinearly. • As expected a few events caused most of the damage.