Importance of Land use management on the Flood Management in the Chi River Basin, Thailand Kittiwet...
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Transcript of Importance of Land use management on the Flood Management in the Chi River Basin, Thailand Kittiwet...
Importance of Land use management on the Flood Importance of Land use management on the Flood Management in the Chi River Basin, ThailandManagement in the Chi River Basin, Thailand
Kittiwet KuntiyawichaiKittiwet Kuntiyawichai
Bart Schultz
Stefan Uhlenbrook
F.X. Suryadi
Ann van Griensven
44thth International Symposium on Flood Defence International Symposium on Flood Defence
6 – 8 May 2008, Toronto, Canada
• Problem definition
• Objectives of the study
• Model setup
• Introduction
ContentsContents
• Conclusions & Recommendations
• Discussions
• SWAT & 1D/2D SOBEK simulations
IntroductionIntroduction
• Area = 49,47749,477 km2
• Main system: Chi River, Chi River, 765 km river length
•Population = 6.9 million6.9 million people
• Sub-basins: 2020
• Land use: 60%60% (30,000 km2) = agricultural land• Precipitation: 1,2001,200 mm/year
• Potential evaporation: 1,2901,290 mm/year
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Chi River Basin
Model simulationsModel simulations
IntroductionIntroduction
Selection as a test area based on the availability of input data
results will be applied & provide benefit to the whole Chi River Basin at later stage
Study area: Study area: Yang River BasinYang River Basin
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
IntroductionIntroduction
• Area = 4,1454,145 km2
• Land use: 8383%% (3,440 km2) = Agricultural land (Paddy field)
• Major flood events: 19781978 entire Chi River Basin
19801980 in the Yang River Basin
• Sub-basins: 55
Yang River BasinYang River Basin
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Problem definitionProblem definitionLarge flood in 2001 Large flood in 2001 Precipitation = 315315 mm/3 days
Stagnant & urban flooding
‘‘How will the ongoing changes in land use, water management & flood How will the ongoing changes in land use, water management & flood protection influence floods & flooding, and what would be the protection influence floods & flooding, and what would be the implications for flood management?’implications for flood management?’
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Objectives of the studyObjectives of the study
‘To identify both structural & non-structural measures in order to reduce flood impacts to settlements in the Yang River Basin’
Under Under different scenariosdifferent scenarios:
Storage improvement
Land use management changes
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Model setupModel setup
• Hydrologic model (SWAT)Hydrologic model (SWAT) calculate a tributary inflow at all the selected points on the river system.
• Hydraulic model (1D/2D SOBEK)Hydraulic model (1D/2D SOBEK) simulate the flow of water through a river channel network & create flood inundation
extents for the specified return periods.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Model setupModel setup
Relationship between SWATSWAT & 1D/2D SOBEK,1D/2D SOBEK, & the physical aspects
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Calibration resultsCalibration results
Calibration period: 1/6/2001-31/10/20011/6/2001-31/10/2001
SWAT simulationsSWAT simulationsIntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Calibration accuracy:
SWAT simulationsSWAT simulations
Table:Table: Calculated areal rainfallareal rainfall & peak peak dischargesdischarges for various return periods (ignoring flooding).
SWATSWAT calculate a tributary inflow on the Yang River for different return periods.
Observed rainfall for each station (4 stations) converted into areal rainfall (Thiessen method) & used as input to SWATSWAT.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
1D SOBEK calibration results1D SOBEK calibration results
• Calibration period 1/6/2001-31/10/20011/6/2001-31/10/2001
• Calibration parameter Manning’s roughnessManning’s roughness
1D/2D SOBEK simulations1D/2D SOBEK simulationsIntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
1D/2D SOBEK simulations1D/2D SOBEK simulations
Natural flood storageNatural flood storageTarget: arbitrarily set to limit a 100-year100-year incident event to a 10-year10-year target peak flow.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
1D/2D SOBEK simulations1D/2D SOBEK simulations
The modelled flood extentsThe modelled flood extents
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
1D/2D SOBEK simulations1D/2D SOBEK simulations
Possible natural flood storagePossible natural flood storage
Basis: considering the simulated simulated 100-year flood level100-year flood level in relation to the topographic condition at the locations where the floodwater needed to be released to reduce
flood risk downstream.
11
22
33
Starting risk location
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
1D/2D SOBEK simulations1D/2D SOBEK simulations
Possible natural flood storagePossible natural flood storage
Peak discharge reduced with the magnitude close to the 10-year event.
Comparison between the simulated 100-year discharge with/without flood retention for the same section of the downstream river channel.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
DiscussionsDiscussions• The methodology used to investigate the flood management measures
Numerical modelling of inundation processes at the floodplains.
• SWATSWAT calculate the tributary inflow to the Yang River.
• Calibration results SWAT SWAT is able to simulate the discharge reasonably. However, further calibration efforts for longer period &
model validation are required to obtain more accurate/reliable results.
• 1D/2D SOBEK1D/2D SOBEK predict flooding behaviour within a river system for different flood magnitudes.
• 1D/2D SOBEK1D/2D SOBEK simulation outputs it seems viable to provide enough flood storage to limit 100-year event to 10-year target peak flow by using
the natural floodplain.
• 3 flood storages3 flood storages ++ flood diversion channelflood diversion channel were identified by considering the calculated 100-year flood level in relation to the
topographic condition upstream of the risk location The simulated 100-year peak discharge was reduced only about 3.5% with the magnitude
close to the 10-year target peak flow.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
ConclusionsConclusions
• Coupling of SWAT & 1D/2D SOBEKSWAT & 1D/2D SOBEK is being developed to enable a better modelling of the actual physical behaviour & processes.
• Storage improvement Storage improvement options have been formulated as proposed flood management scheme. A step towards land use & management land use & management scenarios.
• 1D/2D SOBEK1D/2D SOBEK is found capable of simulating flood events with/without flood mitigation measures & delivering reliable results. Moreover:
It can provide the maximum inundation level, which is predominant for determining the damage at downstream risk location.
A sustainable method of flood risk management can also be established at later stage, which will be a useful component additionally to conventional flood defences in the Chi River Basin.
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
RecommendationsRecommendations
Future study will consider:Future study will consider:
• Areas that could not be used for storage Built-up area, i.e. urban, towns, villages (to minimize damage).
• Buffer zone to protect the built-up area from flooding.
• Full operation of flood detention basins, with many levels of floodwater sub-diversions, based on different floodwater levels.
• Examine the economic impacts for land within the assumed flood extent for flood storage by:
Categorize the land use types with respect to elevation
Define the cost for each land use type
Estimate an inundated area (incl. damage) per land use type
IntroductionIntroduction
ObjectivesObjectives
Problem definitionProblem definition
Model setupModel setup
DiscussionsDiscussions
RecommendationsRecommendations
ConclusionsConclusions
Model simulationsModel simulations
Thank youThank youThank you for your attentionThank you for your attention