weir management as structural measures for flood reduction
TRANSCRIPT
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WEIR MANAGEMENT AS STRUCTURAL MEASURES
FOR FLOOD REDUCTION
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Contents
I. Introduction
What is weir? Weir formulas?
II. Approaches
Research Based Approach
Modelling Based Approach
III. Conclusion
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Weir -
Small overflow-type dam generally used to increase the level of a river or stream.
Introduction
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Weir Formula (for Mike 11)
I. Villemonte (Villemonte, 1947) formula for sharp crested weirs
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Weir FormulaII. Honma formula (we use this)
III. Extended Honma formula
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Dry Mode
Round Nosed Broad Crested Weir (free flow)
Weir Formulas (for ISIS)
Free Flow (we use this for ISIS)
Q = 0
Drowned Flow
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Research Based Approach
1st Solution – Cut Off the Crest
High Overflow
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Research Based Approach
2nd Solution – Adding Geotextile
High Overflow
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Research Based Approach
3rd Solution – Automated Gate
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Modelling approach
Define objectives1. Reduce downstream flooding
2. Find optimal heights for sediment equilibrium Calibrate MIKE11 against observed levels Build same model in ISIS Compare results using ‘multi-model
approach’
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Multi-model approach
Model is the sum of the experience of the person who wrote the code
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Reduce downstream flooding
No changes
0
20
40
60
80
100
120
140
0 5000 10000 15000 20000 25000 30000
ISIS
measured
Bed Level
MIKE11
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Reduce downstream flooding
Downstream weir removed
0
20
40
60
80
100
120
140
0 5000 10000 15000 20000 25000 30000
ISIS
measured
Bed Level
MIKE11
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Reduce downstream flooding
Four downstream weirs removed (1, 4, 5, 6)
0
20
40
60
80
100
120
140
0 5000 10000 15000 20000 25000 30000
ISIS
measured
Bed Level
MIKE11
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Reduce downstream flooding
Weirs removed and manning’s reduced
0
20
40
60
80
100
120
140
0 5000 10000 15000 20000 25000 30000
ISIS
measured
Bed Level
MIKE11
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Sediment transport
Meyer-Peter formula
qs related to q, s0, d50
steady-state model • Mean flow depth
• Mean channel width
• Mean velocity
• Channel Slope
• Particle diameter d50
http://ponce.sdsu.edu/onlinemeyerpeter.php
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Sediment transport
Results
qs (kg/sec/m) Qs (kg/sec) Weir No.
1.6 340 16
0.54 144 10
0 0 9
0 0 8
0.56 47 7
0.3 32.4 6
0 0 5
2.7 274 4
0.012 2.6 1
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Conclusions
MIKE11 results more sensitive to weir removal
Cannot conclude on effectiveness of weir removal due to model disagreement
Reduction of channel roughness better Proposals:
1. Vegetation clearance downstream
2. Alteration of weirs to improve sediment regime
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Sean and Ahmed who persistently work on Mike 11 and ISIS
Kim - our hydrological analysis expert
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Alex – Partially involved to Mike 11 and Hydrological Analysis.
Our report maker.
Stephane – our GIS expert
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Fazlul is working on Mike 11 and ISIS
Prima and Rajmund are working on Mike SHE report
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Amandine – our hydrological analysist & web designer
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Acknowledgment
Prof. Dr.-Ing. habil Klaus-Peter Holz as team 5 supervisor and his patience for assisting us during Hydroeurope 2010
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References
Wikipedia (2010). Weir. Wikipedia Foundation, Inc. http://en.wikipedia.org/wiki/Weir
White, Frank (2006). Fluid Mechanics. Mcgraw-Hill Education
Villemonte, James R. 1947. Submerged-Weir Discharge Studies, Engineering News. 1943. Engineering News Record, pp. 118-120. Record, pp. 54-57
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