WEIR MANAGEMENT AS STRUCTURAL MEASURES

FOR FLOOD REDUCTION

Contents

I. Introduction

What is weir? Weir formulas?

II. Approaches

Research Based Approach

Modelling Based Approach

III. Conclusion

Weir -

Small overflow-type dam generally used to increase the level of a river or stream.

Introduction

Weir Formula (for Mike 11)

I. Villemonte (Villemonte, 1947) formula for sharp crested weirs

Weir FormulaII. Honma formula (we use this)

III. Extended Honma formula

Dry Mode

Round Nosed Broad Crested Weir (free flow)

Weir Formulas (for ISIS)

Free Flow (we use this for ISIS)

Q = 0

Drowned Flow

Research Based Approach

1st Solution – Cut Off the Crest

High Overflow

Research Based Approach

2nd Solution – Adding Geotextile

High Overflow

Research Based Approach

3rd Solution – Automated Gate

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’

Multi-model approach

Model is the sum of the experience of the person who wrote the code

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

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

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

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

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

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

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

Sean and Ahmed who persistently work on Mike 11 and ISIS

Kim - our hydrological analysis expert

Alex – Partially involved to Mike 11 and Hydrological Analysis.

Our report maker.

Stephane – our GIS expert

Fazlul is working on Mike 11 and ISIS

Prima and Rajmund are working on Mike SHE report

Amandine – our hydrological analysist & web designer

Acknowledgment

Prof. Dr.-Ing. habil Klaus-Peter Holz as team 5 supervisor and his patience for assisting us during Hydroeurope 2010

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