WEIR MANAGEMENT AS STRUCTURAL MEASURES FOR FLOOD REDUCTION

Contents

I.

II.

Introduction What is weir? Weir formulas?

Approaches Research Based Approach Modelling Based Approach III. Conclusion

Introduction

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

Weir Formula (for Mike 11)

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

Weir Formula

II. Honma formula (we use this) III. Extended Honma formula

Weir Formulas (for ISIS)

Dry Mode Q = 0 Free Flow (we use this for ISIS) Drowned Flow Round Nosed Broad Crested Weir (free flow)

Research Based Approach

1 st Solution – Cut Off the Crest High Overflow

Research Based Approach

2 nd Solution – Adding Geotextile High Overflow

Research Based Approach

3 rd Solution – Automated Gate

Modelling approach

 1.

2.

Define objectives Reduce downstream flooding 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

140  No changes 120 100 80 60 40 20 0 0 5000 10000 15000 20000 25000 ISIS measured Bed Level MIKE11 30000

Reduce downstream flooding

140  Downstream weir removed 120 100 80 60 40 20 0 0 5000 10000 15000 20000 25000 ISIS measured Bed Level MIKE11 30000

Reduce downstream flooding

140  Four downstream weirs removed (1, 4, 5, 6) 120 100 80 60 40 20 0 0 5000 10000 15000 20000 25000 ISIS measured Bed Level MIKE11 30000

Reduce downstream flooding

 Weirs removed and manning’s reduced 140 120 100 80 60 40 20 0 0 5000 10000 15000 20000 25000 ISIS measured Bed Level MIKE11 30000

Sediment transport

Meyer-Peter formula

q s related to q, s 0 , d 50 steady-state model

• Mean flow depth • Mean channel width • Mean velocity • Channel Slope • Particle diameter d 50 http://ponce.sdsu.edu/onlinemeyerpeter.php

Sediment transport

 Results

qs (kg/sec/m)

1.6

Qs (kg/sec)

340 0.54

0 144 0 0 0.56

0.3

0 2.7

0.012

0 47 32.4

0 274 2.6

Weir No.

16 10 9 4 1 8 7 6 5

Conclusions

  MIKE11 results more sensitive to weir removal Cannot conclude on effectiveness of weir removal due to model disagreement  Reduction of channel roughness better  1.

2.

Proposals: Vegetation clearance downstream Alteration of weirs to improve sediment regime

Kim - our hydrological analysis expert Sean and Ahmed who persistently work on Mike 11 and ISIS

Alex – Partially involved to Mike 11 and Hydrological Analysis. Our report maker.

Stephane – our GIS expert

Prima and Rajmund are working on Mike SHE report Fazlul is working on Mike 11 and ISIS

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