bowston weir design discussion - scrt.co.uk

Bowston Weir – Design discussion

CBEC ECO ENGINEERING11/4/2017

Bowston WeirWeir Attributes

• River Slope approximately = 0.01m/m

• Weir Height = 3m

• Backwater effect 0.7.𝐷

𝑠= 210𝑚

• Observed backwater = 300m

• Weir width approximately = 38m

Nearby Structures/ attributes

• House immediately downstream on the right bank

o Set back approximately 5 m

o 4.6m m above channel bed

• Road adjacent to RHB 330m U/S of weir

• Power lines upstream of weir

Model overview – Existing ConditionsMODEL NODES

Stage Summary

59.00

60.00

61.00

62.00

63.00

64.00

65.00

66.00

67.00

68.00

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00

Sta

ge (

mA

OD

)

Realtive chainage (m)

Stage long profile

T2 - Maximum modelled water level (mAOD) T10 - Maximum modelled water level (mAOD)

T50 - Maximum modelled water level (mAOD) T100 - Maximum modelled water level (mAOD)

Velocity Summary

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00

Velo

city (

ms

-1)

Relative chainage (m)

Velocity long profile

T2 - Average modelled velocity at peak flow (ms-1) T10 - Average modelled velocity at peak flow (ms-1)

T50 - Average modelled velocity at peak flow (ms-1) T100 - Average modelled velocity at peak flow (ms-1)

Shear Stress Summary

0.00

50.00

100.00

150.00

200.00

250.00

300.00

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 900.00 1000.00

Shear

Str

ess (

nm

-2)

Axis Title

Shear Stress long profile

T2 - Shear Stress (nm-2) T2 - Shear Stress (nm-2) T2 - Shear Stress (nm-2) T2 - Shear Stress (nm-2)

Schematic of proposed design

Indicative design profile

Proposed bed regrading

and indicative location of

rock steps

Bowston Weir: Indicative schematic of bed regrading and rock

steps associated with “Full Removal” option

ReachLength between U/S and D/S hydraulic controls: 705mDrop in bed level: 3.99mChannel slope: 0.56%

Section to be regraded (vicinity of weir)Length: 310mDrop in bed level: 2.75Channel slope: 0.88%

Indicative visualisation

Concept visualisation: water levels and channel width to be adjusted following design stage