# Lecture 14: Design Study 2 Millwood & Gaunless Flood Alleviation Schemes

Mechanics

Oct 24, 2013 (4 years and 8 months ago)

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School of Civil Engineering

FACULTY OF ENGINEERING

Lecture 14: Design Study 2

Millwood & Gaunless Flood Alleviation
Schemes

Dr Andrew Sleigh

Dr Cath Noakes

www.efm.leeds.ac.uk/CIVE/FluidsLevel1

Gaunless

Flood Alleviation Scheme

Design Study 2

Gather data

Sketch layout

marking levels

Marking areas where volume calcs required

Draw a cross section

Identify levels in each region

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Question 1 Data Required

Culvert Diameter

2.6 m

Number of culverts

2

Maximum culvert velocity

1 m/s

1 in 200 year design flow

48 m
3
/s

1 in 1000 year design flow

242 m
3
/s

Gaunless

Flood Alleviation Scheme

Design Study 2

Steps

1.
Calc volume in rise from 123 to 127 m

2.
Calc flow in culverts (Q=Av)

i.e. Flow out of the reservoir

3.
Calc net inflow, Q = Qin

Qout

Qin = 48m
3
/s

4.
Time = Volume / Q

Gaunless

Flood Alleviation Scheme

Design Study 2

Steps

1.
Calc volume in rise from 127 to 127 m

2.
Calc flow in culverts (Q=Av)

i.e. Flow out of the reservoir

3.
Calc net inflow, Q = Qin

Qout

Qin = 48m
3
/s

4.
Time = Volume / Q

986 304 m
3

10.62 m
3
/s

37.38 m
3
/s

26386 seconds

7 hours 20mins

Gaunless

Flood Alleviation Scheme

Design Study 2

The Spillway

Gaunless

Flood Alleviation Scheme

Design Study 2

Limiting velocity down spill way

Design for 1000 year flood gives 8m/s

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Gaunless

Flood Alleviation Scheme

Design Study 2

Question 2 Data

Spillway weir Cd

0.73

Spillway weir width

150 m

1 in 1000 year design flow

242 m
3
/s

Maximum velocity on spillway 8 m/s

Assume velocity on spillway is 4 times the
velocity over the weir

Gaunless

Flood Alleviation Scheme

Design Study 2

Steps

1.
Calc allowable velocity over weir

2.
Calc height

Use Q = Av = BHv

3.
Calc height for a 1000 year flood

Q = 242m
3
/s

4.
Calc Velocity over weir

0.861 m

2.0 m/s

0.5 m

1.96 m/s

Gaunless

Flood Alleviation Scheme

Design Study 2

Diversion of culvert

Gaunless

Flood Alleviation Scheme

Design Study 2

Question 3 Data

Water level above bend

13m

Flow velocity

1 m/s

Diameter

2.6m

Reduces to diameter

1.5m

Bend angle

45
o

Assume atmospheric pressure 10m water

Gaunless

Flood Alleviation Scheme

Design Study 2

Steps

1.
Calc inlet pressure

2.
Follow steps as in lecture examples

402 kN/m
2

225 130 N/m
2

22

Today’s lecture:

Design Study

Used basic fluid mechanics seen in
lectures

Sized and checked design