School of Civil EngineeringFACULTY OF ENGINEERING

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

Dr Andrew SleighDr 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 velocity1 m/s

• 1 in 200 year design flow 48 m3/s

• 1 in 1000 year design flow 242 m3/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 = 48m3/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 = 48m3/s

4. Time = Volume / Q

986 304 m3

10.62 m3/s

37.38 m3/s26386 seconds7 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 m3/s

• Maximum velocity on spillway 8 m/s

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

2/3actual 2

3

2HgBCQ d

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 = 242m3/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 45o

• 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/m2

inletinletinlet

rrr z

g

u

g

pz

g

u

g

p

22

22

gg

uzz

g

pp inlet

inletrr

inlet

2

2

225 130 N/m2

22

Today’s lecture:

• Design Study

• Used basic fluid mechanics seen in lectures

• Sized and checked design

• For more info: www.efm.leeds.ac.uk/CIVE/FluidLevel1/CaseStudies