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
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
Number of culverts
Maximum culvert velocity
1 in 200 year design flow
1 in 1000 year design flow
Gaunless Flood Alleviation Scheme
2.6 m
2
1 m/s
48 m3/s
242 m3/s
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
986 304 m3
2. Calc flow in culverts (Q=Av)

i.e. Flow out of the reservoir
10.62 m3/s
3. Calc net inflow, Q = Qin – Qout

Qin = 48m3/s
37.38 m3/s
4. Time = Volume / Q
Gaunless Flood Alleviation Scheme
26386 seconds
7 hours 20mins
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
Qactual
2
 Cd B 2 g H 3 / 2
3
• 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
2.0 m/s
2. Calc height

Use Q = Av = BHv
0.861 m
3. Calc height for a 1000 year flood

Q = 242m3/s
0.5 m
4. Calc Velocity over weir 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
Flow velocity
Diameter
Reduces to diameter
Bend angle
13m
1 m/s
2.6m
1.5m
45o
• Assume atmospheric pressure 10m water
Gaunless Flood Alleviation Scheme
Design Study 2
Steps
1. Calc inlet pressure
2
pinlet uinlet
pr ur2
  zr 

zinlet
g 2 g
g 2 g
pinlet
2
 pr

uinlet
 g
 
zr zinlet  
2g 
 g
225 130 N/m2
2. Follow steps as in lecture examples
402 kN/m2
Gaunless Flood Alleviation Scheme
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
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