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

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Oct 24, 2013 (3 years and 11 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



For more info:

www.efm.leeds.ac.uk/CIVE/FluidLevel1/CaseStudies