School of Civil Engineering FACULTY OF ENGINEERING Lecture 14: Design Study 2 Millwood & Gaunless Flood Alleviation Schemes Dr Andrew Sleigh Dr Cath Noakes

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 culverts2 Maximum culvert velocity1 m/s 1 in 200 year design flow48 m 3 /s 1 in 1000 year design flow242 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 m m 3 /s m 3 /s 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 Cd0.73 Spillway weir width150 m 1 in 1000 year design flow242 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 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 bend13m Flow velocity1 m/s Diameter2.6m Reduces to diameter1.5m Bend angle45 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 N/m 2

22 Today’s lecture: Design Study Used basic fluid mechanics seen in lectures Sized and checked design For more info: