River Kelvin Case Study

Steady Flow Analysis Theory 1D Steady Flow Modelling

Geometrical data River cross-sections + distance between them.

∆x

Q

h

Hydraulic structures 1D Steady Flow Modelling

Equation v 2 v 2 z + y +α 1 = z + y +α 2 + ∆E 1 1 1 2g 2 2 2 2g

+ = z1 y1 water level v = mean veloc ity v = Q / A Solution α = the energy coefficien t ∆E = energy loss between sections 1 and 2 Standard step method. Q

1 2 Z + y ∆x 1D Steady Flow Modelling

Boundary Conditions Upstream – constant inflow. Q Downstream – known water level.

T

Q

h h

T Q 1D Steady Flow Modelling

Prediction Water level at each cross-section. ∆x

Q

h

Advantages Easy to predict maximum water level. River Kelvin Case Study

Steady Flow Analysis Case Study River Kelvin Case Study

The December 1994 Flood

Rainfall event with a return period between 1 in 300 and 1 in 1000 years.

Flood return periods • Lower River Kelvin 1 in 200 years. •Main tributaries - and 1 in 50 years.

Flood outline 9 to 11 th December 1994 River Kelvin Case Study

Consequences Catastrophic flood which caused: • Damage estimated at £10 million. • Extensive damage to over 300 business and residential properties. •The loss of two lives.

Inundation in

Flooding of McNair’s Factory

Overtopping of flood defences at River Kelvin Case Study

Solution Options considered: • Flood storage – discounted due to timing of flood peaks. • Channel dredging – discounted due to environmental damage and increased flood peaks downstream in .

Solution adopted was a system of direct defences using earth embankments and retaining walls, the location of which was chosen to preserve as much of the existing flood plain as practical. River Kelvin Case Study

Solution

Examples of the direct defences used of the River Kelvin flood defence scheme. River Kelvin Case Study

Steady Flow Analysis The Task River Kelvin Case Study

Model Calibration The HEC-RAS model provided has been set up with: •Gauged inflows for the River Kelvin and its tributaries for the December 1994 flood, Table 1. •A rating curve downstream boundary based on uniform flow. •Manning’s ‘n’ values of 0.02 and 0.01 on the flood plain and main channel respectively.

Calibrate the model by altering the Manning’s ‘n’ values to obtain a reasonable agreement ± between the observed results provided in Table 2 and the computed values. River Kelvin Case Study

Flood modelling •Use the calibrated model to estimate flood levels for the 50, 100 and 200 year flood events, inflow data is provided in Table 3. •Determine the maximum defence levels for a flood prevention scheme for Kirkintilloch. River Kelvin Case Study

Reporting The case study report should include: •A map showing the location liable to flooding for a return period of 1 in 200 years. •Details of required flood defence levels in the location of Kirkintilloch.