Open Channel Flow Project Description of the Project A new road has recently been constructed in rural Victoria which has resulted in an embankment crossing XX Creek. During recent storms in the area,...

Open Channel Flow Project

Description of the Project

A new road has recently been constructed in rural Victoria which has resulted in an embankment crossing XX Creek. During recent storms in the area, sections of XX Creek upstream of the road embankment have been flooded, and residents have complained to the local authority that the road embankment is the cause of this flooding. The consulting engineers who designed the infrastructure for the road have defended their original design by noting that the local authority allowed urban development to take place in the catchment upstream of the road embankment.

You are employed in a consulting engineering firm, which was has been commissioned to investigate the impact of flooding in XX Creek. You have been asked by your supervising engineer to undertake an assessment of the water/environmental engineering issues that result from the works that have undertaken in the XX Creek catchment.

Task 4:

Determine a stage discharge relationship for the road crossing of XX Creek.

Using the runoff values estimated in the Catchment Analysis Project, determine a stage versus discharge relationship (rating curves) incorporating all the discharges from all the AEPs for XX Creek at the road crossing. This relationship will be used to determine the depth of flooding that will be expected at the road embankment. Rating curves should be produced for both rural and urban cases on a single plot.

The creek channel properties are approximated by the following equations and figure. Parameters for you are dependent on the 5th digit of your student number. If the 5th digit of your student number is an even number select ‘Case 1’, otherwise select ‘Case 2’. ‘0’ is considered as even number.

where, is the 3 hour rainfall intensity in mm/hr for x% AEP event. All these I values should be taken from the IFD rainfall intensity values in the Catchment Analysis Project.

The channel is a natural channel, with a clean winding main stream. There are some sections with shallow pools. The flood plain is predominantly composed of light brush and trees (both in summer and winter). Select appropriate Manning’s ‘n’ values for the sections from table provided and consider a worst case scenario.

Channel Cross-Section

Please be noted that, Yc is
not the critical depth, rather it is channel depth. The slope of the embankments on either side of the main channel and the flood plains are 1 Horizontal : 2 Vertical.

NOTE:

1. Any assumptions made in your calculations should be
clearly stated.

2. DO NOT USE your calculated “Q” and “I” values, rather use the values provided by me for your current calculations.

3. values used in your calculations should be clearly stated.

4. Show at least one sample calculation (including all equations with numbers clearly substituted) from each of the “Main channel flow only” case and “Flow in the floodplain” case.

5. Your final outputs MUST contain:

i) Graphs showing calculated discharges (Q) vs. calculated depths (y) for both ‘urban’ and ‘rural’ scenarios. Put depths in y-axis.

ii) Also, you MUST present the table below with the calculated values of depths:

6. Insert your final answers, graphs and sample calculations in a Word file. You don’t need to copy all the rows from your Excel calculation. Rather copy only the relevant (corresponding to your discharge) ‘y’ values and the rows with those values.

Task 5: Flood mitigation strategy

For the urban scenario (current condition), the authority wants to reduce the flood levels. As a mitigation strategy they are proposing to make the main channel bigger through making it a rectangular section having a width equals to the current top-width of the trapezoidal channel. The shape of the floodplains remains same. Calculate the following and comment on the differences in flood levels. If you find an unusual result, please specify the reason.