In Rivers Practicals 2 and 3 you undertook a surveying exercise across an urban stream on the Macquarie University campus. You then processed this data and used the discharge and velocity equations to analyse and quantify the flow velocity and discharge characteristics for this stream. You will be using the skills learnt in these practicals (and the lecture on Stormflow) in this assignment.
In this assignment you will:
1) use the information provided below to undertake calculations of flow velocity and discharge for the channel cross section provided and using three different roughness (Manning’s n) values.
2) research the scientific literature using your library database skills to investigate urban stream restoration approaches and their effects on stream flow and storm flow (hydrology). At least 10 scientific references should be used in your assignment including the compulsory reading, Chin et al.(2013)
3) write a scientific report. Only the scientific report is to be handed in to Turn It In. Do not hand in this assignment information and calculation sheet. The Data and Calculations section below should be written up (transferred) to the results section of your report (see section below on report structure).
Data and calculations – urban stream cross section and hydrology
Figure 1 shows a cross section of an urban stream. You will use this cross section to calculate flow velocity and discharge for a range of different roughness (Manning’s n) scenarios.
Flow velocity equation
V = [(D2/3) x (S1/2) / n], where
V = mean channel velocity (m/s)
D = flow depth (m)
S = water surface slope (m/m; often approximated by the slope of the bed)
n = Manning’s roughness coefficient
discharge = velocity x cross-sectional area
Q = V x A, where
Q = discharge (m3/s)
V = velocity (m/s)
A = cross-sectional area (m2)
Using this channel cross-section, complete Table 1. Channel slope has been provided for you. This table will need to be reproduced as part of the results section of your scientific report.
Table 1 Hydrology of an urban stream at Macquarie University
|Channel slope||0.005 m/m|
|Bankfull channel depth|
|Bankfull channel width|
|Channel cross sectional area|
Three different Manning’s n roughness parameters have been provided in Table 2. Use these to calculate the flow velocity and discharge for scenarios 1, 2, and 3. This table will need to be reproduced as part of the results section of your scientific report.
Table 2 Roughness scenarios, flow velocity and discharge characteristics of an urban stream at Macquarie University
|Manning’s n roughness for scenario 1 (smooth stormwater pipe)||0.007|
|Manning’s n roughness for scenario 2 (moderate in-channel vegetation)||0.07|
|Manning’s n roughness for scenario 3 (woody debris and dense in-channel vegetation)||0.3|
|Flow velocity for scenario 1|
|Flow velocity for scenario 2|
|Flow velocity for scenario 3|
|Discharge for scenario 1|
|Discharge for scenario 2|
|Discharge for scenario 3|
The assignment questions
1) As part of the introduction – What are the characteristics of stream flow (hydrology) in urban environments?
2) As part of the results – Using the results of your calculations, explain how changing roughness impacts on stream flow hydrology in an urban stream?
3) As part of the discussion – Assume that the aim of urban stream restoration is to reduce flow velocity to improve public safety, minimise sediment erosion and improve physical structure (i.e. geomorphology). What types of restoration/rehabilitation can be undertaken to achieve these aims? [Hint: read Chin et al. (2013) and take a walk around campus for examples (Mars Creek behind Y3A, University Creek between Research Park Drive and Innovation Rd)].
4) As part of the discussion – What might be some additional benefits of undertaking urban stream restoration (e.g. on stream ecology and/or water quality)?