Reference no: EM133046551

C&ENVENG 3077 Engineering Hydrology - The University of Adelaide

DESIGN PROJECT

Objective

Gain an in-depth understanding of how and when to apply different methods of obtaining design flows in a realistic context. Much of the learning will take place while working on this project, and it is expected that students consult with the teaching staff during formal contact and student consulting hours.

Introduction

The Inverbrackie Creek catchment is a small rural catchment with 19 years of gauged flow. The creek is an upper tributary of the Onkaparinga River located near Adelaide, South Australia, as shown in Figure 1. It is located upstream of Mt. Bold reservoir, which supplies much of Adelaide's potable water. The catchment experiences cool, wet winters and hot, dry summers with the majority of rain in May to August. The catchment is shown in more detail in Figures 2 to 4. Higher quality version of these maps are available for download from MyUni\Design project Information. The creek is in a region of gentle rolling hills with a narrow flood plain. An aerial photo of the catchment is shown in Figure 5; typical photos of the catchment are shown in Figures 6 to 10 (the colour photos are best viewed on the files provided in MyUni).

Department of Planning, Transport and Infrastructure (DPTI) is planning to replace the bridge crossing Inverbrackie Creek closest to the gauging station (Figure 3). This area is a part of the proposed gold mine development for the Woodside Area. In order to choose an appropriate design level for the bridge, the 1 in 10 and 1 in 100 year floods need to be calculated at the gauging station. In addition, mineral deposits have been discovered in the catchment and it is proposed construct a drift mine to access and extract the ore body.

You have been commissioned to:

(i) Obtain the 1:10 and 1:100 year design flows in the creek at the gauging station. Multiple estimates should be obtained using different methods (Phases 1 and 2). The methods and resulting estimates should be evaluated critically in order to choose the most appropriate design flow estimates;

(ii) Design a stormwater drainage scheme for part of the proposed mine site (Phase 3).

DESIGN PROJECT - PHASE 1

Objective

Obtain the design flows with AEPs of 1 in 10 year (10%) and 1 in 100 year (1%) at the gauging station of Inverbrackie Creek using several methods for peak flow estimation, including:
• At-site flood frequency analysis using FLIKE with the observed data only to estimate the peak flows
• Regional Flood Frequency Estimation techniques from ARR2016
• Probabilistic Rational Method using the regional approach for estimating the time of concentration
• [Masters only] More advanced techniques for peak flow estimation

Tasks
1. Provide an overview of the hydrological characteristics of the Inverbrackie Creek Catchment. (8 marks)
• Examine the seasonality of rainfall and flow/runoff by creating a plot of average monthly values
• Examine the inter-annual variability of rainfall and flow/runoff by creating a time series of annual rainfall/runoff
• Comment on the key trends from the hydrological characteristics
• Include any other information on the catchment (land-use, vegetation) that might impact on flood characteristics

Hints
1. See "MyUni\Phase 1 - Peak Flow Estimation\Design Project Data and Information" for daily time series of flows and rainfall that will be useful for this analysis
2. Use Excel's Pivot-tables - see "MyUni\Phase 1 - Peak Flow Estimation\Resources\Software: Using Pivot-tables"
3. Convert flow from units of ML to runoff with units of mm (by dividing by catchment area) to enable direct comparison with rainfall with units of mm
3. Google Earth has some great spatial visualisation tools - see "MyUni\Phase 1 - Peak Flow Estimation\Design Project: Data and Information" for a kml file of catchment that can be viewed in Google Earth

2. Extract and examine the annual series of peak flows from the daily flow data provided on MyUni. (7 marks)
• Identify any years with missing daily data
• Develop strategies to minimise the impact of missing data on the annual series of peak flows
• Plot an annual time series of the peak flows. Comment on the trends
• Produce a lognormal probability plot of the annual series of peak flows. Comment on the trends

Hints
1. Use Excel's Pivot-tables - see "MyUni\Phase 1 - Peak Flow Estimation\Resources\Software: Using Pivot-tables"
2. For tips on using probability plots, see "MyUni\Phase 1 - Peak Flow Estimation\Resources\Producing and Interpreting Probability Plots"

3. Complete FLIKE Self-Training Example Three -

• Provide a probability plot from the flood frequency analysis to indicate the uncertainty in the 1:100 year flows. Use log-normal and Gumbel scales (two plots). Comment on the model fit to observed data.
• Provide a table of design flows for AEPs (1 in Y year) of 2, 5, 10, 50 and 100 years. Comment on their uncertainty.
4. Undertake Flood Frequency Analysis using FLIKE and the annual series of peak flows from Task 2. (8 marks)
• Fit the LP3 and Gumbel probability models
• Provide the probability plot that shows the gauged data, the fitted flood frequency distribution and probability limits. Consider providing multiple plots with different y-axis and/or probability scales to show high and low peak flows. Comment on the fit of the flood frequency distribution to the gauged data.
• Provide a table of design flows for AEPs (1 in Y year) of 2, 5, 10, 50 and 100 years. Comment on key features of the design flows and their uncertainty

5. Use Regional Flood Frequency Estimation (RFFE) to estimate design flows with AEPs (1 in Y year) of 2, 5, 10, 50 and 100 years. (4 marks)
• Describe the key inputs used to obtain these estimates.
• Comment on the key differences from the estimates of design flows obtained in Task 4.

Hint: To use RFFE see "MyUni\Phase 1 - Peak Flow Estimation\Resources\Software: Regional Flood Frequency Estimation"

6. Use the probabilistic rational method to estimate the 1:10 and 1:100 year AEP design flows. Use regional methods to obtain the time of concentration. Describe the key inputs used to obtain these estimates. (4 marks)

7. [optional / not-marked in 2020] Trial two or more advanced procedures in FLIKE to improve design flow estimates.
• Describe the advanced method(s)
• Provide details of applying them to Inverbrackie Creek
• Report the fitted flood frequency distribution(s), including the design flow estimates and their uncertainty

8. Compare and discuss differences between the multiple estimates of the 1:10 and 1:100 year floods obtained in Tasks 4-6 (4-7 is optional in 2020). Select an estimate of design flow and justify your choice. (6 marks)
• Provide a table/graph which compares the design flow estimates
• Include a comparison of the corresponding uncertainties (where applicable)
• Outline the differences between them and potential reasons for differences
• Make a decision on which estimates you would choose and justify your choice

DESIGN PROJECT - PHASE 2

Objective
Obtain the 1:10 and 1:100 year design flows at the gauging station of Inverbrackie Creek using the runoff-routing model RORB.

This work will involve the development and calibration of the RORB model for the Inverbrackie Creek catchment, as well as its application to obtain the required design flows. In addition, the calibrated RORB model is to be used to assess the impact of the stormwater runoff from the proposed mine site on the 1:100 year design hydrograph at: (i) the point where stormwater from the mine site is discharged into Inverbrackie Creek, and (ii) the gauging station.

The final task in this phase is to compare and contrast the multiple estimates of design flows at the Inverbrackie Creek gauging station.

Tasks

1. RORB model development (calibration and validation):
(i) Division of catchment into appropriate sub-areas and identification of nodes
(ii) Development of RORB catchment file for calibration (fit) runs
(iii) Selection of storm events (rainfall and corresponding runoff data) for calibration and validation
(iv) Determination of the "best" RORB model parameters (i.e. model calibration)
(v) Testing (validation) of the calibrated RORB model
(vi) [Masters only] - undertake split-sample validation (where you switch the calibration and validation periods and re-do the analysis) and comment on the results

2. Determination of 1:10 and 1:100 year design flows at gauging station, including the impact of the mine site (25% of the marks)
(i) Appropriate alteration of RORB catchment file
(ii) Input of appropriate IFD data for Inverbrackie Creek catchment
(iii) RORB design runs for 10 and 100 year return periods. At a minimum, this should be done for a range of design durations and temporal patterns as specified in ARR, but potentially could include Monte Carlo Analysis on a wider range of inputs for the design runs
(iv) Choice of 1:10 and 1:100 year design hydrographs and peak flows
(v) Determination of impact of mine site on 1:100 year design hydrograph at discharge point and gauging station. This will require:
(a) Appropriate alteration of RORB catchment file
(b) RORB design runs for 100 year return period for a range of design durations and temporal patterns
(c) Comparison to results without the mine site

3. Recommend design flows based on all methods
Objective is to compare and contrast the methods used to obtain the 1:10 and 1:100 year design flows at the Inverbrackie Creek gauging station, as well as the actual design flows. The aim is to recommend final values of the 1:10 and 1:100 year design flows.
Five methods have been used in Phases 1-2 to estimate the design flows for Inverbrackie Creek.
• At-site Flood Frequency Analysis (LPIII and Gumbel probability models)
• Regional Flood Frequency Estimation (RFFE)
• Probabilistic rational method (regional tc)
• Advanced Flood Frequency Analysis (optional in 2020)
• RORB (Calibrated parameters)

(i) Identify and critically analyse the implications of the assumptions in each method (at least two assumptions per method)
(ii) Compare and contrast the different methods using relevant criteria (including but not limited to accuracy of results and ease of use)
(iii) Recommend design values for 1:10 and 1:100 year return periods and discuss reasons for this choice in the context of the design project.

The main body of the report (excluding cover sheet/title page and appendices) has a page limit of 24 pages. The report should be of professional quality and follow the course guidelines for report writing. Any pages beyond this limit will not be marked.

The quality of the report will be considered (15% marks) with reference to
• Spelling and grammar
• Structure and organisation
• Completeness
• Clarity and readability

DESIGN PROJECT - PHASE 3

Objective

Choose an appropriate site layout and design a stormwater drainage scheme for the proposed mine site.

Introduction

The location of the proposed Inverbrackie drift mine is shown on the map below. As part of the mine, the mineral deposit will be accessed via a horizontal tunnel that will be dug into the side of the hill at the site of the proposed mine entrance.

Tasks

1. Select the final location, layout and appropriate stormwater drainage scheme of the part of the mine site.

The following components should be considered:
(i) Administration building (approx. area = 7,500 m2)
(ii) Lawn (approx. area = 2,500 m2)
(iii) Car park (approx. area = 7,500 m2)
(iv) Paved area surrounding mine drift entrance (approx. area = 30,000 m2)
(v) Paved plant (machinery) area (approx. area = 15,500 m2)

The layout needs to take into account the following constraints:
(i) The area surrounding the mine drift entrance must cater for access to the tunnel
(ii) The car park and lawn area must be adjacent to the administration building.
(iii) The plant area must be adjacent to the mine drift.

When choosing an appropriate stormwater drainage scheme, the following needs to be considered
(i) The scheme shall identify appropriate sub-areas and appropriate locations for all pits and pipes.
(ii) When selecting pipe locations, keep in mind that the slopes of the pipes should match those of the ground surface as closely as possible to minimise construction costs.
(iii) All stormwater from the site and from those parts of the surrounding bushland that could potentially flood the mine must be captured and conveyed to Inverbrackie Creek.
(iv) Water quality considerations can be ignored for the purposes of this task.

Select the final location/layout/drainage scheme by developing a set of criteria including (but not limited to):
(i) Earthworks should be minimised
(ii) Stormwater should not cause significant damage, even in extreme events when the capacity of the stormwater system is exceeded (i.e. consideration of minor / major flow paths).

A number of alternatives should be considered and the final choice justified.

2. Design all pipes, including diameters, slopes and covers (the minimum pipe cover is 600mm). Note that there is no need to design the pits. Design flows for each pipe should be calculated using the deterministic rational method, although other methods might be more appropriate for calculating any design runoff from the bushland. Use a return period of 100 years. The design chart can be used to determine an appropriate pipe size, given a design slope and flow. Provide detailed calculations and justify the final design. All calculations should be checked by another group member; this should be clearly evident in your report.

3. Produce a full technical report, following the guidelines given in Sections 1,2 and 5,6 in ‘Guidelines for Coursework Submissions' on MyUni. This report will include
• A summary of outcomes related to Tasks 1-2, including calculations used for Task 2.
• A set of clear diagrams summarising your design.
The diagrams should include plans and longitudinal sections of the system showing ground level, pipe invert (bottom) and pipe obvert (top). Longitudinal sections should be drawn to appropriate (and possibly different) vertical and horizontal scales. The report should provide sufficient description of the procedure used to calculate the design flows. This can include clearly annotated and well described spreadsheet output and/or hand calculations on "Engineering Design Calculation" paper available to purchase from the Unishop. A 3 cm right-hand margin should be used to highlight important results.
The report should contain:
(i) Front cover or title page with title, names, etc.
(ii) Executive summary (including key background information and diagrams summarising the final design (layout and sizes))
(iii) Table of contents (including appendices, list of tables and list of figures, as well as their page numbers)
(iv) Introduction (starting on page 1 and including a site map)
(v) Main body (e.g. design methodology and approach, results etc.)
(vi) Summary of the final design (including diagrams of final layout and sizes)
(vii) Appendices, including detailed calculations and detailed diagrams of plan + longitudinal sections.

In addition:
(viii) All sections should be numbered (including the appendices)
(ix) All pages should be numbered sequentially (including pages in the appendices)
(x) All calculation pages should be dated (always include year eg. 21/9/2001), initialled by the person who performed the calculations and initialled by the checker
(xi) All assumptions you have made should be stated clearly
(xii) All source material must be referenced
(xiii) All Tables and Figures should be numbered, given a descriptive caption, and referred to in the text.

Attachment:- Engineering Hydrology.rar