Department of Defence
28-Jan-2014
DRAFT
Base Engineering
Assessment Program
Hydrologic and hydraulic
modelling report
116100196
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Date
28-Jan-2014
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Date
14-Mar-2012
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116100196
Table of Contents
1.0
2.0
3.0
4.0
5.0
Introduction
Previous Investigations
Hydrologic modelling
3.1
Runoff routing modelling
3.2
Results
Hydraulic modelling
4.1
Input data and modelling assumptions
4.1.1
Topography
4.1.2
One-dimensional elements (pipes and structures)
4.1.3
Roughness
4.1.4
Boundary Conditions
4.1.5
Modelling assumptions
4.2
Calibration/Validation
4.3
Results
Discussion
1
2
3
3
5
6
6
6
7
8
9
9
9
9
11
List of Figures
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Site location
Hydrologic model layout
Locations of hydrographs
Hydraulic model layout
Hydraulic model one-dimensional elements
Hydraulic model roughness grid
Hydraulic model boundaries
1% AEP flood event maximum flood depths
1% AEP flood event maximum flow velocities
10% AEP flood event maximum flood depths
10% AEP flood event maximum flow velocities
1
4
5
6
7
8
9
10
10
10
10
List of Tables
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Intensity Frequency Duration (IFD) data
Peak flows for various storm durations.
Site drainage details
Structure details
TUFLOW pipe model factors
Manning’s “n” roughness values
Hydraulic model boundaries
3
5
7
7
7
8
9
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1.0
Introduction
Brief intro to the site. Comment on the location, upstream catchment, site slopes, local drainage, historic flooding,
etc
Figure 1 shows the site location.
Figure 1
Site location
INSERT FIGURE
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2.0
Previous Investigations
List any previous hydrologic or hydraulic investigations.
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3.0
Hydrologic modelling
Hydrologic modelling was undertaken using two different techniques. A runoff routing model was used to
determine the external flows entering the site and rainfall on grid was used to represent rain falling on the study
area.
The following flood events were modelled:
-1% AEP
-10% AEP
-etc
3.1
Runoff routing modelling
Runoff routing modelling was undertaken utilising existing/new RAFTS/WBNM/RORB models created for ??
project. It included the following input data:
-Catchment delineation based on …..
-Fraction impervious based on ….
Table 1 shows the IFD data that was utilised for this model (EASTING and NORTHING coordinates). Please
note that this is based on the 1987 IFD data.
Table 1
Intensity Frequency Duration (IFD) data
Variable
Value
1 hour, 2 year ARI rainfall intensity
xx mm/hr
(1 I 2 )
12 hour, 2 year ARI rainfall intensity
(12I
2)
72 hour, 2 year ARI rainfall intensity
(72I
xx mm/hr
xx mm/hr
2)
1 hour, 50 year ARI rainfall intensity
xx mm/hr
(1I50)
12 hour, 50 year ARI rainfall intensity
(12I
50)
72 hour, 50 year ARI rainfall intensity
(72I
xx mm/hr
xx mm/hr
50)
F2
xx
F50
xx
Skewness (G)
xx
(ref: http://www.bom.gov.au/water/designRainfalls/ifd/index.shtml)
Figure 2 shows the hydrologic model layout.
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Figure 2
Hydrologic model layout
INSERT FIGURE SHOWING HYDROLOGIC MODEL LAYOUT
This model was calibrated to the following:
-Historic event
-Rational method calculation…
This modelling was based on the following assumptions:
-Fraction impervious values
-Initial loss = xx mm
-continuing or proportional loss = yy mm/hr or zz%
-storages
-routing
-other factors
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3.2
Results
Hydrographs were extracted from the hydrologic model at several locations. Figure 3 shows the location of these
hydrographs.
Figure 3
Locations of hydrographs
INSERT FIGURE SHOWING LOCATIONS WHERE HYDROGRAPHS WERE EXTRACTED
Table 2 shows the peak flows at these locations for various storm durations.
Table 2
Peak flows for various storm durations.
Location
15 min
storm
event
20 min
storm
event
25 min
storm
event
30 min
storm
event
45 min
storm
event
1 hour
storm
event
1.5
hour
storm
event
2 hour
storm
event
3 hour
storm
event
A
B
C
D
E
F
G
H
I
J
K
L
M
N
Based on the results in the above table, hydrographs for the xx duration storm event/s have been extracted from
the hydrologic model and used as inflow boundaries for the hydraulic modelling.
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4.0
Hydraulic modelling
Hydraulic modelling for this site was undertaken utilising TUFLOW software. This section describes the modelling
undertaken for this investigation. This model has the following components:
-Two-dimensional grid representing the ground surface elevations (topography)
-One-dimensional elements representing the underground pipes and structures
-Rainfall on grid
4.1
Input data and modelling assumptions
4.1.1
Topography
A two-dimensional grid was developed for the area shown in Figure 4. This figure also shows the ground surface
levels used in this modelling. These ground surface levels were based on the following data:
-LiDAR (reference)
-Additional ground survey?
-Any other info?
A x metre grid spacing was used for this model.
Figure 4
Hydraulic model layout
INSERT FIGURE SHOWING HYDRAULIC MODEL EXTENT AND GROUND ELEVATION.
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4.1.2
One-dimensional elements (pipes and structures)
Table 3 includes the details of the site drainage components. Some of these were modelled as one-dimensional
elements, others were represented in the two-dimensional grid. Figure 5 shows the location of the onedimensional elements.
Table 3
Site drainage details
Length/number
Comments
Open drains
Xx km
Modelled as 1D or 2D elements?
Underground pipes
Xx km ranging in size from x mm to
y mm diameter
Structures
Number of culvert/bridge structures
Table 4 shows details of the structures represented as one-dimensional elements.
Table 4
Structure details
Reference
Description
Configuration
Data source
A
Eg. Xx road crossing of yy drain
Size of culverts or
description of bridge
(eg single span),
Eg GIS data, site
inspection, previous
work
B
C
D
E
F
G
Table 5 shows the factors that should be used for the representation of pipes and culverts in TUFLOW.
Table 5
TUFLOW pipe model factors
Variable
Value
Entry loss
0.5
Exit loss
1.0
Height contraction coefficient
0.6
Width contraction coefficient
1.0 for RCP’s
0.9 for RCBC’s
Figure 5
Hydraulic model one-dimensional elements
INSERT FIGURE SHOWING PIPES AND STRUCTURE LOCATIONS
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4.1.3
Roughness
Table 6 shows the Manning’s ‘n’ roughness values that were adopted for this investigation.
Table 6
Manning’s “n” roughness values
Description
Manning’s ‘n’ value
Open space
X
Roads
X
Heavily vegetated areas
X
Buildings
X
Etc
X
Pipes and culverts
X
Figure 6 shows the roughness grid used for this modelling.
Figure 6
Hydraulic model roughness grid
INSERT FIGURE SHOWING ROUGHNESS GRID
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4.1.4
Boundary Conditions
Table 7 details the boundary conditions that were utilised for this investigation. Figure 7 shows the location of
these boundaries.
Table 7
Hydraulic model boundaries
Boundary location
Type
Details
Explain location (eg xx creek inflow)
QT
Hydrograph xy from RAFTS model
Explain location (eg xx creek inflow)
QT
Hydrograph xy from RAFTS model
Explain location (eg xx creek inflow)
QT
Hydrograph xy from RAFTS model
Downstream boundary (Creek
name)
HT or HQ
Values or reference
Rainfall on grid
Hyetographs to be developed based on IFD data in
Table 1.
Initial loss = xx mm
Continuing loss = yy mm/hr
Figure 7
Hydraulic model boundaries
INSERT FIGURE SHOWING LOCATION OF HYDRAULIC MODEL BOUNDARIES
4.1.5
Modelling assumptions
The following modelling assumptions were incorporated in this work:
-Time step
-Courant number
-Eddy viscosity
-Any other factors changed from default
-Etc.
4.2
Calibration/Validation
The hydraulic model was calibrated/validated against the following data:
-aaaaa
4.3
Results
The hydraulic model was run using the inputs and variables described in this report. The maximum water depths,
water surface elevations and maximum velocities were processed using TUFLOW –to-GIS and converted to
ASCII grids.
Figure 8 to Figure 11 show the modelled flood depths and velocities for the site for the 1% AEP and 10% AEP
flood events.
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Figure 8
1% AEP flood event maximum flood depths
INSERT FIGURE SHOWING LOCATION OF HYDRAULIC MODEL BOUNDARIES
Figure 9
1% AEP flood event maximum flow velocities
INSERT FIGURE SHOWING LOCATION OF HYDRAULIC MODEL BOUNDARIES
Figure 10
10% AEP flood event maximum flood depths
INSERT FIGURE SHOWING LOCATION OF HYDRAULIC MODEL BOUNDARIES
Figure 11
10% AEP flood event maximum flow velocities
INSERT FIGURE SHOWING LOCATION OF HYDRAULIC MODEL BOUNDARIES
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5.0
Discussion
Include discussion on:
-Model stability
-Reliability of results
-Areas flooded/not flooded
-Summary of flooding on site