APPENDIX A SURVEYED STORMWATER PIPE NETWORK LOWER AUCKLAND CREEK CATCHMENT
10335-R01-AucklandCkFS-D.docx
A.1
SURVEYED STORMWATER PIPE INFORMATION
Surveyed stormwater pipe details in the lower Auckland Creek catchment are listed in Table A-1. A value of ‘-99999’ indicates the data is missing. Due to the number of pits, the details have not been tabulated. They have however been provided in dwg format as part of the electronic data handover. Blanks in the ‘Number of’ column mean there is only one pipe.
Table A-1 ID
Surveyed Stormwater Pipe Information Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
83a
C
0.71
1.96
1.89
0.375
84a
C
-99999
2.22
2.2
0.3
77a
C
12.72
10.75
10.26
0.5
78a
C
7.62
11.52
10.8
0.375
79a
C
11.48
11.83
11.57
0.375
80a
C
-99999
1.43
1.35
0.75
74a
C
21.8
3.47
2.71
0.5
75a
C
50.84
5.85
3.51
0.45
140a
C
12.47
6.63
5.93
0.5
76a
C
58.92
10.18
5.95
0.6
70a
C
12.11
2.71
2.36
0.5
71a
C
7.65
-99999
2.76
0.375
72a
C
0.537
3.56
3.53
0.375
73a
C
2.11
3.58
3.603
0.375
66a
C
2.77
4.3
3.72
0.375
67a
C
21.28
5.28
3.82
0.375
68a
C
13.46
3.72
3.15
0.375
69a
C
42.81
7.02
3.66
0.375
62a
C
30.65
1.2
0.99
0.6
63a
C
10.61
1.74
1.68
0.375
64a
C
21.99
1.87
1.72
0.375
65a
C
23.19
2.1
-99999
0.9
58a
C
0.63
1.68
1.64
0.45
59a
C
19.24
1.4
1.25
0.6
60a
C
19.21
1.21
1.21
0.6
61a
C
8.467
1.64
1.6
0.375
54a
C
41.73
2.88
1.77
0.375
55a
C
11.77
3.28
2.89
0.375
56a
C
21.11
1.56
1.45
0.3
57a
C
8
1.97
-99999
0.375
113a
C
1.281
2.75
2.74
0.375
114a
C
27.14
2.73
2.68
0.375
115a
C
2.83
2.63
-99999
0.45
116a
C
9.42
2.51
-99999
0.375
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
109a
C
22.38
2.53
2.31
0.45
110a
C
-99999
2.3
1.64
0.45
111a
C
50
1.55
-99999
0.45
112a
C
1.31
3.39
3.27
0.375
105a
C
17.8
1.94
1.87
0.4
106a
C
17.36
1.71
-99999
0.4
107a
C
16.56
2.08
2
0.4
108a
C
-99999
2.54
2.54
0.45
101a
C
6.39
2.76
2.68
0.35
102a
C
64.18
1.53
1.36
0.45
103a
C
20.35
2.35
2.15
0.3
104a
C
17.03
1.81
1.74
0.4
96a
C
0.383
1.88
1.8
0.575
98a
C
1.51
2.16
2.03
0.375
99a
C
1.07
2.13
1.75
0.375
100a
C
0.467
1.82
1.817
0.375
92a
C
11.94
2.17
2.15
0.375
93a
C
11.05
2.07
2.04
0.375
94a
C
0.43
2.11
2.09
0.375
95a
C
0.44
1.94
1.94
0.375
89a
C
10.26
1.96
1.24
1.05
91a
C
0.63
1.82
1.81
0.45
141a
C
13.35
2.15
2.13
0.375
85a
C
9.16
2.45
2.19
0.25
86a
C
9.28
1.84
1.83
0.45
87a
C
32.59
1.83
1.4
0.45
88a
C
5.04
2.39
2
0.375
129a
C
7.221
1.75
1.41
0.375
126a
C
-99999
-0.3
-0.45
1.9
3
128a
C
-99999
-0.83
-0.84
1.9
3
121a
C
1.49
2.38
2.31
0.45
122a
C
1.22
2.16
2.15
0.45
123a
C
28.7
2.02
0.8
1.2
124a
C
13.37
2.29
-99999
0.375
117a
C
0.76
2.5
2.5
0.45
118a
C
26.84
3.11
2.997
0.375
119a
C
52.97
2.98
2.46
0.375
120a
C
9.31
2.93
2.77
0.375
104931a
C
15.98
2.59
2.37
0.375
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
4
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
104930a
C
11.04
2.59
2.35
0.375
104848a
C
3.65
2.5
1.6
0.375
104853a
C
20.816
2.85
2.82
0.375
104860a
C
-999999
1.59
1.59
1.05
104861a
C
-99999
1.59
1.59
1.05
104933a
C
25.83
2.6
2.59
0.375
104932a
C
7.48
2.32
1.59
0.375
104849a
C
13.92
2.7
2.6
0.375
104950a
C
42.31
1.88
1.63
1.05
104946a
C
-99999
1.9
1.9
0.75
104934a
C
1.95
2.41
2
0.375
104941a
C
7.11
2.69
2.67
0.375
104945a
C
17.18
2.22
2.25
0.825
104855a
C
11.36
2.44
2.38
0.375
104951a
C
33.64
1.63
1.59
1.05
104948a
C
-99999
2.2
2.17
0.75
103978a
C
8.16
3.21
3.05
0.375
104949a
C
-99999
2.37
2.3
0.825
104944a
C
26.67
2.13
2.06
0.75
104937a
C
12.81
2.61
-99999
0.375
104936a
C
10.583
2.95
2.72
0.25
104852a
C
31.8
3.03
-99999
0.375
104935a
C
15.97
2.72
2.66
0.375
104859a
C
-99999
2.45
2.37
0.45
104939a
C
63.99
2.55
2.47
0.75
104938a
C
48.46
2.76
2.31
0.375
105397a
C
9.15
3.49
3.27
0.375
104857a
C
16.09
2.4
2.38
0.45
104870a
C
15.17
2.83
2.45
0.375
104947a
C
38.52
2.06
1.9
0.75
104858a
C
-99999
2.37
2.224
0.45
104867a
C
-99999
0.07
-0.3
1.9
3
102842a
C
-99999
-0.6
-0.83
1.9
3
104559a
C
44.77
1.21
0.89
1.05
104478a
C
1.56
2.24
2.14
0.45
102844a
C
25.8
3.53
3.53
0.2
102656a
C
70.12
2.531
-99999
0.9
104566a
C
25.83
0.54
0.5
1.2
3
104863a
C
79.75
0.45
0.26
1.2
3
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
1049.52a
C
35.7
1.27
-99999
0.45
105798a
C
-99999
1.5
1.5
0.65
105794a
C
5.81
2.37
-99999
0.375
102833a
C
35.203
3.48
1.5
0.45
105789a
C
1.21
1.76
1.758
0.375
105742a
C
18.86
2.66
2.54
0.35
105796a
C
1.49
1.31
1.31
0.45
105799a
C
-99999
1.55
1.55
0.65
105791a
C
3.84
2.11
1.73
0.375
105752a
C
-99999
1.65
1.65
0.65
105751a
C
-99999
1.69
1.69
0.65
105790a
C
1.48
2
-99999
0.375
105797a
C
-99999
1.73
1.69
0.65
105754a
C
27
1.72
1.73
0.65
105792a
C
3.99
2.08
1.77
0.375
105753a
C
-99999
1.73
-99999
0.6
105793a
C
16.53
2.22
2.04
0.375
105745a
C
68.62
1.69
1.59
0.45
105749a
C
40
1.72
1.72
0.65
105743a
C
15.52
2.02
1.97
0.375
104953a
C
69.71
1.57
0.1
1.05
105795a
C
28.25
1.88
1.69
0.45
105748a
C
50.21
2.2
1.73
0.65
105788a
C
27.2
2.52
2.32
0.375
20a
C
66.1
2.31
2.19
0.425
138a
C
20.103
1.41
1.16
0.75
139a
C
20.103
1.41
1.16
0.7
16a
C
22
2.4
2.07
0.45
18a
C
80.55
2.23
2.162
0.375
19a
C
15.64
2.4
2.36
0.375
12a
C
129.713
2.56
2.267
0.375
13a
C
14.07
2.489
2.04
0.25
14a
C
15.662
2.561
2.16
0.3
15a
C
12.023
2.079
1.997
0.3
8a
C
10.89
2.01
1.99
0.375
9a
C
61.38
2.19
2.003
0.375
10a
C
11.902
2.285
2.215
0.375
11a
C
88.334
2.487
2.1
0.375
136a
C
18.94
2.29
2.18
0.375
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
137a
C
18.312
2.34
2.1
0.375
6a
C
7.02
3.92
3.76
0.375
7a
C
0.44
3.79
3.77
0.4
134a
C
11.74
2
1.8
0.3
135a
C
11.66
2.17
2.11
0.375
2a
C
102.538
2.361
1.89
0.375
4a
C
101.9
-99999
1.65
0.525
104481a
C
14.53
2.09
1.58
0.65
104479a
C
1.134
2.33
2.31
0.45
104480a
C
13.06
2.28
2.18
0.525
50a
C
0.858
1.93
1.85
0.35
51a
C
0.585
1.98
1.89
0.375
52a
C
12.19
1.67
1.57
0.45
53a
C
14.78
1.43
1.43
0.75
46a
C
33.72
2.104
1.978
0.3
48a
C
-99999
2.29
2.01
0.45
49a
C
12.06
0.59
0.41
0.375
43a
C
67.719
2.27
1.702
0.375
44a
C
11.605
1.958
1.89
0.45
38a
C
0.342
2.002
1.995
0.3
34a
C
0.442
2.152
2.152
0.4
36a
C
19.597
1.836
1.739
0.6
37a
C
52.313
1.97
1.853
0.6
30a
C
39.72
2.462
2.242
0.375
26a
C
39.473
1.6
1.29
0.75
27a
C
40.381
2.081
1.936
0.375
28a
C
37.64
1.92
1.74
0.525
22a
C
24.68
1.84
1.69
0.375
23a
C
13.7
1.943
1.84
0.375
24a
C
23.21
1.9
1.817
0.375
104012a
C
49.585
1.883
1.694
0.375
104096a
C
12.48
2.138
2.062
0.375
104097a
C
15.7862
2.236
2.139
0.375
104004a
C
12.31
2.1
1.95
0.375
104015a
C
9.11682
1.45
1.25
0.525
104101a
C
69.249
1.81
1.768
0.375
104021a
C
22.693
1.65
1.65
0.65
104018a
C
24.64461
1.763
1.65
0.525
103005a
C
27.79101
1.8
1.45
0.525
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
104014a
C
20.37922
1.82
1.81
0.45
103002a
C
13.8541
1.84
1.82
0.375
103004a
C
17.35664
1.9
1.85
0.375
102756a
C
98.07
1.94
1.74
0.525
100400a
C
3.96
1.5
1.43
0.75
100390a
C
23.99
2.48
2.35
0.25
100313a
C
70.11
1.32
0.71
0.75
102754a
C
118.7
2.45
1.715
0.75
100399a
C
94.08
1.41
1.134
0.75
101128a
C
10.06
1.63
1.4
0.75
101129a
C
11.95
1.73
1.66
0.75
102347a
C
12.66
1.71
1.7
0.525
100397a
C
11.81
1.7
1.7
0.525
101130a
C
11.96
1.7
1.71
0.75
101127a
C
19.69
1.66
1.51
0.75
101295a
C
72.36
1.4
0.87
0.675
100398a
C
119.72
1.68
1.47
0.75
100392a
C
11.7
2.08
2
0.375
100391a
C
26.81
1.98
1.9
0.375
100469a
C
19.08318
2.36
2.3
0.45
100471a
C
44.1589
2
0.25
0.45
101293a
C
61.86
3.71
1.72
0.375
103741a
C
55.66
2.33
1.7
0.3
104774a
C
14.8405
3.425
2.95
0.375
102596a
C
31.67
1.34
0.87
0.45
103466a
C
9.332
1.45
1.4
0.45
103465a
C
13.194
1.59
1.56
0.45
130a
C
14.84053
2.9
2.2
0.375
131a
C
13.95646
2.95
2.25
0.375
101161a
C
5.21138
3.42
2.95
0.375
103771a
C
32.76604
2.14
0.67
0.6
104649a
C
91.219
1.52
1.31
0.45
104643a
C
58.131
1.89
1.53
0.3
104646a
C
42.215
1.67
1.65
0.375
104647a
C
13.863
1.63
1.525
0.375
104644a
C
25.079
1.91
1.84
0.375
104648a
C
95.29
1.782
1.1
0.525
104650a
C
6.419
1.845
1.82
0.375
104645a
C
12.118
1.74
1.72
0.3
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
105236a
C
20.226
1.95
-99999
0.45
105235a
C
17.69
1.91
1.74
0.45
105233a
C
15.83
1.75
1.742
0.375
105238a
C
60.568
1.71
1.68
0.45
101926a
C
70.42
2.14
2.041
0.375
105239a
C
5.25
2
1.92
0.45
105234a
C
60.89
1.68
1.43
0.6
105237a
C
60.89
1.68
1.43
0.45
100393a
C
35.99
2.04
2.01
0.375
100230a
C
12.215
2.14
2.09
0.45
100228a
C
16.455
2.16
2.14
0.275
100394a
C
14.396
2
1.95
0.45
100396a
C
122.793
1.89
1.48
0.6
100229a
C
23.795
2.22
2.14
0.275
100231a
C
38.669
2.32
2.14
0.45
100232a
C
66.423
2.08
1.9
0.6
103283a
C
8.78
-99999
1.78
0.45
150a
C
14.503
1.5
1.45
0.6
103769a
C
21.838
1.6
1.5
0.45
103288a
C
14.404
1.52
1.5
0.6
103854a
C
73.513
1.93
1.61
0.45
101925a
C
61.527
2.116
-99999
0.45
103287a
C
70.644
1.7
1.56
0.6
103281a
C
12.596
2.04
1.786
0.375
103464a
C
0.834
103551a
C
65.35
2.178
1.86
0.45
103286a
C
26.148
1.77
1.73
0.6
102171a
C
3.18
0.51
0.45
0.9
102172a
C
3.182
-99999
1.95
0.9
102708b
C
70.03
1.91
0.51
0.9
103549a
C
85.41
2.94
2.22
0.3
103460a
C
12.52
1.87
1.707
0.375
103548a
C
8.39
2.81
2.68
0.275
104642a
C
10.84
2.68
2.41
0.275
102708a
C
30.38
1.9
0.51
0.35
103469a
C
11.7
1.08
0.88
0.6
102634a
C
11.32
1.71
1.53
0.375
103561a
C
48.529
2.79
1.97
0.375
102638a
C
78.6
1.45
0.59
0.375
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
2
2
0.45
2
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
101093a
C
16.31
1.72
1.61
0.375
101092a
C
6.52
1.83
1.75
0.375
101018a
C
7.063
1.54
1.46
0.375
101091a
C
8.35
2.09
1.8
0.375
103455a
C
5.06
-99999
1.68
0.375
103472a
C
60.84
-99999
0.36
0.75
103470a
C
22.304
1.33
1.12
0.6
103471a
C
20.592
0.86
-99999
0.75
101335a
C
36.74
1.45
1.37
0.675
101415a
C
12
2.08
1.89
0.375
102751a
C
25.23
1.86
1.84
0.45
102838a
C
8.77
1.32
0.84
0.75
101334a
C
78.86
1.68
1.44
0.575
101329a
C
12.24
2.12
1.94
0.375
102828a
C
3.12
2.53
2.4
0.375
102753a
C
55.64
1.81
-99999
0.45
103632a
C
7.706
2.674
2.654
0.3
101333a
C
75.91
2.06
1.71
0.525
101331a
C
28.04
-99999
2.09
0.525
101330a
C
27.26
2.24
-99999
0.375
103721a
C
32.77
2.638
2.457
0.3
103635a
C
16.608
2.08
1.695
0.375
103452a
C
41.796
2.817
2.715
0.3
103722a
C
8.568
2.658
2.64
0.3
103863a
C
14.37
1.73
1.38
0.375
103862a
C
21.314
1.58
1.42
0.375
104851a
C
16.14
1.74
1.712
0.375
103634a
C
39.575
2.462
2.183
0.375
102633a
C
9.42
1.82
1.74
0.375
104850a
C
27
1.68
1.55
0.375
2
103778a
C
59.1
1.31
0.92
0.375
3
103633a
C
24
1.6
1.4
0.375
2
103853a
C
11.854
2.029
1.974
0.375
103552a
C
87.47
1.37
-0.65
0.9
102631a
C
11.427
1.88
1.79
0.375
102653a
C
5.765
1.35
1.3
0.75
103851a
C
12.032
1.77
1.614
0.3
103768a
C
44.264
1.9
1.598
0.45
103770a
C
7.731
1.591
1.45
0.525
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
2
ID
Type
Length (m)
US IL (mAHD)
DS IL (mAHD)
Width/Diameter (m)
103852a
C
12.03
2.02
1.847
0.3
81a
C
0.68
1.6
1.48
0.375
82a
C
0.58
1.64
1.59
0.375
90a
R
25.5
2.98
2.72
0.6
0.3
125a
R
185.6
0.27
0.07
1.2
3
127a
R
-99999
-0.45
-0.59
1.9
3
21a
R
3.505
2.73
-99999
0.45
0.225
2
17a
R
11
2.5
2.45
0.45
0.225
2
132a
R
4.12
2.61
2.49
0.45
0.23
2
133a
R
3.75
2.53
2.5
0.45
0.25
2
3a
R
12
1.79
1.59
0.45
0.225
2
5a
R
11.74
1.63
1.47
0.45
0.225
2
1a
R
23.24
1.948
1.878
0.45
0.225
47a
R
10.953
1.45
1.4
1.25
0.75
42a
R
0.46
1.906
1.9
0.45
0.225
45a
R
16.631
1.86
1.73
0.45
2
39a
R
0.476
2.07
2.05
0.45
0.225
40a
R
0.627
1.941
1.94
0.45
0.225
41a
R
0.441
1.62
1.61
0.45
0.225
35a
R
0.447
2.317
-99999
0.3
0.25
31a
R
0.471
2.146
2.139
0.45
0.225
32a
R
0.583
2.09
2.09
0.45
0.225
33a
R
0.591
1.707
1.694
0.425
0.225
29a
R
0.545
1.77
1.72
0.425
0.225
25a
R
4.54
2.64
2.63
0.45
0.225
103462a
R
26.59
2.56
2.18
0.6
0.3
10335-R01-AucklandCkFS-D.docx
Height (m)
Number of
2
A.2
SURVEY DRAWINGS
10335-R01-AucklandCkFS-D.docx
APPENDIX B TEMPORAL PATTERN SELECTION
10335-R01-AucklandCkFS-D.docx
B.1
MEMORANDUM - ANALYSIS OF RAINFALL IN EAST COAST NORTH REGION
10335-R01-AucklandCkFS-D.docx
Water Modelling Solutions Pty Ltd A | Level 13, 269 Wickham Street Fortitude Valley QLD 4006 Australia
P | 07 3252 7448 E | admin@watermodelling.com.au W | www.watermodelling.com.au
GPO Box 664 Brisbane QLD 4001
ACN | 158 809 593 ABN | 75 158 809 593
MEMORANDUM To
Nikeeta Roche
From
Eoghain O’Hanlon
Copy
Celisa Faulkner
Reference
10335-M01-A
Date
7 May 2019
Pages
9
Subject
Analysis of Rainfall in East Coast North Queensland Region
Dear Nikeeta, One of the key objectives of the Auckland Creek Flood Study is to update the existing hydrological and hydraulic modelling in accordance with the new ARR 2016 data and guidelines. The new guidance of ARR 2016 recommends examining an ensemble of temporal patterns that have been developed for different regions for each duration of an AEP design storm event. ARR 2016 notes that it is not practical to run all ten temporal patterns that have been provided for each duration in hydraulic modelling. However, it is recommended to “run a separate hydrological modelling process of the whole catchment of interest in order to determine the average pattern in terms of peak flow or volume depending on the problem” and that “testing has demonstrated that on most catchments large number of events in the ensemble patterns are clustered around the mean and median” (ARR 2016, Book 2, Section 5.9.2). In order to achieve a balance between model run times and the guidance of ARR 2016 to use an ensemble of temporal patterns, WMS put forward in its proposal to use three temporal patterns for each chosen critical duration. Initially, all ten temporal patterns for a range of storm durations were run in the hydrologic model to determine the critical durations for different regions of the catchment. The hydrological output for the median temporal pattern for each duration was modelled hydraulically in order to make a preliminary assessment as to which durations were critical throughout the catchment and would be adopted for the design event runs. In undertaking this initial assessment, it was discovered that the results indicated the critical durations throughout the Auckland Creek catchment were not reasonable in that the overall critical duration for multiple regions in the catchment was the 12-hour duration. This was also the case for the upper sub-catchments. Given these unexpected results the objectives of this memorandum are as follows: •
To present the results from the initial hydraulic model and to explain why they are problematic;
•
To present the analysis that WMS undertook of the temporal rainfall patterns for the East Coast North Queensland Region in which Auckland Creek is located in order to discover why these results occurred; and
•
To suggest, subject to approval, some ways to proceed forward in light of the analysis undertaken.
1 INITIAL RESULTS In a catchment the size of Auckland Creek (56 km2) it is expected that the length of the critical storm will vary from shorter to longer durations when moving from upstream to downstream. The previous study undertaken by Engeny based on ARR 1987 guidelines adopted the 1-hour, 2-hour, 3-hour, 4.5-hour and 6-hour events as the critical storms for the catchment. In undertaking a critical duration analysis based upon the data derived from ARR 2016 and using the median storm for each duration from the ensemble of temporal patterns, WMS found the output from both the hydrologic and the hydraulic models to present results for the critical durations that were not acceptable to sound engineering judgement. The output of the hydraulic model consists of a flood envelope that is derived from combining the results from the ensemble of storm durations that were run in the hydraulic model. This flood envelope indicates which storm durations contributed the maximum water level at any given location within the flood extent to determine which storm durations are critical within the catchment. For the Auckland Creek catchment ten storm event durations were examined ranging from 0.5 hours to 18 hours.
10335-M01-CriticalDurations-A.docx
Page 1
In assessing the critical flood envelope of the Auckland Creek catchment, it was noted that the 12-hour duration storm event was critical throughout nearly the entire extent of both the hydrologic and the hydraulic models. The critical duration map for the 1% AEP event is shown in Figure 1-1. It is evident the 12-hour storm duration is critical even in the upstream areas of the main flow path as well as contributing tributaries in which it would be expected that a shorter duration storm such as a 1-hour or 2-hour storm event would be critical. Another flood envelope was created using the same modelling results but leaving out the 12-hour duration storm event. This result revealed that, though not as dominant as the 12-hour duration storm, the 9-hour storm event became critical throughout much of the catchment though not to the same extent as the 12-hour duration storm event. As shown in Figure 1-2, there is a better representation of some of the expected shorter durations such as 45 minutes and 2 hours in the catchment tributaries but still very little variation throughout the main flow path from upstream to downstream is observed. The 4.5-hour duration is the critical event in a short section of the channel towards the outlet upstream of the Mariner. Further analysis was performed in which the flood envelope excluded both the 12-hour and 9-hour duration storm events, see Figure 1-3. The results show the 4.5-hour duration storm as critical throughout the main flow path which is within an acceptable critical response range for a catchment of this size. There is a better representation of the transition of the critical storm from shorter to longer durations in the tributaries. However, it was noted that in the main channel the 6-hour duration storm was critical further upstream than the 4.5-hour duration storm. The expected transition would be for the 6-hour duration storm to be critical downstream of the 4.5-hour storm duration.
10335-M01-CriticalDurations-A.docx
Page 2
Figure 1-1
Critical Durations for Auckland Creek Catchment – 1% AEP Event
10335-M01-CriticalDurations-A.docx
Page 3
Figure 1-2
Critical Durations for Auckland Creek Catchment Disregarding the 12-Hour Storm – 1% AEP Event
10335-M01-CriticalDurations-A.docx
Page 4
Figure 1-3
Critical Durations for Auckland Creek Catchment Disregarding 12-Hour and 9-Hour Storm Events – 1% AEP Event
10335-M01-CriticalDurations-A.docx
Page 5
2 ANALYSIS OF TEMPORAL PATTERNS In order to better understand these unusual outputs from the hydraulic model, WMS undertook a more in-depth analysis of the hydrological inputs. All the temporal patterns for the East Coast North Queensland region for the 6-hour, 9-hour, 12-hour, 18-hour and 24-hour duration storm events were analysed. This analysis included examining the rainfall hyetographs of the various temporal patterns, examining the Annual Exceedance Probability (AEP) of shorter rainfall bursts within these longer duration events, and examining the impact of the application of Areal Reduction Factors (ARFs). The findings examined in this section are applicable in varying degrees to all of the durations analysed (6 to 24 hours). In the interests of simplicity results from the 12-hour storm event which was particularly dominant will be presented in this memorandum as illustrative of the problems that were discovered. The rainfall hyetograph of the temporal pattern of the median storm for the 12-hour 1% AEP storm is shown in Figure 2-1. This figure indicates a significant percentage of the total rainfall falling within the first two hours of this storm event.
50 45 40
Rainfall (mm)
35 30 25 20 15 10 5 0
Time (hrs) Figure 2-1
Hyetograph of the Median Temporal Pattern for the 12 hr Storm Event
An analysis was undertaken of this rainfall pattern to determine the AEP for shorter bursts of rainfall within the storm event from 0.5 hours up to 12 hours and plotting the AEPs derived against the IFD values for the BOM rainfall in this area. This analysis provides a way of assessing the intense shorter embedded bursts within this temporal pattern compared to the intensity that would be expected of a shorter duration event for the same AEP. The result of this AEP analysis is shown in Figure 2-2 for the median temporal pattern for the 12-hour duration storm.
10335-M01-CriticalDurations-A.docx
Page 6
1000
Total Rainfall Event Depth (mm)
63.2% AEP 50% AEP 20% AEP 10% AEP 5% AEP 100 2% AEP 1% AEP Median Storm
10 0.50
Figure 2-2
Duration (hrs)
5.00
Hyetograph of the Median Temporal Pattern for the 12-Hour Storm Event
Figure 2-2 shows that the median temporal pattern for the 12-hour storm event in the Auckland Creek catchment is generally tracking just above a 1% AEP for durations much shorter than 12 hours. This temporal pattern therefore has embedded bursts that are more intense than what would be expected for shorter duration events of the same AEP. These embedded storms of shorter duration within the median 12-hour temporal pattern explain why the 12-hour duration storm appears to be critical, in areas of the catchment in which a shorter duration storm event would be expected to be critical. An additional aspect that exacerbates this effect of giving undue weight to longer duration storms is that the areal reduction factors (ARFs) that are applied to the BOM design rainfalls. ARFs are intended to account for the fact that a rainfall event will not be as intense over larger catchment areas especially for very short and therefore very intense duration events. The ARFs that have been applied to the BOM rainfall for the 1% AEP are shown in Table 2-1.
Table 2-1
Adopted ARF Factors for Auckland Creek for the 1% AEP Event
Storm Duration
0.5 hr
1 hr
1.5 hr
2 hr
3 hr
4.5 hr
6 hr
9 hr
12 hr
18 hr
24 hr
ARF
0.77
0.81
0.82
0.83
0.84
0.87
0.90
0.92
0.93
0.94
0.95
Table 2-1 shows rainfall for shorter duration events is reduced by a larger factor than longer duration events such as the 12-hour duration storm event. This difference in reduction factors will further increase internal rainfall bursts the AEP of 12-hour duration storms temporal patterns when compared to shorter duration storm events. This effect is shown in Figure 2-3 which plots the same storm as shown in Figure 2-2 but against the BOM IFD rainfall with ARFs applied.
10335-M01-CriticalDurations-A.docx
Page 7
1000
Total Rainfall Event Depth (mm)
63.2% AEP 50% AEP 20% AEP 10% AEP
100
5% AEP 2% AEP 1% AEP Median Storm
10 0.50 Figure 2-3
Duration (hrs)
5.00
Hyetograph of the Median Temporal Pattern for the 12-Hour Storm Event with Areal Reduction Factors Applied
Because larger ARFs are applied to shorter duration rainfall, the 12-hour duration storm median temporal pattern internal bursts are clearly greater than the 1% AEP line for all durations up to approximately 9 hours before becoming a 1% AEP storm at approximately 12 hours as would be expected since it is the temporal pattern for a 1% AEP 12-hour storm event. Prior to the application of ARFs to the design rainfall as in Figure 2-2, the 12-hour storm was tracking only slightly above or just on the 1% AEP line for durations shorter than 12 hours.
3 SUGGESTED SOLUTION As all the temporal patterns have been examined and subjected to an IFD analysis all of the problematic temporal patterns have been identified. The median storm, as the above analysis indicates, is one of these problematic storms. In the case of the 12-hour duration 1% AEP storm, four of the ten temporal patterns were tracking significantly above a 1% AEP event for shorter durations when plotted against the aerially reduced BOM rainfall. There are, however, a number of temporal patterns that are indicative of a more realistic pattern of rainfall for such a duration. Figure 3-1 shows an example where the AEP of shorter duration rainfall bursts for this 12-hour duration temporal pattern approximates a 10% AEP for durations up to 2 hours and steadily rises through 5% and 2% AEP events until it approximates a 1% AEP for 12 hours as would be expected. It is suggested that in selecting the temporal patterns to run for design events for durations of 6 hours and longer that the temporal patterns that contain short duration bursts embedded within the temporal pattern be excluded, even if that is the median storm. Instead, WMS will select a range of temporal patterns from those that do not include bursts that are more intense than what would be expected of shorter duration storms for the same AEP.
10335-M01-CriticalDurations-A.docx
Page 8
1000
Total Rainfall Event Depth (mm)
63.2% AEP 50% AEP 20% AEP 10% AEP 100
5% AEP 2% AEP 1% AEP Temporal Pattern
10 0.50
5.00 Duration (hrs)
Figure 3-1
Hyetograph of a Selected Temporal Pattern for the 12-Hour Duration Storm Event without Short Intense Embedded Rainfall Bursts
4 SUMMARY A summary is provided below. 1.
The hydraulic modelling indicated that storm durations significantly longer than those previously adopted in the Auckland Creek Flood Study were critical for the catchment. Furthermore, these longer durations were critical throughout the vast extent of the catchment including locations in the far upstream sections where much shorter durations would be expected to be critical.
2.
An analysis of the temporal patterns for storm durations ranging from 6 hours to 24 hours for the 1% AEP for the East Coast North Queensland region revealed that there was a problem with embedded bursts within some of the temporal patterns for these storm durations that had a higher intensity of rainfall than shorter events of the same AEP. The problem included the temporal pattern for the median storm. The impact of areal reduction factors which are greater for shorter events was observed to further exacerbate the problem.
3.
It is suggested that these temporal patterns be excluded from the analysis even if they include the median storm. WMS will use engineering judgement to make a selection of temporal patterns for these durations from the remaining temporal patterns that yield a more realistic result for these durations.
We request that Council provide a written agreement on the proposed methodology to progress the study prior to WMS progressing the design event modelling. Please do not hesitate to contact me if you require further clarification.
Yours sincerely,
Eoghain O’Hanlon Principal Scientist Team Lead
10335-M01-CriticalDurations-A.docx
Page 9
B.2
TEMPORAL PATTERN SELECTION
The analysis was undertaken for all AEP events for durations ranging from 3 to 18 hours. The following design storms utilised the same temporal patterns: •
63.2% AEP, 39% AEP and 20% AEP events;
•
10% AEP and 5% AEP events; and
•
2% AEP, 1% AEP, 0.5% AEP and 0.2% AEP events.
To allow for different rainfall intensities, each AEP event was adjusted with a net depth (mm) factor taken from ARR 2016 Data Hub for the East Coast North Region. As an example, the following graphs in Section B.2.1 show the temporal pattern rainfall for the 1% AEP event and 9-hour storm duration for each of the ten temporal patterns versus the IFD rainfall. These graphs were used as the basis for excluding and selecting which temporal patterns would be used for the hydraulic model runs. As per the summary provided in Appendix B.1, temporal patterns for the above durations which displayed higher intensities/rainfalls than those of a shorter duration for the same AEP event were excluded from the ten temporal patterns and a new median temporal pattern was selected. Spreadsheets with plots equivalent to those in Section B.2.1 but for the remaining modelled storm durations for the 1% AEP event are provided as part of the electronic data handover for the project.
10335-R01-AucklandCkFS-D.docx
B.2.1
1% AEP 9 Hour Temporal Pattern Analysis
Figure B-1
9-Hour Storm Duration - Temporal Pattern One
Figure B-2
9-Hour Storm Duration - Temporal Pattern Two
10335-R01-AucklandCkFS-D.docx
Figure B-3
9-Hour Storm Duration - Temporal Pattern Three
Figure B-4
9-Hour Storm Duration - Temporal Pattern Four
10335-R01-AucklandCkFS-D.docx
Figure B-5
9-Hour Storm Duration - Temporal Pattern Five
Figure B-6
9-Hour Storm Duration - Temporal Pattern Six
10335-R01-AucklandCkFS-D.docx
Figure B-7
9-Hour Storm Duration - Temporal Pattern Seven
Figure B-8
9-Hour Storm Duration - Temporal Pattern Eight
10335-R01-AucklandCkFS-D.docx
Figure B-9
9-Hour Storm Duration - Temporal Pattern Nine
Figure B-10
9-Hour Storm Duration - Temporal Pattern Ten
10335-R01-AucklandCkFS-D.docx
B.2.2
Excluded and Selected Temporal Patterns for the 2% AEP to 0.2% AEP Events
Based on the analysis undertaken with a subset of data shown in the graphs in Section B.2.1, the following temporal patterns were excluded for the 2% AEP, 1% AEP, 0.5% AEP and 0.2% AEP events. With the remaining suitable temporal patterns, a new temporal pattern was selected based on what the median was of the remaining patterns. Temporal patterns which were excluded based on the above graphs are highlighted in red in Figure B-11. The newly adopted temporal pattern is highlighted in green, calculated based on the median of the remaining temporal patterns.
Figure B-11
Temporal Pattern Selection
10335-R01-AucklandCkFS-D.docx
APPENDIX C CALIBRATION MAPPING
10335-R01-AucklandCkFS-D.docx
APPENDIX D DESIGN STORM MAPPING
10335-R01-AucklandCkFS-D.docx
APPENDIX E CLIMATE CHANGE MAPPING
10335-R01-AucklandCkFS-D.docx
APPENDIX F TIDAL MAPPING
10335-R01-AucklandCkFS-D.docx
APPENDIX G PMP EVENT MAPPING
10335-R01-AucklandCkFS-D.docx
APPENDIX H SENSITIVITY ANALYSIS MAPPING
10335-R01-AucklandCkFS-D.docx