2.3 Rainfall The Probable Maximum Precipitation (PMP) estimates were derived using guidelines from BOM considering the Generalised Short Duration Method (GSDM) and Revised Generalised Tropical Storm Method (GTSMR). The GSDM is applicable for catchments less than 1000 km 2 and critical durations smaller than 6 hours, whereas GTSMR applies based on geographical location of the catchment for storms with critical duration greater than 24 hours. Both approaches were explored to identify the critical duration of the PMP. The adopted PMP depths are presented in Table 3. Initial loss and continuing loss were kept at 0 mm and 1 mm/hr, respectively.
Table 3
Adopted PMP depths
Duration (hr)
Depth (mm)
Duration (hr)
Depth (mm)
0.25
220
9
1200
0.5
310
12
1280
0.75
390
15
1350
1
450
18
1410
1.5
580
24
1520
2
680
36
1720
2.5
750
48
1900
3
820
72
2220
4
940
96
2490
5
1040
120
2620
6
1090
The following sets of temporal patterns were applied in this study:
– The Average Variability Method (AVM) temporal pattern based on GSDM procedures for durations up to and less than 6 hours. – The 10 “Jordan” temporal patterns generated based on historical rainfall events for durations up to and less than 6 hours. – The Average Variability Method (AVM) temporal pattern based on GSTMR procedures for durations from and higher than 24 hours. – Both GSDM and GTSMR temporal patterns for all durations between 6 – 24 hours. For each duration, the PMF was adopted as the largest flood arising each of these temporal patterns. The critical duration was adopted as the one that resulted to the maximum flow between all the durations.
3.
Results
A range of durations were assessed to identify the critical inflow PMF storm, which are presented in Figure 2. It was found that the largest peak inflow of 323.6 m 3 /s resulted from a 15-minute storm. These six hydrographs were provided to Golder to assess the spillway design.
12624987 | Hydrological assessment of PMF for the Sandstone Gully Tailings Storage Facility 3
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