Parameter
Stage 1
Stage 2
Unit
Breach slopes
0.6
0.6
H:1V
hr
Formation time
0.84
0.27
4.3
Outflow hydrographs
Outflow hydrographs were derived following standard breach routing equations by Fread [22] implemented in the software HEC-HMS version 4.12. Hydrograph estimations consider the unique stage-storage relationship of the outflow breach and breach parameters presented in Table 4.3. Table 4.4 summarises the resulting peak flows for each of the assessed scenarios. Derived breach hydrographs are provided in Figure 4.5 and Figure 4.6.
Table 4.4
Upper Mundic Gully TSF breach hydrographs
Peak outflow rate (m 3 /s)
Embankment
Stage 1
169
Stage 2
7,077
Project No PS213278 Upper Mundic Gully TSF Stage 1 and 2 DBA and CCA Mount Morgan Gold Mine Heritage Minerals
WSP JUly 2025 Page 17
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