2. Mangatawa catchment consents for earthworks, storm water ...
2. Mangatawa catchment consents for earthworks, storm water ...
2. Mangatawa catchment consents for earthworks, storm water ...
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These results include climate change, and there<strong>for</strong>e the “existing situation” presented reflects a<br />
lower per<strong>for</strong>mance than would occur under current climate conditions.<br />
The implication of Graph 1 is that the return period <strong>for</strong> a spill will improve from 33% to 13% AEP<br />
<strong>storm</strong> events.<br />
Graph 1 - Top Spill and Bruce Road peak discharges<br />
Top Spill and Bruce Rd - Peak Spill Discharge<br />
[Unmitigated and Mitigated]<br />
90.0<br />
80.0<br />
83.5<br />
Peak flow (m³/s)<br />
70.0<br />
60.0<br />
50.0<br />
40.0<br />
30.0<br />
20.0<br />
19.5<br />
43.8<br />
21.2<br />
56.4<br />
3<strong>2.</strong>4<br />
41.6<br />
10.0<br />
100%<br />
0.0<br />
0.0<br />
10%<br />
1%<br />
Annual Exceedence Probability (AEP)<br />
Mitigated Unmitigated Log. (Unmitigated) Log. (Mitigated)<br />
0%<br />
The volume of discharge across the highway is illustrated in the following graph <strong>for</strong> the mitigation<br />
option.<br />
Graph 2 - Top Spill and Bruce Road discharge volume<br />
Top Spill and Bruce Road - Spill Volume<br />
1,600,000<br />
[Unmitigated and Mitigated]<br />
1,400,000<br />
1,381,735<br />
Volume (m³)<br />
1,200,000<br />
1,000,000<br />
800,000<br />
600,000<br />
563,486<br />
771,933<br />
743,459<br />
400,000<br />
200,000<br />
179,730<br />
189,649<br />
337,339<br />
0<br />
100%<br />
0<br />
10%<br />
1%<br />
Annual Exceedence Probability (AEP)<br />
Mitigated Unmitigated Log. (Unmitigated) Log. (Mitigated)<br />
0%<br />
Beca // 17 March 2009 // Page 14<br />
3932036 // NZ1-1604459-15 0.15 Rev A
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