EagFirRsp

The pre- and post-development overland flow rates are summarised in Table 5 below, where they are seen to
be greatly reduced as a result of the development.

Nett Result: No adverse impact; substantial benefits

Table 5: Overland Flows Through The Tait Street Properties, Nodes N45 to N50
 Event                Pre-Development       Post-Development
 AEP (ARI)            (m3/s)                (m3/s)
 AEP 1% (100 yr)      1.02                  0.36
 AEP 2% (50 yr)       0.88                  0.32
 AEP 5% (20 yr)       0.80                  0.30
 AEP 10% (10 yr)      0.67                  0.26
 AEP 20% (5 yr)       0.62                  0.22
 AEP 50% (2 yr)       0.37                  0.13
 AEP 67% (1yr)        0.29                  0.09


Water Levels In Tait Street At Node 45, At The Point of Inflow For Roofwater From New Lots 1 to 9.

The piping of roofwater from the new lots 1 to 9 will provide an initial surge of runoff to Tait Street.
However, the initial surge will be completely offset by the greatly reduced catchment area further upslope,
such that the water levels in Tait Street will be significantly reduced, as in Table 6 below.

Nett Result: Substantial benefits; no significant adverse impact; no mitigation required.

Table 6: Water Levels In The Tait Street Kerb/Channel At Node N45
 Event                Pre-Development        Post Development
 AEP (ARI)             EL (m)                 EL (m)
 AEP 1% (100 yr)       3.67                   3.63
 AEP 2% (50 yr)        3.66                   3.62
 AEP 5% (20 yr)        3.66                   3.61
 AEP 10% (10 yr)       3.65                   3.60
 AEP 20% (5 yr)        3.62                   3.59
 AEP 50% (2 yr)        3.59                   3.58
 AEP 67% (1yr)         3.58                   3.57


Water Levels At Node N14B At The Sag In Tait Street.

Node 14B is located in the kerb/channel at the Tait Street sag. The pre-and post-development water levels in
the sag are summarised in Table 7, on the following page.

In the absence of any mitigation, the increased imperviousness of the development site would adversely affect
the water levels in the Tait Street sag, across the full range of AEP, and this would be further affected (either
way) by the relative changes in hydrograph timing.

With the basin in place, the impacts in the 1 to 2 year events are limited to an afflux of 0.01 metre, and the



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