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Rio Tinto AlcanEnvironmental Impact StatementSouth of <strong>Embley</strong> ProjectGulf model predictionImiWeipa storm surge gauge (MSQ) - observed (mj -,Weipa storm surge gauge (IvISCI) - predicted [m] '30.5Ai0' Aii' AiGtty -0.507-1.500:00 00:00 00:00 00:00 00:00 00:00 00:002007-05-22 05-24 05-26 05-28 05-30 06-01 06-03Figure 6-5Outer Model Water Level Prediction Compared with Weipa Storm TideGaugeGulf model predictionWeipa No 2 Beacon observed [m]0.5Co2-15-00:00 00:00 00:002003-07-28 08-02 08-0T00:0008-12Figure 6-6Observed Water Levels at Beacon 2 Compared with Gulf ModelPredictionVerification of the Inner model was achieved by comparing water level, and current speed anddirection against measurements from the ADCP deployed at the Boyd Point site. Goodagreement between measured and modelled hydrodynamics in the study area was found (referFigure 6-7).The Inner hydrodynamic finite-volume model (flexible mesh) was used in plume modelling andto quantify current speed and direction information to assess the potential impacts of turbidity,siltation, and sediment mobilisation as a result of dredging and disposal.Section 6 Marine Page 6-6
Rio Tinto AlcanEnvironmental Impact StatementSouth of <strong>Embley</strong> ProjectADCP water level [m]Inner model water level [rn]E0.5co 0.0-1 509:00 00:00 00:00 00:00 00:00 00:002007-05-08 05-10 05-12 05-14 05-16 05-180.25ADCP current speed Irnis1Inner model current speed [Ws]0.200.15V, 0.100.0500:002007-05-0800:0005-1000:0005-1200:0005-1400:0005-1500:0095-18I I IADCP current direclion [deg]Inner model current direction [deg]200150-100I5009:00 00:00 00:00 00.00 00'002007-05-10 05-12 05-14 05- 6 05-18Figure 6-7Measured (ADCP) Data Compared with Inner Model PredictionPredicted peak flood (incoming) and ebb (outgoing) tide current vectors at the proposed portsite are presented in Figure 6-8 and Figure 6-9. Current vectors over the tide cycle indicateflow from the north-east or south-west depending on the tidal phase. Peak model currents areapproximately 0.3m/s. ADCP measurements demonstrate the current speed is relatively uniformover depth.The existing wave climate within the area is described in Section 6.1.4 and the estimate ofannual longshore sediment transport is reported on in Section 6.1.5.The coastline between Boyd Point and Pera Head is relatively straight and has a bearing of 2100with respect to true north (i.e. 210°N). Above the water line the beach is relatively wide andcontains a substantial volume of sand material. Nearshore beach slope immediately above andbelow the water line is steep inferring a reflective beach type (i.e. convex profile that reflectslow wave energy).Under existing coastal conditions, the shoreline either side of the proposed port developmentarea appears to be uniform, inferring a balance of sediment supply in and out of thecompartment.Section 6 Marine Page 6-7
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