Embley

IRio Tinto AlcanEnvironmental Impact StatementSouth of Embley ProjectADCP current speed tails]02572 0.20-in a)a)e - O. 15C0.10U0.050.00 1 100:002007-04-2300:0004-2800:00 00:00 00:00 00:0005-03 05-08 05-13 05-18ADCP current direction [deg]2502- 200coI 1 iI)J 01 0 il II il 0 f I rili illW.2 isci-100-C-7 5G00:00 00:00 00:00 00:00 00:00 00:002007-04-23 04-28 05-03 05-08 05-13 05-18Figure 6-10Depth-averaged Measured Current Speed and Direction at Study Site6.1.4 WavesSmooth seas are frequently present at the Project site in the dry season (May to November).The westerly afternoon summer sea breezes are the only conditions favourable for generationof local seas.Other than local seas, wave events are generated by the following during the wet season:tropical cyclones, tracking some distance away, that propagate waves towards BoydPoint;tropical cyclones that track over the proposed SoE Port site. The largest waves areproduced if conditions are conducive to onshore winds; andmonsoon winds that occasionally blow over long fetches that may commence in theArafura Sea. Although these winds are not the same strength as cyclonic winds theystill generate very active sea conditions in the Weipa area.DERM has operated a long-term wave buoy site in Albatross Bay since 1978. Recorded summerdata from this site indicates that significant wave heights (Hsig) are below 1m for more than95% of the time. Hourly wave data statistics were also collected at the study site from August2006 to March 2008. During this time two notable wave events occurred, one associated withTropical Cyclone Nelson on 6 February 2007 and the other with ex-Tropical Cyclone He /en on 7January 2008. The highest significant wave heights at the site during Tropical Cyclone Nelsonwere 3.5m from the north-west, characterised by peak energy wave periods (Tn) of tenseconds.Section 6 Marine Page 6-10