Ezybouy said..
Some good information. I spent some time looking at the landgate photos on line with a focus on where the sand was moving from an where to. It was quite obvious that the sand was moving along from Mersey Point. Did Sam mention how much sand the council dumped at Mersey Point? Did Sam mention anything about Friends of Shoalwater adding shell grit to the sand bar (prior to it being named Tern Island) all of this in the time frame mentioned in the developing of Tern Island. I think we al new the drains have been there prior to tern island but that was at a time when currents flushec the area. So i am interested in his response to what is causing the algae other than nutrients. Really getting down to 2 options maintain it for public use iir fill it in. Should be an interesting meeting.
hi Ezybouy
there has been some data collected and studies done indicating that the majority of sand over at secret harbour that is pushed north in prevailing summer conditions (and not just trapped at the ever widening point) actually goes ofshore along the reef line, and then travels back in shore once past the warnbro basin by a couple of feeds, most notably:
- penguin island to mersey point
- the sand bar shown in transformative phase on the aerial photos slightly to the south (which would now be a fully submerged feed, but could change (increase / decrease) depending on sand and oceanoggraphic conditions in a given season)
similar process happens in cockburn sound, with the feed coming onto the shore near Catherine Point groyne.
there are some documents around sediment cells in WA, but might not have the level of detail you want for this location eg:
www.transport.wa.gov.au/mediaFiles/marine/MAC-P-SedimentCellsWA.pdfPeruse some of the references for specific studies on Mersey Point and Warnbro Sound if you want more detail on the sand transport pathways - there is just a bit more to it than "the sand is coming from Mersey Point", though that is certainly a component based on the info available. Don't discount the second feed as unsubstantial, just cause it's not visual for now...
Good luck with your meeting - hope you all get an outcome that is agreeable.