Survey data used to monitor beach erosion patterns
Ever wondered how beach erosion is monitored in the Tweed? It might be more hands-on than you think.
Every six months when ocean conditions are good, Council borrows an inflatable rescue boat (IRB) from the Cudgen Headland Surf Club and meets early on Kingscliff Beach.
After completing a thorough safety check, two Council officers launch the boat.
A surveyor in a wetsuit and fins then wades into the ocean, carrying a prism on a long pole. Meanwhile, a small survey team with instruments takes its position at a fixed point on the beach.
The surveyor in the water wades out on a predetermined line, placing the pole on the ocean floor at set points, allowing the prism to signal back to the survey station on the beach.
The information from each point is recorded, allowing Council to map any changes in sand levels since the last survey.
Registered Surveyor Mitch Liddell travels out approximately 500 metres, being guided by the officers in the IRB and stopping every 20 to 30 metres to secure the pole and ensure the surveyors onshore can pick up the signal.
“The measurements are used to work out the depth of the sea floor, helping to determine how much sand has moved since the last measurement and how much sand will stay on the beach, according to differences and patterns in previous records,” Mr Liddell said.
Council’s Senior Engineer – Civil Design, Warren Boyd, said the survey is repeated from four fixed positions along Kingscliff Beach and five positions on South Beach. Provided ocean conditions remain good, the entire survey takes a day to complete.
“Collecting this data helps create a timeline that reveals what is really happening below the waterline,” Mr Boyd said.
“We started monitoring when the erosion was quite severe in 2011 due to swells coming from the east and north-east rather than the south, but we also have historical monitoring dating back to the 1970s to compare today’s levels with.”
Council’s Manager Design, Paul Morgan, said surveying was a key element in nearly every job undertaken.
“Before every project, be it a bridge, road, carpark, waterway or major stormwater system, the survey team examine and record the area and its features to construct a map, plan or description for the next steps,” Mr Morgan said.
“Monitoring and profiling beach erosion is no different.”
Courtesy: Tweed Shire Council Newsroom
Tuesday 3 May, 2016
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