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Flood Recovery
MACLEAN LEVEE IN FOCUS FOLLOWING MARCH 2022 FLOOD
A high-resolution hydrographic survey has been undertaken of the Maclean Levee to determine its underwater condition following the March floods this year. Council’s geotechnical advice has found that the levee between McNaughton Place boat ramp and the northern end of the levee bank in Maclean is in generally good condition. Following this year’s event, Council has updated its flood model which was last reviewed in 2013. It will now be calibrated according to the March 2022 event including consideration of the newly built Pacific Motorway. The updated design flood levels will be included in Council’s Floodplain Risk Management Plan for the Lower Clarence. The flood model will also be used to assess levee overtopping in Grafton, South Grafton and Maclean. The previous overtopping study dates from 2010 and the review will assess any changes in levee overtopping from the new bridge in Grafton and the Pacific Motorway. When the March 2022 flood peaked at 3.36m, for 20 hours only one thing stood between the township and major inundation – sandbags. People power helped on the Tuesday night of 1 March 2022. Large scale sandbagging of the levee was not initially considered based on the flood procedures manual and major flood warnings issued in the preceding 24 hours by the Bureau of Meteorology which predicted a maximum peak height of 3.30m. The Clarence River peaked at 3.36m around 10.30pm at the flood gauge location, and further downstream at the lowest point of the earthen levee around midnight. The flood peak was approximately 60mm above the levee, but thanks to the sandbags, overtopping did not occur. “The amazing community response and assistance has given confidence that, were a similar height flood forecast in the future, it is possible to raise the levee within the required timeframe,” Clarence Valley Council Manager Water Cycle Greg Mashiah said. In early September Council’s outdoor staff laid topsoil and turf along the two sections, each about 100 metres in length, which will further consolidate the emergency works carried out during the flood. Meanwhile, the remaining sandbags along the levee are being removed, with the sand left behind to artificially raise the levee height. The State Government through Public Works is currently assessing urban levees across NSW through the NSW Flood Levee Repair and Maintenance Program and it is hoped council will be able to raise the levee as part of this program. “Council aims to secure funding to raise the levee in order to provide greater protection. In recognition that levees will, at some time, be overtopped,” Mr Mashiah said.
