Figure 33: The Manning River floodplain, 20 March 2021
With such a big catchment, floodwaters from the mountains flow down the Manning channel with great force, especially in the constrained channel of the Manning above Wingham, then spread out across the estuary where the energy is dispersed but inundation of low-lying land becomes more of a problem. MidCoast Council’s approach to flood management is set out in the Manning River Floodplain Risk Management Study and Plan (BMT WBM 2019). The plan covers the low-lying floodplain area downstream of Wingham. The study addresses both mainstream flooding of the Manning River and the impact of climate change in the form of increased rainfall intensities and sea level rise for the following scenarios: • Predicted increased rainfall intensity: modelled 10% and 30% increased rainfall • Sea Level Rise (SLR): +0.28 m by 2050; and +0.98 m by 2100. The Floodplain Risk Management Study (FRMS) has derived an appropriate plan of measures and strategies to manage present and future flood risk in accordance with the NSW Government Floodplain Development Manual. These include flood modification measures, property modification measures, risk modification measures and emergency measures (e.g. evacuation, sandbagging). MidCoast Council works closely with the NSW State Emergency Service to establish flood triggers for emergency situations. The FRMS has also identified a Flood Planning Area for the Manning River floodplain. Development of land within the Flood Planning Area is restricted and controlled by Council due to the hazard of flooding. In defining the Flood Planning Area in the MidCoast LGA, Council has considered a future flood scenario that has accounted for climate change in the form of increased rainfall and sea level rise in a combined riverine flooding and high tail water scenario to the 1% Annual Exceedance Probability (AEP, 1 in 100-year event) plus a freeboard of 500mm. The Manning River Floodplain Risk Management Study and Plan is therefore the appropriate management tool for flooding within the geographical extent of this ECMP. Related Issues: erosion and sedimentation; climate change Stakeholders: MidCoast Council; NSW State Emergency Service; Adapt NSW; Department of Planning, Industry and Environment, residents, farms and businesses on the floodplain. Photo: Evan Vale
Manning River Estuary and Catchment Management Program (ECMP)
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