Byron Bay; Managing the Triple Threat Rachel Jensen, James Flockton, Jo Tinnion Brisbane, May 2015 A Floodplain Risk Management Study for Catchment Flooding, Strom Surge and Local Stormwater

Byron Bay and Belongil Creek Catchment

Belongil Catchment Catchment Flooding Storm Surge Local Stormwater ICOLLIsolation Risk Low Hydraulic grade Existing Drainage System

Mitigates storm tide dominated events (<20 year ARI) Worsens catchment flooding for rainfall dominated events (>100 year ARI) Closed Creek Entrance Trained Open Creek Entrance Worsens storm tide dominated events (<20 year ARI) Reduces catchment flooding for rainfall dominated events (>100 year ARI) May increase inundation risk from sea level rise Significant ecological impacts ICOLL Entrance Strategy Training of the entrance was not carried forward Instead: ICOLL Entrance Strategy, for occasional manual opening based on triggers

Drainage Strategy Byron Bay town stormwater drainage system capacity <1 year ARI (SMEC 2010) Low hydraulic grade Concern regarding overreliance on pumps and levees Increase in flood immunity for specific localised areas Introduction of wetland near Clarkes Beach Reduces pumps Improves water quality

Drainage Infrastructure Maintenance Low hydraulic grade and existing network capacity Annual Maintenance of major drainage lines Methods depend greatly on the surrounding vegetation and acid sulfate soil class Primary impact in smaller, more frequent events

Evacuation Strategy Quick Catchment response time (<24hrs) Evacuation routes to Belongil Spit closed in events <10 year ARI Realignment of evacuation route Prioritisation by SES of Belongil Spit Additional rainfall gauge located in St Helena, to facilitate advance warning

Summary ICOLL Entrance Strategy Drainage Strategy Drainage Maintenance Evacuation Strategy Catchment Flooding Storm Surge Stormwater

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