Byron Bay; Managing the Triple Threat

Rachel Jensen, James Flockton, Jo TinnionBrisbane, 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

SummaryICOLL Entrance

Strategy

Drainage Strategy

Drainage Maintenance

Evacuation Strategy

Catchment Flooding

Storm Surge

Stormwater

Thank You