COASTAL HAZARD

Byron Shire Council’s Staff Report on the Planning Proposal states:

The applicant has commissioned a detailed Coastal Hazards Assessment, which provides contemporary modelling to establish the likely location of the erosion escarpment in years 2050, 2070, 2100 and 2120.
The modelling approach, which includes allowance for sea-level rise, was agreed by staff of the Department of Planning, Industry and Environment Coastal Division, and forms a sound basis for the hazard assessment.
The modelling shows that the contemporary 100 year hazard line (i.e. for the year 2020) is located approx. 135m seaward of the previously mapped 100 year hazard line, which was used as the basis of the 7(f1) Coastal Land zoning and associated DCP Part J erosion precincts. The previous mapping was based on analysis from the 1970s.
The contemporary modelling demonstrates that the area within the site that is subject to coastal hazard is far smaller than previously understood.

Royal HaskoningDHV, the coastal management experts who undertook the recent study, also undertake work for Byron Shire Council and many other NSW coastal councils. Their methodology was peer reviewed and agreed to by both Council staff and staff from the Department of Planning, Industry and Environment Coastal Division. The results were also peer reviewed and accepted by all parties. There is no conjecture, no disagreement or grey area about the findings of the coastal hazard assessment.

The results are consistent with the Byron Shire Coastline Hazards Assessment Update prepared by BMT WBM for Byron Shire Council in 2013. The findings of this study have not yet been included in any updated coastal hazard planning controls for Byron Shire. Planning controls remain based on the 42 year old 1978 Byron Bay – Hastings Point Erosion Study. The 1986 DCP is also based on this 1978 work.

Recent aerial photography also supports the findings of the 2013 and 2019 studies.

The 2020 Royal HaskoningDHV report uses probabilistic modelling, which is widely accepted to be the best practice approach to understanding future coastal hazard. The parameter values are randomly sampled one million times and combined repeatedly as a means of predicting the shoreline position (extent of coastal hazard) at particular times in the future. The study used a 2020 (100 year) horizon and a 1% exceedance factor. This is the most conservative position and has been adopted in the planning proposal.

Subject site showing 1988 coastal hazard line and updated coastal hazard lines from 2013 and 2019 studies