COLLINGWOOD BEACH COASTAL ZONE HAZARD MAPPING 2017
Shoalhaven Council has very recently revised its Coastal Zone Hazard Maps for Collingwood Beach. For those whose property is on the coast, these hazard lines can have significant (adverse) impact on the property’s value and development controls. If your property is deemed to be under threat it can even be seized by government . It is important that you understand and are aware of what these hazard lines mean to you. The Collingwood Beach Preservation Group (CBPG) actively engages with Council and has challenged the methods that have been applied to determine previous hazard lines. The simplest method is what is known as the Bruun Rule and is generally used as a rule of thumb. It should be used with caution because of the underlying assumptions and simplifications and is only suggested for use by the NSW Department of Planning and Environment in the absence of better mapping methods.
The latest sea level rise predictions adopted by Shoalhaven City Council have been modelled by consultant Advisian to determine the impact on Shoalhaven beaches. The Advisian Shoalhaven Coastal Hazard Mapping Review report utilises (in part) the survey data that the CBPG has been collating over the last few years for the Collingwood beach dunes. The Advisian report confirms the advice that CBPG has been conveying to Council staff over the years, namely that Collingwood beach is accreting (growing towards the sea). CBPG survey measurements show that the edge of the dune vegetation is now 8m further seaward of what was the Mean High Water Mark on the original subdivision built in the 1950s. The survey measurements also show that between 1974 (100 year storm event) and November 2016 some 93,165 cubic metres of sand have been deposited on the beach, and this is with the significant June 2016 East Coast Low impacting the beach in the intervening period.
The Advisian assessment has shifted the 2030, 2050 and 2100 hazard lines placed on waterfront properties by Council seaward. The 2100 line is now located off most properties. Maps of the hazard lines for Shoalhaven beaches are included in the Advisian report. The report and map can be see by clicking Advisian Report and Collingwood Beach Map.