Sea Level Rise
The City of Botany Bay Council is committed to working with its community to identify and respond to emerging hazards and risks associated with sea level rise (SLR). We are committed to preparedness and adaptation responses informed by environmental, social and economic sustainability.
Sea Level Rise Predicted Levels
Due to climate change global average sea levels are projected to increase, however, as sea levels vary across the globe, regional changes along the eastern Australian coastline are expected to be larger. Sea level rise is expected to expose low-lying coastal areas to increasing inundation over the next Century.
The NSW Government benchmarked the expected sea level rise, relative to a 1980-1999 reference period, to be:
- 0.4m above the Australian Height Datum (AHD) by 2050; and
- 0.9m above AHD by 2100.
This was contained within the 2009 NSW Sea Level Rise Policy. However, in 2012 the NSW Government withdrew this advice to allow councils the flexibility to consider local conditions when determining local future hazards. In 2012 the Government stated that it would provide information on available sea level rise projections to assist councils to develop projections relevant to their local area, however, to date this has not occurred.
Sydney Coastal Councils Group Inundation Mapping for City of Botany Bay
A study has also been undertaken by CSIRO and Sydney Coastal Council Group (SCCG) (of which City of Botany Bay is a member) which focused on the evaluation of sea level inundation along the Sydney coastal and estuarine regions under current and future sea level rise conditions for the councils who are members of the SCCG. This used the projected sea level rise benchmarks specified in the New South Wales Government Sea Level Rise Policy mentioned above.
An assessment of inundation due to the sea level rise utilising tides and storm surge was undertaken using elevated sea levels encountered during storm events. The focus of this study was the development of maps showing the inundation that arises from the contribution of storm surges and astronomical tides to extreme sea levels, which are referred to as storm tides.
Two maps show the scenarios in the City of Botany Bay Council local government area. These are:
- Map 1 - the 1 in 1 year storm event with a 40cm sea level rise (estimated to be encountered in year 2050) and a 90cm sea level rise (estimated to be encountered in year 2100) and
- Map 2 - the 1 in 100 year storm event with a 40cm sea level rise (estimated to be encountered in year 2050) and a 90cm sea level rise (estimated to be encountered in year 2100).
Council's Sea Level Rise Policy
Council resolved in February 2014 to continue to apply the 2009 Sea Level Rise Policy benchmarks of 0.4m above the Australian Height Datum (AHD) by 2050 and 0.9m above AHD by 2100 relative to a 1980-1999 reference period in preparation of planning instruments, policies and flood studies and to use the Sydney Coastal Councils Group (SCCG) Inundation Mapping in planning assessments, policies and flood studies.
Council resolved on 24 June 2015 to endorse a Policy on Sea Level Rise. The Policy on Sea Level Rise reinforces Council’s position on sea level rise by the adoption and application of the sea level rise benchmarks noted above. It provides a framework to assist Council and the community to respond to emerging sea level rise hazard and risk. The draft policy was exhibited from 12 August 2015 until 11 September 2015. Council adopted the formal Policy on 28 October 2015.
Sea Level Rise - what does this mean for your development application?
Check the attached maps first.
If the property is affected then follow the following Preliminary Procedures:
- If it’s for a new single house or alterations and additions to a house etc then Council will set the habitable finished floor level. Please contact Council on firstname.lastname@example.org .
- If it’s for a subdivision of land into two or more allotments, a residential flat building, multi unit dwelling development you are required to lodge a flood study which takes the sea level rise into account with your DA. You will also be required to lodge a risk management plan.
- If it’s for industrial/commercial or change of use then a Risk Management Plan.
A Risk Management Plan is to minimise the exposure of development to coastal risk and provide management responses and adaptation strategies to identify and manage risk and coastal hazards associated with the following:
- The safety of future workers and occupants on-site;
- The safety of the public off-site;
- The safety of adjoining properties;
- The safe evacuation route during storm and flood events; and
- The freeboard above the flood planning levels.
If you have any questions or need assistance relating to this matter, please contact Council's Strategic Planning Team on 02 9366 3666.