Kiama seawall and walkway marine habitat assessment

Challenge

Portions of the old Kiama Boat Harbour seawall and public walkway had stability concerns. New South Wales Crown Lands proposed to replace the seawall and public walkway and replace it with a new seawall as well as new accessible ramps, public furniture, and updated landscaping features. A review of environmental factors (REF) was required for the works.

To inform the REF a detailed Marine Habitat Assessment (MHA) was required. The objective of the MHA was to; describe the existing marine environment within the area and determine the potential marine biodiversity constraints to the proposed works, determine the potential impacts of the proposed works on the marine environment and on any habitats and/or flora and fauna species of conservation significance occurring or likely to occur within the study area. Where appropriate, recommendations were required on mitigation measures to avoid, minimise and mitigate impacts on the marine environment.

Solution

To inform the Marine Habitat Assessment, our Marine Science team used a combination of techniques including an underwater remotely operated vehicle, in water survey techniques and spatial interpolation models to develop a detailed understanding of the marine environment within the survey area.

As part of the survey, a bed of high-density seagrass including Posidonia australis and Zostera capricorni as well as a range of fish species (e.g. dusky flathead, luderick and rock cale) and habitats (i.e. low relief reefs and unconsolidated soft sandy sediments) were recorded.

Using the results of the survey, and our understanding of the potential impacts to the marine environment that could occur due to the proposed works, our team worked with the client to develop practical mitigation measures to avoid, minimise and mitigate potential impacts on the marine environment.

Impact

Based on the Review of Environmental Factors for the project that was informed by the Marine Habitat Assessment, our client was granted approval to undertake works required to update and modernize the seawall within Kiama Boat Harbour.

The works to update and modernize the seawall within Kiama Boat Harbour works were completed in 2023. Based on initial assessment no impacts to seagrass or other marine receptors occurred due to the works.