Project - Coral Sea Mapping 2021-2022 (AIMS, Parks Australia)
- Between 01/01/2022 - 00:00 and 31/12/2024 - 00:00
This project developed a set of high quality GIS datasets of the emergent and shallow marine features (reef boundaries, reef tops, islands, and cays) of the Coral Sea Marine Park (CSMP). The goal of this mapping was to improve the precision and spatial detail of existing reef maps.
## Features mapped:
- Coral atoll platform boundary - outer visible extent (~40 - 60 m depth)
- Coral reef boundary - coral substrate, plus connected sand, raised off atoll platform, mapped to 30 - 50 m depth.
- Reef tops (5 m and 10 m depth)
- Coral cays (above mean high water)
- Coral cay vegetation
- Beach rock - around coral cays and where visible on reef tops
- Beach (high tide water to vegetation, excluding beach rock)
- Structures (wrecks, weather stations, buildings) - incomplete coverage
This project mapped reef boundaries features in a manner similar to the existing reef mapping of the Great Barrier Reef Marine Park (GBRMP) and Torres Strait (Lawrey, et al. 2016). The key characteristics of this mapping is the focus on determining the outer most boundary of coral reefs, where they rise up off the surrounding sea floor. In the Coral Sea the coral atoll platform was considered the sea floor and any solid coral structure raised up off the atoll platform was considered a coral reef. The reef boundaries also include sandy areas that connect close reef patches and surrounding sand that is highly connected to the coral substrate, as evidenced by halos (sand cleared of algae by fish around the coral patches). Patches of coral closer than 50 - 300 m were merged together to make fewer, but larger coral reef boundaries. The merge distance depended on slope, depth, structural uncertainty and visual uncertainty. The accuracy of the reef boundaries was checked by comparing digitisation of a subset of the features by independent team members. Digitised features were reviewed and refined by a second team member using additional imagery. Reef boundaries were linked with historic names based on nautical charts and historic maps, then assigned a permanent identifier that can be used instead of the reef name. Large reef features were cut into multiple segments where different sections are known by different names.
In addition to reef boundary mapping the structure of the reef tops was mapped using satellite derived bathymetry to estimate a 5 and 10 metre depth boundary. The 5 m depth reef top aligns with the existing 'Dry reefs' mapping performed in the Great Barrier Reef. Shallow features were also mapped, including coral cays, surrounding beach rock and vegetation. Additionally the beach area (above high tide, but below vegetation) was mapped to provide a proxy for potential turtle nesting areas. Finally where they were visible, man made structures along with ship wrecks were mapped, however the resolution of the imagery available meant that these features were far from comprehensive.
The features were digitised using a combination of satellite and drone imagery. Sentinel 2 (10 m resolution) and Landsat 8 (30 m resolution) imagery was used to map all marine features, drone imagery was used to map some of the cay areas, while the rest were mapped with publicly available ArcGIS World Imagery (~0.5 - 1m resolution).
The Sentinel 2 and Landsat 8 imagery were processed into cloud free composite images using the Google Earth Engine. The imagery along with the processing scripts and mapped features are openly available.
This project aims to provide a more detailed spatial map of reef features to improve planning and management of the Coral Sea Marine Park
- Lawrey, Eric
eAtlas Project Leader
Australian Institute of Marine Science
e.lawrey@aims.gov.au
- marine
- MARINE
- Regional Seas | Coral Sea