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ANTELOPE REEF AND KUANGZAI CAY (CRESCENT GROUP) 16°27’50.03”N, 111°35’19.51”E
Geographic area
Intertidal and submerged area
Human infrastructure
Land area above water
GeoEye-‐1 18 Feb. 2013 Sea Level: +16cm ©DigitalGlobe 2013
Antelope Reef is a coral atoll in the southwestern part of the Crescent Group, a submerged atoll in the western part of the Paracels, located just over 143NM southeast of the island of Hainan and under 170NM northeast of Vietnam’s mainland. The closest shallow geographic features within the Crescent Group are Robert Island, less than 1NM northeast, and Money Island, less than 2NM west. Outside the Crescent Group, the closest shallow geographic feature is Discovery Reef, less than 12NM south. The atoll of Antelope Reef extends over 6km along its northwest-‐southeast axis and close to 4km along its west-‐east axis.
There is one built-‐up above-‐water area with scarce shrubs on the southeastern outer edge of the reef flat. The built-‐up area extends 100m by 60m; the overall above-‐water area in the 18 February 2013 satellite image covers an area of 37,000m2
and is over 300m by 100m. Other satellite images viewable on Google Earth (from 4 May 2004, 10 May 2006 and 2 April 2014) suggest that the sandy part of the northwestern and southeastern sides of this above-‐water area changes shape and size under the combined effect of astronomic tides, storm surges and wind-‐waves. Satellite images also show that this above water area is surrounded by sedimentary rocks which may be mostly above water. Numerous sand banks are visible along the eastern side of the reef flat (along the central lagoon of the Crescent Group), many of which have awash and above-‐water sections that are smaller than Kuanzai Cay. Based on the assumption that the 18 February 2013 satellite image was captured when the sea level was 16cm above sea level, it is expected that the sea level increases by 61cm at Mean High Water Spring, at which stage of the tidal cycle it will cover the sand banks partly if not entirely. Evidence of strong hydrodynamic forces that are visible in the morphology of the reef flat in this satellite image and in others viewable on Google Earth suggests that these sand banks are dynamic. In the 18 February 2013 satellite image, over 30 man-‐made structures can be counted on Kuangzai Cay. They are built on barren sandy ground, in close proximity to one another but in no apparent order. The aerial coverage of the overall reef platform is 17.12km2 comprising the reef flat of 9.43km2, the reef slope of 2.12km2 and the lagoon of 5.54km2. The outer part of the reef flat, located along the reef slope, is 0.9-‐1.4m deep at Mean Sea Level, except around the sand banks, where it is shallower. It is expected that the parts of the reef flat that are less than 1m deep at MSL will be exposed at Lowest Astronomical Tide. A sandy back reef extends over 800m on the western side of the reef flat, between the lagoon and the shallow outer edge of the reef flat. The lagoon is characterised by a dense reticulate reef system and is 5-‐6m deep. The reef slope extends mostly 100-‐300m. Over 15 small boats (5m-‐long) are visible on Kuangzai Cay, beached on dry sand; another 10 or more can be observed over the reef flat, along the southwest-‐facing side. Mariculture cages are also visible in the northern part of the lagoon (when zooming in on the high resolution satellite image) and dredging marks (98,000m2) are visible on a shallow part of the back reef, north of Kuangzai Cay.
Land area above water
ANTELOPE REEF AND KUANGZAI CAY (CRESCENT GROUP) 16°27’50.03”N, 111°35’19.51”E Derived from GeoEye-‐1 satellite data captured on 18 February 2013 [Sea Level: +16cm] Bathymetry Map
Habitat Classification and Land Cover Map
Kuangzai Cay
Kuangzai Cay
