Document ID: chunk:federal_register_of_legislation:F2015L01389:body:0:p55
Version: federal_register_of_legislation:F2015L01389
Segment Type: other
Provision Reference: 
Character Range: 159281–161996

metres. The bottom, and much of the beach, is a fine, greyish sandy silt, much of which is derived from decaying vegetation. Towards the eastern recesses this is greyer and darker, and in the north-east corner the beach is composed of a fine, dark, brownish mud. In a few places, particularly towards the southern end, the sand is replaced by a bare breccia slope and jagged fragments occur all down the west side.
Along the sheltered sides of the island, the shore is composed partly of coral shingle and partly of patches of white sand. However, periodic storms and changes in wave alignments alter the distribution of beach sand on an annual cycle. On the south and east coast (the windward sides) the bank is almost entirely coral shingle.
Hydrology
The non-marine water resources of the Cocos (Keeling) Islands consist essentially of groundwater and rainwater. Where conditions are favourable, fresh groundwater on coral islands occurs in the form of shallow lenses beneath the ground surface. Such lenses are found in some of the larger islands within the Cocos (Keeling) Islands. Due to the generally porous nature of the soils and underlying geology, there is no significant surface run-off. Run-off only occurs in localised areas where the ground is compacted and only for very short periods after heavy rain.
Preliminary investigations on North Keeling Island (Falkland 1988, 1992) indicate the presence of a very thin freshwater lens on at least part of the island. It is not known whether this lens is permanent.
Gibson-Hill (1948) states that the North Keeling Island wells were sunk to a depth of 3.6–4.5 metres before World War II when between 40 and 60 Cocos-Malay people lived there for up to three months at the end of each year, collecting coconuts and timber. The water in the wells was reported to be brackish, and was used for washing and cooking rather than drinking.
The broader western side of the island is an average 300–400 metres wide. This roughly equates to the minimum 400 metre width of larger islands on the southern atoll, which is necessary to sustain a freshwater lens on tidally influenced saltwater (Jacobson 1976).
The closure of the lagoon entrance in 2005 as a result of natural forces of deposition has led to significant changes within the lagoon habitat. Whilst the water level of the lagoon varies, depending on rainfall and evaporation, seawater no longer enters the lagoon and levels are not affected by tidal fluctuation. Without regular flushing of seawater, the lagoon will become further deoxygenated and brackish and is likely to support freshwater weeds in the shallower waters.
A positive impact of the lagoon closure is the colonisation of the lagoon entrance