'Coastal lakes and estuaries' landscape group

Qualitative models were developed for subtidal benthos and intertidal wetlands, reflecting the continuum between fully submerged environments (‘Seagrass’ landscape class) and intermittently submerged environments (‘Saline wetlands’ landscape class) that are present within estuarine ecosystems. The qualitative model for subtidal benthos reflects expert opinion that seagrasses are particularly sensitive to subsidence resulting from underground mining, which leads to an increase in the depth of water above the seagrass beds and reduced light penetration. Only one (Chain Valley) of the three additional coal resource developments in this area is under a coastal lake. The delineation of subsidence control zones and requirement that mining components prepare subsidence management plans since 2004 (Mills, 2009) are regulatory measures intended to avoid or limit subsidence in the shallow, fringing zone of the coastal lakes, by restricting coal extraction options in these vulnerable areas. No quantitative model was developed for subtidal benthos based on an assessment that impacts on seagrasses from the additional coal resource developments were likely to be negligible.

The qualitative model for intertidal benthos identified an interaction between groundwater and saltmarsh. Saltmarsh tolerates less inundation than mangrove, and groundwater extraction can potentially result in subsidence owing to reduced soil volume and more prolonged inundation (Saintilan et al., 2009), which would favour mangrove over saltmarsh. Both saltmarsh and mangrove provide similar ecosystem services although the model indicated the saltmarshes could be preferred roosting habitat for migratory wading birds. Subsidence of saltmarsh resulting from groundwater removal is of the scale of millimetres (Rogers and Saintilan, 2008), which is a much finer scale than modelling undertaken as part of the BA. The impacts of such fine-scale processes were judged to be so local and uncertain that no quantitative model was developed for intertidal benthos.

The very small areas of the ‘Creeks’ landscape class (<0.1 km2) are upstream of any development; hence there is little potential for development to directly impact on these streams and no qualitative or quantitative models were developed.

The small areas of the ‘Barrier river’ landscape class within the zone of potential hydrological change are all upstream of the tidal limit and overlap with the distribution of perennial rivers defined in the ‘Riverine’ landscape group. Hence, no model was developed for the ‘Barrier river’ landscape class.

Last updated:
18 January 2019
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