Development of a GIS-based Estuary Sedimentation Model

Eleanor Bruce (1), Peter J. Cowell (1), David Stolper (2)

(1) School of Geosciences, University of Sydney (AU)
(2) United States Geological Survey (US)

The ecological impact of rising sea level is a growing concern to environmental managers and researchers. Sea level rise results in increased inundation and coastal erosion, which has major implications for coastal ecosystems that form the transition zone between land and sea. Ecosystem response relative to sea level rise is dependent on sedimentation rate and consequently the maintenance of relative elevation.
Under differing sea level rise scenarios the extent and geographical location of intertidal areas and associated habitats will vary. In determining the adequacy of current reserve areas and planning mechanisms for protecting future coastal ecosystems from adverse development impacts it is critical to have an understanding of habitat distribution scenarios. Will current infrastructure developments restrict natural processes of ecological succession and limit the potential geographical range of important coastal habitats? Insight into the rates of change can assist coastal planners assess future implications of current planning decisions.
The research project presented here aims to develop a spatial model for predicting the impact of sea-level rise on remnant saltwater wetland ecosystems through Geographic Information Systems (GIS). The Homebush Bay Millennium Parklands in Sydney, Australia was selected as a case study site due to the conservational significance of the remnant wetland ecosystems present and growing management concern for the fragility of these saltwater habitats. This paper presents the conceptual framework for the model design and outlines challenges encountered in transferring the principles of a one-dimensional profile model into a multi-dimensional GIS environment. The Estuary Sedimentation Model (ESM) was developed by Stolper (1996) to simulate aggradation of intertidal zones under conditions of sea-level rise and varying rates of sediment supply. Evolution of the estuary in the ESM is governed by three factors: (1) sea level change; (2) elevation-dependent accommodation space available for sediment deposition and; (3) inundation-dependent vertical accretion of sediment. Techniques are investigated for incorporating the ESM into a GIS to provide a spatial dimension in the representation and visualisation of change. In modelling the spatial extent of sediment accretion and saltwater encroachment on wetland communities it is possible to quantify and map rates of potential habitat loss.