No abstract

No abstract

Large numbers of people live along and depend upon the world's coastal resources. Human modifications of the coastal zone, in combination with climate induced environmental changes, have had a major effect on the natural ecological systems. GIS analysis of remote sensed data, combined with fieldwork and laboratory tests, can be used to determine the resultant eco-geomorphic changes that need to be managed sustainably on a worldwide scale. Modelling the eco-geomorphic dynamics between 1949 and 2016 on the Wandandian Creek delta (southeastern NSW, Australia) provides a case study of management options for such coastal resources. Results from the Wandandian Creek delta show that sand/silt sediment derived from the partially (22%) modified terrestrial catchment has prograded into the wave-dominated St. Georges Basin where it is impacted by nearshore processes. Clear spatio-temporal growth of the areal extent and elevation of the deltaic levees and sandspits, with their associated mangroves and saltmarshes, has occurred over the past 65 years. Although the growth rate has fluctuated during the study period, due to flood events in 1974, 1990s and 2010, the overall subaerial and subaqueous delta area has had an average growth of 4168 m 2 annually with the shoreline extending 1.451 m/year on average. This geomorphic growth has stabilised the estuarine deltaic habitats with high proportions of nutrients and organic matter, particularly within saltmarsh, mangrove, Casuarina/Juncus and other mixed native plant areas. This research shows the importance of analysing morphological changes observed on the delta that can be related to both anthropogenic modifications and natural processes to the catchment and thus should be used in the development of catchment and coastal management plans.

Coastlines are dynamic environments, with their Eco-geomorphology controlled by a complex range of natural and anthropic processes. Estuarine environments and associated wetland ecosystems are a critical shoreline types with regards to biodiversity, and are particularly susceptible to the influence of sea-level rise. This project applied future sea-level rise of Intergovernmental Panel on Climate Change (IPCC) hydro-scenarios to assess its impact on the ecogeomorphic aspects of coastal ecosystems in terms of risk assessment and sustainability. Comerong Island is used as a case study and is compared with other surrounding ocean-influenced and lagoonal deltas to assess the regional effects of sea-level rise. Applying the IPCC scenarios to the chosen geomorphic coastal data-sets resulted in a hydro-geomorphic model that shows the study site was already under pressure in 2015, with significant land area projected to be lost by 2050 and 2100. These findings are also expected to occur across the remaining estuaries in southeastern Australia. Applying this broad-scale, multi-strand application of geoinformatics simulation (GIS & RS), together with the various IPCC sealevel rise scenarios, will be necessary to assess future ecosystem sustainability management plans for coastal zones worldwide.

Extensive research into the evolution of wave-dominated estuaries has been documented since the 1960s. However, there has only been limited research on the prograding bay-head deltas that are the primary drivers for the rate and stage of estuary evolution. This paper presents the findings of a highresolution spatial study into the evolution of the Macquarie Rivulet bayhead delta in the Lake Illawarra barrier estuary. The delta's evolution has been established based on sedimentological analysis of 74 cores, two 14 C ages and 45 amino acid racemization ages. This study intersected two Pleistocene and 10 Holocene sedimentary facies associations representing both the retrogradational and progradational phases of delta development. The distribution of bayhead delta facies associations in shallow barrier estuaries is initially controlled by the antecedent morphology, but, in contrast to deeper estuaries, this influence decreases as sedimentation proceeds. Changing relative sea level also has a major control on facies distribution with transgressive facies deposited as relative sea-level rises being replaced by prograding deltaic facies during the highstand and subsequent minor relative sea-level fall. Fluvial sediment supply and river flood events affect the rate of delta progradation, and produce low and high flow sediment deposits within the overall deltaic sequence. The low tidal flux in barrier estuaries, the muddy cohesive nature of the sediments and the prevalence of bioturbation means that primary sedimentary structures are rarely preserved in these bayhead delta facies. The depositional model of bayhead delta evolution shown by the Macquarie Rivulet delta would be widely applicable to other similar barrier estuary settings.