Year

2020

Degree Name

Bachelor of Environmental Science (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Colin Wodroffe

Abstract

Macrophytes (mangroves and saltmarsh) provide important ecosystem services which contribute to the overall health of estuaries. As such their extent and distribution are used as key indicators for overall estuary health. GIS has been used by coastal managers to determine the extent and distribution of macrophytes. Constant advancements in technology bring about new techniques and methods for mapping, often rendering older methods obsolete. Utilising GIS, the extent and distribution of mangrove and saltmarsh communities within the Minnamurra River and less studied Crooked River were assessed. Current 2020 mapping of mangroves and saltmarsh communities using high resolution aerial photography was conducted. Changes in the extent of mangroves and saltmarsh between 1960 and 2020, were determined using aerial photographic interpretation. A comparison between the use of high-resolution aerial photography and ultra high-resolution drone photography within the Crooked River was also conducted. Analysis identified that there are currently 167.99 ha of mangroves and 23.14 ha of saltmarsh within the Minnamurra River. Within the Crooked River there are currently 0.37 ha of mangroves and 3.37 ha of saltmarsh. The encroachment of mangroves and expansion of Casuarina into saltmarsh was noted to have occurred across both rivers. A number of mechanisms were proposed for the observed mangrove encroachment including sea level rise, subsidence and auto-compaction, altered nutrient regimes resulting from agricultural practices and altered tidal regimes as a result of extended periods of estuary closure. Comparison between the use of high-resolution aerial photography and ultra high-resolution drone photography, showed an overall greater precision for the digitising of mangroves with the use of drone photographs.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.