Sampling in Geographical Fieldwork Using GIS Techniques , pp. 3 of 6

In Callaghan et al.’s (2015) investigation of coastal erosion along False Bay, South Africa, remote sensing techniques with Landsat TM/ETM+ imagery were used to monitor and detect coastal erosion, susceptibility to coastal erosion, and vegetation change along the bay. The remote sensing technology allowed for repetitive data acquisition, which was essential for monitoring changes in land cover over time. Another paper by Mitra and Basu (2016) also utilized Landsat imageries to assess coastal erosion and accretion on the dynamic coastal belt of West Bengal from Talshari to Rasulpur.

The scope of this study using remote sensing techniques was to be from years 2008 to 2016. However, due to the insufficient satellite images captured for each year, the high cloud cover and low resolution for some images, data was collected in a four-year interval, for years 2008, 2012 and 2016. Therefore, for the given time frame of the study, Landsat 7 (images from 1999 onwards) was utilised.

For each satellite image at each time period, the different bands for each image were merged using Erdas Imagine (2011) software. When the bands had been merged, the final image showed the extent of beach erosion of Cha-am’s coastline for that time period. ArcMap was used to overlay the images of different bands to produce a single image for each time frame. Using ArcCatalog, the coastline of Cha-am from images of different time periods (i.e. 2008, 2012, 2016) were digitized so as to create an outline of the coastline for each of the time periods. The coastlines for each of the time period were then overlain into a single image, with a remote sensing image of the area as the background. The coastlines were then compared to determine the extent of beach erosion and beach retreat (Yoshida, et al., 2013). Special focus was given to the coastlines of Cha-am beach and Cha-am south beach.

Figure 4 shows the Cha-am coastline obtained from the remote sensing images in the three years – 2008, 2012 and 2016, while Figure 5 shows a zoomed in image of the same area.

From the remote sensing image results in Figure 5, at Cha-am beach (‘low erosion sites’), the remote sensing imagery results show that there is no significant, observable coastline retreat from the years 2008 to 2016. The three lines (representing Cha-am coastlines in the three years – 2008, 2012 and 2016) are very much overlapping one another, which indicates that there is no significant coastline retreat or advancement recorded at that area. On the other hand, from Figure 5, at Cha-am south beach (‘high erosion sites’), the remote sensing imagery reveals that there were changes in the coastline along Cha-am south beach from 2008 to 2016. The results show that certain sections along Cha-am south beach experienced coastline retreat from 2008 to 2012 and then to 2016. Results also indicate that other sections further south of Cha-am south beach showed an advancement of coastline from 2008 to 2012, followed by a subsequent retreat of coastline from 2012 to 2016, The coastline in 2016 exhibited the most extreme retreat.

An Inspiring Quote

"[Open-mindedness] includes an active desire to listen to more sides than one; to give heed to facts from whatever source they come; to give full attention to alternative possibilities; to recognize the possibility of error even in the beliefs that are dearest to us."

~ John Dewey, How We Think

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