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GIS as a Tool to Identify a Coastal Sediment Management Option using Remote Sensing - A Study of Songkla Bay in Southern Thailand
The correlation between change in coastal extent and sediment volume for the period 1977 - 1990 indicates that a weak relationship exists (r2 0.377), and that no linear correlation through the origin exists between the data from 1950 – 1977(figs3 & 4). The behaviour of two sets of data appears insufficient to use a single model to enable estimation of sediment change by linear shift in the coastline. However, a look at the two data sets indicates that the 1950 – 1977 data has shown a decrease in shoreline sediments, irrespective of the direction of shoreline movement. The behaviour of the sediments from 1977 – 1990, although with significant scatter, shows a relationship closer to linear through the origin. The scatter in the results could be that, at such a fine spatial resolution, coastal sediment dynamics play a major role in the relationship between shoreline length and the associated sediment volume change. In addition, the One Line model concept is said to be valid only at coarser spatial resolutions. Therefore, to investigate the effects of spatial scale on the study, the data was re-sampled for beach cells of 500m width and 1km width, and then fresh relationships were extracted (figs.5 –8). The correlations illustrated for the resampled data show that for the period 1977 – 1990 the correlation improves as the spatial resolution becomes coarser (@500m R2~0.45). Although at the 1 km level the correlation is sufficient to allow estimation of sediment volume from the shift in the linear extent of the coastline, it may be necessary to extend the study area for a conclusive regression. The 1950 – 1977 results showed a clearer relationship when aggregated to 500m and 1km shoreline cells. This relationship indicated that the shoreline shift and variation of sediment volume follows a linear trend that does not fall through the origin (@500m, R2~0.6).
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Figure 3 Scatter plot showing the relationship between coastline shift and change in sediment volume between 1950 - 1977
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Figure 4 Scatter plot showing the relationship between coastline shift and change in sediment volume between 1977 - 1990
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Figure 5 Scatter plot showing the relationship between coastline shift and change in sediment volume between 1950 – 1977 for beach cells resampled to 500m width
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Figure 6 Scatter plot showing the relationship between coastline shift and change in sediment volume between 1977 – 1990 for beach cells resampled to 500m width
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