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ERS-1 for mapping jetties effects on shoreline change
Maged Marghany
Faculty of Science and Technology
College University Science and Technology Malaysia
21030 Kuala Terengganu, Malaysia
mmm@uct.edu.my,
magedupm@hotmail.com
Abstract
Coastal hazards such as erosion are induced by the effects of wave force or the effects of the coastal engineering structures. Coastal engineering structures such as jetties could trap a sediment transport along the coastline. This could induce erosion in the down stream. The aim of this study is to model the jetties effects on shoreline change along the coastal water of Chendering, Malaysia. The numerical model will be based on the change of wave spectra extracted from ERS-1 data. For this purpose two-dimensional Fourier Transform was applied on window size of 200 x 200 pixels. The quasi-linear model was employed to model volume change of sediment transport function on ERS-1 significant wave height. The result shows that the erosion occurred in the south of Chendering with rate of change of 4 m/month. It can be said that ERS-1 data are able to predict shoreline evaluation along the coastal structures. The jetty induced a dominant erosion on the south of Chendering. This is due to that jetties-trap sediment in the north of Chendering, which lead to erosion in the south of Chendering
Introduction
Coastal engineering studies by remote sensing have not been yet established. This is because of the fact that scientists do not used the full operational ca-abilities of remote sensing to coastal and environmental studies. There are plenty of problem raised up along the coastal waters. Most important problem is poorly understanding the interaction between wave dynamic and coastal structures. This leads to shoreline change. Scientists could not establish an excellent solution to erosion due to coastal structures. This could be due to the unrelated laboratory experiments to the nature. These experiments are unable to cover many factors of interest and are unable to investigate the wave interaction with coastal structures on a large scale. For instance, laboratory experiments can not be established any broad concept relating wave spectra and their effects on shoreline change.
It is will known that hard coastal structures (jetty, breakerwaters, etc.) placed amidst a sedimentary coastline with obliquely incident waves can induce erosion of the downdrift shoreline. According to Kraus [1] this effect can occur via impoundment of the ambient littoral drift against the structure. Coastal erosion occurs due to the effects of the coastal structures such as jetty, which is an interesting topic between scientists. Kraus et al., [1] and Hanson et al.,[2] used a numerical model of waves in order to predict shoreline change due to the present of breakwater. Kraus et al., [1] found that the accumulation of the sand was began to take place as the breakwater progressed and by the time the latter were completed, nearly 370,000 cu. yds. of sand were found deposited in the harbor.
Microwave remote sensing such as the Synthetic Aperture Radar (SAR) has been proven accurate for recording wave spectra image over the ocean. SAR data assimilation in real time could be a major tool for wave modeling and forecasting. The sediment transport due coastal structures could be modeled by SAR. This is because the fact that SAR data are able to investigate the interaction of ocean wave with coastal structures in real time. This is because that SAR allows a nearly instantaneous coverage of large areas with a fairly high resolution.
Here we address the question of whether SAR can investigate the shoreline change due to jetties effects. The main objective of this study to model the jetty effects on shoreline change to along coastal water of Chendering, Malaysia by using SAR data.
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