| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系 === 104 === The Coastal Zone Management Act (CZMA) of Taiwan was adopted in early 2015. This act is aimed at promoting the integrated management and sustainable development of coastal areas. In terms of the details this act, article 14 indicates that a coastal protection plan shall be formulated for coastal zone erosion, tide overflow, storm surge flooding, land subsidence, or other potential disasters, implemented by the central or local government. Additionally, article 44 indicates that central and local governments need to announce their coastal management plans within two years, which underscores the importance and urgency of coastal management planning in Taiwan. This research focus on a case study conducted in Tainan, located in the south-western part of Taiwan. Shoreline change was analyzed using geographic information system (GIS) and Digital Shoreline Analysis System (DSAS) models. Resources including aerial photography, topographic maps and satellite imagery have also been used to monitor shorelines change from 1974 to 2013. Erosion and accretion conditions were recorded to identify shorelines using a statistical method called the linear regression rate (LRR). The results of the LRR suggested the Tainan coast was largely in an erosion phase. The most serious situation occurred in the sandbars of Cigu Lagoon, located in the middle of the Tainan coast. In contrast, the results suggested coastal accretion occurred along the Shinfulun sandbar and in the Sicao Wetland during the study period. An image processing method was developed to identify the suspended sediment distribution (SSD) at an instantaneous time. It was verified by comparing results with survey data from the study area. The SSD helps explain the reasons for coastal change in Tainan.
Daily satellite image derived from FORMOSA-2 were analyzed to illustrate the gradient magnitudes and directions of suspended sediment (SS). The results demonstrated that in alternative flood or ebb, the gradient directions revealed a generally westward/northwestward transport, which suggested that the offshore-ward transport of SS is likely one of the major factors in coastal erosion. In addition, these results revealed that sediment discharged from the Tsengwen River moved northward and eastward and accumulated south of the Cigu seawall. This movement therefore caused Shinfulun sandbar accretion in the north estuary of the Tsengwen River. In conclusion, the decrease in the southward supplementation of SS from northern Tainan City is likely be the crucial factor resulting in erosion along the Cigu lagoon.
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