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103/11/04 14:00 台灣師範大學地理學系林宗儀副教授 演講
演講公告
張貼人：網站管理員 ╱ 公告日期：2014-10-28演 講 公 告
主講人：林宗儀 副教授
地點：中央大學科學一館S-325教室
摘要：
講題：沙洲的地形動力與演育及其在海岸防災的應用
主講人：林宗儀 副教授
台灣師範大學地理學系
時間：11月04日（星期二）下午2點
地點：中央大學科學一館S-325教室
摘要：
A series of barrier islands are situated along the Tainan coast, in southwestern Taiwan, to form a barrier-lagoon system that plays an important role in coastal protection. Most of the sand barriers have become attached to the coastline during the last century due to human reclamation of the lagoon area, which has been used as breeding and fishing ponds. The Wan-tzu-liao barrier is the only island left that has retained its more natural state and could adjust itself to the changes created by coastal processes. Morphological changes of the Wan-tzu-liao barrier island are determined by analysis of historical maps, aerial photographs, and satellite images. An extensive collection of vibration cores from different sedimentary environments of the island is used to identify the sedimentary characteristics for each depositional unit. At the same time, the facies changes in the vertical stratigraphic sequences are used to speculate the possible environmental changes and explain the morphological evolution of the barrier island.
Based on the morphologic and sedimentary analyses, the major processes that control the morphological changes of the barrier island may include the following : 1) the onshore-offshore sand movement facilitated by waves; 2) the prevailing longshore drift southward; 3) the strong wind transport southward during the winter; and 4) the overwash process that moves sand landward during a storm or typhoon. A transgressive evolution model may be suitable for this barrier system. With the island migrating landward in response to the global trend of rising sea levels, this morphodynamic model predicts that the Wan-tsu-liao barrier’s landward movement may accelerate until it finally becomes attached to the continent coastline that is currently fixed at its position by a sea wall. Once the sand barrier is attached to the sea wall, it will become a sand beach at the toe of the sea wall, and, with rising sea levels, this sand beach would ultimately become submerged into the sea and lose its natural buffer ability.
In response to coastal erosion, engineering structures such as seawalls, groins, and detached breakwaters, are usually used in Taiwan to protect the shoreline and prevent the life and property loss in a hazardous typhoon event. However, the protection measures are shown to be insufficient in combating the strong waves and storm surges. Even worse, the concrete structures always leave negative effects on beach preservation. Beaches either in front of the seawall, or on the down drift side of a groin or a series of detached breakwater, disappear soon after the completion of the structure construction.
When it comes to managing coastal hazard, the rule of thumb is to live by the rules of the sea. Reinforcement or reconstruction of sand dunes with artificial planting or seeding might help sand accumulation and, thus, enhance their natural function on coastal defense of the barrier island. Combining the proper buffer with setback zoning, which limits the developments or investments in hazard-prone areas at the shoreline of the continent side, will be one huge step towards environmental sustainability and will also greatly reduce the loss of people’s lives and properties in the future.
最後修改時間：2014-10-28 PM 5:05
