Application of Headland Control with Nourishment on a Hualien Coast

• Main Authors: Hsia-lan Chiou, 邱筱嵐
• Other Authors: Joho R.C. Hsu
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/03573262631687943805

碩士 === 國立中山大學 === 海洋環境及工程學系研究所 === 92 === The Nanbin-Beibin beach (South-North beach) at Haulien city on the east coast of Taiwan was probably in a dynamic state close to stable, prior to the completion of the Eastern Breakwater extension for Hualien harbor. Since 1987, this beach has begun experiencing adverse effect of the breakwater extension, with erosive trend continuing at Huazern beach and Nanbin Beach, accompanying by accretion at Beibin. Government authorities have constructed seawalls, submerged breakwaters and applied several types of precast concrete blocks to protect the eroding section of the coast. This study investigates the beach processes at Nanbin-Beibin Beach, starting from its oceanographic and climate condition, beach changes in the past four decades, to the protective countermeasures installed. With large-scale geomorphic approach, it is expected that combining headland control with nourishment could provide local residents and tourists with a harmonious semi-natural coastal space. This report contains the discussion on SBEACH－software for beach changes induced by storm waves, headland control with stable bayed beach and artificial nourishment; followed by description of shoreline protection at Nanbin-Beibin Beach, and finally a proposal for improving the beach stability. The study follows some of the known principles and software available in the field of coastal engineering today. Firstly, stability of the Nanbin-Beibin Beach in relation to the total length of the Eastern Breakwater of Hualein harbor is assessed by MEPBAY software recently developed for the application of parabolic bay shape equation. Secondly, a rational beach retreat is calculated using SBEACH software, which is to be used as a minimum buffer width for a proposed bayed beach using MEPBAY. Thirdly, headland control approach is suggested using artificial headlands in a curved shape rather than the traditional straight groin and detached breakwater in narrow gaps. Finally, total volume of the fill materials and budget are estimated, in order to enhance the applicability of this study. By implementing MEPBAY, it can be found that the stability of Nanbin-Beibin Beach will transform from unstable natural re-shaping to static equilibrium, using an upcoast control point 150 m short off the tip of the Eastern Breakwater. Thus, the eroding potential to Nanbin Beach could be effectively removed, and the local erosion may then become manageable. In this way, part of the precast concrete units forming the submerged breakwaters in front of the seawalls at Nanbin Beach may be taken out for construction of new detached or submerged units or artificial headlands elsewhere at Beibin Beach. The entire detached breakwater system should then be re-designed with a widened gap between units combined with bayed beach in static equilibrium and nourishment. Sufficient buffer width should be provided to all the static bay shapes so implemented. It is envisaged that the geomorphic approach considered in this report may help devise a plan to restore the eroding beach at Hualein.