圖書典藏及影音數位平台

花蓮海岸地區係菲律賓海板塊與歐亞大陸板塊碰撞後，引發之陸生運動所形的陸地，加上河流及海浪之侵蝕作用，陡起陡落的山巒與峽谷，曲流、河階等地形；在海岸地區則雕鑿出變化多端的珊瑚群礁和海蝕地貌。由火山島弧推擁而成的海岸山脈，為呂宋火山島弧北延的部分，由島弧安山岩質岩漿凝固而成的中新世至上新世火山岩與含火山源的海相沉積岩所組成。不僅火成岩的地質結構異於中央山脈，其地形更是險峻，地理景觀獨特。花蓮海岸分佈海岸階地、沙灘、礫石灘、礁岸、離岸島、海岬和海蝕平台、海蝕洞、海蝕溝等海蝕地形，並在板塊持續擠壓下影響陸地隆升， 地形相當發達。 花蓮一般性海堤歷經多年風吹日曬、颱風豪雨及多次強弱地震影響，恐有略呈堤頂下陷、淘空滲砂與材料劣化等現象發生，對於現況防洪構造物的安全性影響極大，威脅居住於花蓮海岸人民生命財產安全。然而全段拆除重建工程經費龐大，且花蓮一般性海堤多屬老舊堤防，為能尋求有效維修與補強方案，擬藉由堤防結構安全檢測計畫來全面檢視花蓮一般性海堤之安全，以利後續維護管理，其堤防構造物安全性之評估分析實為當務之急 本計畫主要目的為暸解花蓮一般性海堤內容結構現況，先以人員目視進行檢查並提出期初報告，後續採用非破壞檢測方式如透地雷達探測、震波測勘等非破壞檢測方式，檢查堤防構造物之使用狀況與內部損壞狀態，包含結構體內部裂縫及含水狀況等情形，以便未來做為堤防管理、維護之參考依據，以及尋求有效維修與補強方案，擬委外辦理堤防結構安全檢測分析及研擬改善方案。

The general coastal structures (seawalls, submerged breakwater, coastal protection work, and training jetty) in Hualien have suffered exposures to wind, rain, typhoon, and earthquake for many years, those phenomena could include subsidences at the top of seawall, seawall erosions by sand, and constructure deteriorations. In order to defend against the climate change and extreme weather, protecting people life and property safety against typhoon waves in Hualien coast is the perpose of this project in this year. For the seawall safety assessment, the visual inspection was firstly estimated. Secondly, the non-destructive mode including ground penetration radar (GPR), supersonic way, and unmanned aerial vehicle (UAV) for seawall covering layer were conducted. Finally, the destructive mode by compression strength test from concrete drilling core for seawall inside state was evaluated in this project. By estimating the general coastal structures show that 25 seawalls are “normal state”but 2 seawalls are “noticed improvement”. Moreover, the total length of them is 13,785 m by measured in this project. By selecting historical investigations, a Hualien River System and its mainstream approximation map in A1 size were ploted from those integrated information, and the handbooks for embankments along the Hualien River and seawalls along the Hualien coast were also made. Moreover, the embankments and general seawalls of safety maintenance manuals for Hualien River System and Hualien coast were also updated for the criteria of unscheduled inspection. The context shows that “The flood discharge in the river channel reaches the Level 1 or 350 mm of accumulated rainfall at measured stations or the criteria from the investigated reports”for Hualien River System and “According to CWB measured station in Hualien, the wave height reaches 8 m for typhoon period or Tsunami”for Hualien coast, those structures would be checked for the unscheduled inspection in Hualien. For the wave and tidal simulations, the coastal sediments nearby the Nan-Bei-Bin to Huaren area occurred by wave energy concentration, wave diffraction by the breakwater of Hualien Port, and tidal current by clockwise whenever those could cause coastal erosion in this area. In addition, the interactions between waves, tidal and coastal steep topography could generate much stronger flow, which could be the main reason to lead to coastal sediments in Hualien coast.