圖書典藏及影音數位平台

綠島、蘭嶼位於台東離島，座落於太平洋深海區域。因近岸地形坡度較陡，入射波浪能量消散有限，海岸範圍易受大浪侵襲。早期沿海區域開發有限，縱有波浪營力作用，影響居民範圍相對較小。隨著觀光資源開發及沿海基礎建設完工，沿海區域人口密度增加，每遇颱風侵襲，則增加釀災之機率，威脅沿海居民生命財產安全。如101年颱風天秤兩度經過台灣東南部海域，於綠島造成多處環島公路邊坡受損，著名觀光景點朝日溫泉及人權公園等多處設施也遭巨浪衝擊損壞。至於蘭嶼部分，機場跑道旁海堤地基則受颱風波浪沖刷淘空。

The present project in second year conducts the collection, investigation, in-situ survey and analysis on the Lanyu island field data based on the 「The Construction of Coastal Environments (2015~2010)」formulated by WRA, for updating the foundational information and datasets for Lan-Yu coasts. The dataset can be applied to plan the coastal restoration policies, maintain the existing seawalls and make the local coastal protection projects. The investigated area is located on the west (Yeyou), north (Langdao), east (Dongqing) and southwestern coasts(south side of Lanyu airport to Lanyu elementary school) on Orchid island in second year. The local coastal length is approximate 15 km. The typical working terms are the analysis and collection of foundational data, the measurement of marine bathymetry and land topography, the short-term hydrodynamic investigation, the in-situ sand-shift survey and the suggestions of coast protection. Based on the present results, including the foundational data, in-situ survey, numerical simulations, aerial photographies and field investigations, it shows that most of Lanyu coast belong the coral-reef coasts beside of Ba-Dai Bay and Dongqing Bay. Ba-Dai Bay and Dongqing Bay both are the combined gravel-sand coasts. Their geomorphic is related to the sediment discharge from the rivers during the rainy days and typhoon events. The sand source is different from that on the Green’s island. However, the potential of coast change can be not estimated due to insignificance of observation on the rivers and basic data. The high potential of coastal damage on the Lanyu island is the storm surge induced the inundation. Based on the numerical simulation with 50 years return periods, the particular section on the west, southwest and east coasts possibly occur the overtopping, but the situations are not necessary to cause the damages. The simulated results agree with the existing historical records. The numerical assessment determined by the scenario simulations considered the climate change is similar without the climate change. It shows that the influences of climate change are not significant on the Lanyu coast. Hence, it suggests the coastal management and non-engineering methods to as the main coastal defense strategies.