圖書典藏及影音數位平台

宜蘭縣位於本省東北部，面臨太平洋，海岸線全長約 106 公里，其中沙質海岸北起頭城南至蘇澳約33公里，屬地形變遷較為劇烈之區域。本段海岸每至颱風侵襲期間，受到巨浪侵襲，烏石港、蘭陽溪河口附近海岸變化加劇，海岸線侵蝕嚴重，雖有沿岸砂堤保護，仍然引起沿岸居民不安。 而為能掌握海岸變遷之特性，本局於94及95年針對此段海岸進行波、潮流、海氣象、漂沙與水深地形等大範圍之調查研究，已初步掌握宜蘭海岸之海、氣象特性。然而，距前次調查至今已經6年，期間受到歷次颱風侵襲影響，海岸環境及地形於近年來有變化加劇之情況；此外，依據水利署水利規劃試驗所擬訂之「海岸防護規劃基本資料觀測調查作業規範(草案)」建議，海岸相關現場調查在一般原則下，宜每5年進行一次，以做為相關工程規劃之依據，確定未來本段海岸環境復育具體方向。爰此，本局遂研提本計畫，擬分三年度執行，針對宜蘭縣頭城至蘇澳沙質海岸進行相關調查及研究，釐清本段海岸地形變遷機制，並依研究成果研提本海岸地形變遷之因應對策，以供本局未來進行海岸防護及環境復育營造之參考。本計畫工作包括海象及水深地形資料調查，並蒐集分析計畫區海岸相關基本資料，同時輔以數值模式進行海岸地形變遷之動力機制的分析及評估；最後，乃依據研析成果研提本段海岸整體之海岸防護及環境營造改善策略及規劃。

The main work (102) of this project includes the collection of background data, scope of the study between South Fang-Xi to North Ao-Zai-Jiao sandy in Yi-Lan area. The following tasks have been carried out for the second year period: (1) Data’s collection and analysis (2) Topographic survey and topography in Coastal water depth. (3) Drift littoral characteristics survey (4) Situ Investigation on Tide, Wave, Current and Sediment (5) Review protection and the impact of coastal structures (6) Proposed coastal protection measures and to improve the environment and create an initial idea (7)Comparative assessment of coastal protection improvement plan. The calendar of walrus data analysis : Between 1981 and 2013 the tide station in Su-Ao harbor, the highest tide is 1.44 meter, the maximum tidal range is 2.65 meter, tide average tidal range 1.78m. Between 2006 and 2013 the tide station in Wu-Shi harbor, the highest tide is 1.37 meter, the maximum tidal range is 2.56 meter, tide average tidal range 1.66m. At 2006 ~ 2009 , The ocean current data of Su-ao harbor, the ocean current main direction of N~NNE and SSW~SSE, the summer average velocity is 14~29 cm/sec , the winter is 14~45 cm/sec . the buoy of Su-Ao(1999-2013) summer waves direction of east-southeast, the average height of significant wave (H1/3) is 1.49 meter, the average significant wave period（T1/3）is 6.4 sec. When September 19, 2010 FANAPI Typhoon , the maximum wave height is 45.05 meter, period is 13.1 sec. almost the winter waves in the northeast , the average height of significant wave is2.01 meter, the average significant wave period is 6.6 sec. The topography of coastal illustrate: sea erosion and deposition terrain between the results of the second measurement, the overall situation showed erosion. The average erosion of elevation between -1 to 2 meters. The most serious erosion situation at Tau-Cheng the isobath waters between 0 to 5 meter and Gong-Guan 10~15 meter, Tau-Cheng average of erosion depth between -3~-4 meters. The Gong-Guan has erosion depth near the -5 meter. Near Lan-Yang rivulet and Wu-Shi harbor have accretions 3~4 meters. Lan-Yang rivulet has accretions caused by river sediment. The Wu-Shi harbor has accretions occurred in the north seawall. Between 1898 and 2001, the maximum parallel to the coastline retreat can be -200 meters .Between 1921 to 1978, The north Lan-Yang rivulet has accretion about 400 meter. The Tau-Cheng coastline retreat about -48 meters between 1978 to 1978 , the Da-Fu coastline retreat -31 meter. Between 2001 and 2006 , almost has erosions at Da-Fu, the other coastline has accretions. Another satellite image analysis of short-term shoreline change, the beach line move to seaward side between March and June, the coastline back on July to September. Monthly variance with the overall changes in the amount of statistic, the north Wai-Ao embankment most dramatic change, followed by most south Xin-Cheng rivulet. The coastal change at September 19, 2010 FANAPI Typhoon, has substantial erosion, the Coastline back between -33.0 meter and -11.3meter. Planning district field investigations tidal, wave and current: the tidal model belong mixed type of tide. The basis of moderate tide, high tide is 0.494 meter, average low tide is -1.187 meter, the average tidal range is 0.988 meter, the maximum tidal range is 2.074 meter. The results of the first survey (2012/04), the height of significant wave is 1.21 meters, period is 6.23 sec, the main wave direction NE to E. The main current direction parallel to the coastline, The underlying average velocity is 15.4 cm/sec, the main wave direction SE, the maximum velocity is 48.7 cm/sec, wave direction ESE, The surface layer velocity is 22.6 cm/sec, the main wave direction ESE, the maximum velocity is 74.4 cm/sec, wave direction SSE. The results of the second survey (2012/09), the height of significant wave is 1.52 meter, period is 7.54 sec, the main wave direction NE to E. the underlying currents velocity is 21.4 cm/sec, concentrated flow to ESE 、SE and WNW, the maximum velocity is 76.0 cm/sec, wave direction ESE ; The surface layer velocity is 31.4 cm/sec, concentrated flow to SE and NW, the maximum velocity is 121.6 cm/sec, wave direction SE. Planning District coastal sediment survey results: The first survey (2012/04), The D50 between 97.5 and 580.9μm, the high、low tide line’s D50 distributed between 228.9 and 498.9μm, The North Lan-Yang rivulet Sediment particle size distribution trends north increments, diminishing of South to south . The second (2012/09), the D50 distributed for the sea area between 7.8 and 285.9μm, the D50 distributed of the high and low tide line between 211.9 and 695.1μm;, the biggest sediment particle at She-Da north in Lan-Yang rivulet delivery to north and to south ,but south Lan-Yang rivulet delivery to south. During the project execution using the sand is catching to Survey Suspended drift twice, The results display direction of drift sea area perpendicular to the shoreline off point, another direction to parallel to the shoreline. The first survey (2012/04), in surf zone’s transfer rates between 10.12 and 32.56 cm3/min . The second survey (2012/09), in surf zone’s transfer rates between 12.97 and 109.93 cm3/min, out of surf zone’s transfer rates between 3.14 and 49.14 cm3/min. The run-up security assessment of coastal and seawall, 50-year return period for the design typhoon wave conditions, the case PL5 、PL13、PL14、PL19 and PL20 has flooding over may occur, The reason for this purpose five cases are located at the mouth , the high elevation has significantly lower than near the coast ,so easy lead to flooding over embankment situation. The comprehensive assessment of Tau-Cheng Protective effect, for the Tau-Cheng can be achieve maximum effectiveness of protection. Protection measures to improve the Zhuang-Wei village、Ji-Xin village and Gang-Bain ' s proposal: (1) Maintain the status quo. (2) Artificial beach nourishment: Regularly collect silt at Lan-Yang rivulet refilling the coastal erosion area. (3) Coastal planting: Though planting on sand fixation of engineering protections , complete effect to provide windbreaks clusters .(4) Geotextile tube works: Set in front of coastal planting increase the height can be wave energy to abatement and sand back.