多源遙測影像於宜蘭海岸濱線變遷偵測之應用

Abstract

本研究以不同時期之遙測影像進行宜蘭海岸濱線變遷偵測，影像來源包含1947 年之舊航照影像、1971 年的美國Corona 衛星影像、2003 年的SPOT-5 衛星影像及2009 年農林航空測量所以Z/IDMC（Digital Mapping Camera）航空數位相機所拍攝之高解像力航照影像。由於影像獲取的時間與感測器皆有所差異，故本研究透過不同的方式處理資料，將影像進行地理對位，然後利用地理資訊系統軟體數化濱線及沙灘（丘），並進行套疊分析，以觀察不同時期濱線變遷之情形。研究結果顯示，自1947 年至2009 年，濱線指標如水線與植物線都有向海洋推移的趨勢，由於突堤效應，濱線在烏石港北方因沉積增加而有往外擴張的趨勢，在其南方則因加速沖蝕而有後退的現象。在1947 年至1971 年期間，宜蘭海岸沙灘（丘）堆積的現象較明顯，在1971 年至2009 年期間則有明顯的侵蝕現象。利用多時期之遙測影像，並結合GIS 之空間分析功能，確可有效掌握濱線與沙灘（丘）的歷史變化概況。

This study used multi-source remote sensing images to detect shoreline changes along the Yilan coast. Various types of remote sensing images were used in this study, including old aerial images taken in 1947, Corona satellite images acquired in 1971, SPOT-5 satellite images acquired in 2003, and high-resolution aerial images taken in 2009 by the Aerial Survey Office using Z/I DMC (Digital Mapping Camera). Because these images were taken in different time using different sensors, different procedures were applied to process the data and georeference the images to a common coordinate system. GIS (Geographic information Systems) software was used to digitize shoreline and the beach area, then overlay analysis was applied to find the shoreline changes in different time periods. The results show that, between 1947 and 2009, shoreline indicators (both water line and vegetation line) moved toward the sea. Due to groin effect, the shoreline at the north side of Wushih Harbor moved outward as sediment increased, and the shoreline retreated at the south side as erosion accelerated. The beach areas of Yilan increased between 1947 and 1971; in contrast, more erosion was observed between 1971 and 2009. By using multitemporal remote sensing images and spatial analysis functionalities of GIS, the historical changes of shoreline and beach area can be detected effectively.