蘭陽平原土地利用與地層下陷

Land Use and Land Subsidence in Lan-Yang Plain

盧光輝(Kwong Fai A. Lo) ； 陳癸月(Kuei-Yueh Chen)

《華岡農科學報》 17期 (2006/06) Pp. 37-48

https://doi.org/10.29985/HKJA.200606.0004

摘要

利用內政部艇建版1960、1975、1990及1997年4期的土地利用圖作比較，可看出蘭陽平原土地利用大致以水稻田爲土地利用的主體、聚落主要於道路沿線發展，而養殖漁業在1990年的土地利用圖中明顯增加，於平原的東部沿海地帶，北起頭城、南迄五結密集的分佈。本應爲顯著向外堆積的蘭陽平原海岸，各年代的地圖比對後發現，近三、四十年來不但沒有明顯的堆積出現，甚至出現後退的區段。克利金推估出的結果顯示，下陷量最大的區域以頭城和蘭陽溪出海口爲最，年下陷量均達20公分以上，套疊土地利用圖發現，此地恰好重疊在魚塭養殖面積最爲密集處。
地層下陷年速率與各年土地利用面積的相關性分析發現，道路、聚落與地層下陷相關性較高，呈正相關，其次爲魚塭，亦呈中度正相關；與水稻田面積則呈現負相關的趨勢。人爲土地利用改變確實會影響海岸變遷，由於近年來蓬勃發展的沿海地區養殖漁業、河川上游的整治工程等，導致地下水位下降、沿海地層嚴重下陷，並造成了蘭陽平原海岸受侵蝕後退的現況。

關鍵字

地層下陷 ； 海岸後退 ； 魚塭養殖 ； 地理統計 ； 地理資訊系統

並列摘要

Comparing land use maps obtained from the Ministry of Interior (the Economic and Development version) in the Lan-Yang Plain for 4 time periods (1960, 1975, 1990 and 1997), indicates that rice paddy is the mainstream use. Human habitat is concentrated and de eloped along major roads. Aquaculture farming increases significantly since 1990 along the eastern edge of the coastal plain, from Toucheng in the north to Wijie in the south. Land use comparison also points to the fact that the usual floodplain expansion is replaced by coastline recession in many sections due to sedimentation reduction in the last 30 to 40 years. The land subsidence estimation, based on kriging method, shows the annual subsidence rate exceeds 20 cm on the average. The most serious area is in the Toucheng and the estuary zone of the Lan-Yang Stream. This coincides perfectly with the densely concentrated aquaculture farming areas.
Correlation between annual rate of land subsidence and land used for road and human habitat are highly positive, followed by aquaculture farms. However, rice paddy is negatively related to land subsidence. This indicates that land use changes are indeed affecting the dynamic of the coastal plain. The rapid development of aquaculture farms in recent years along with upstream channel works have caused lowering of groundwater level, severe coastal land subsidence, and resulted in the coastal erosion and shoreline recession in the Lan-Yang Plain.

並列關鍵字

Land subsidence ； Coastline recession ； Aquaculture farming ； Geostatistics ； Geographic information systems