蘭陽平原土地利用與海岸變遷

Land Use and Coastal Changes in Lan-Yang Plain

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

《華岡農科學報》 13期 (2004/06) Pp. 1-14

https://doi.org/10.29985/HKJA.200406.0001

摘要

利用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為土地利用的主體、聚落主要於道路沿線發展，而養殖漁業在1990年的土地利用途中明顯增加，於平原的東部沿海地帶，北起頭城、南迄五結密集的分佈。本應為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。人為土地利用改變，確實會影響海岸變遷，由於70年代起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、沿海地層嚴重下陷以及河川補注地下水量增加、逕流量減少，加上治山防洪計畫，在上游設置防砂壩、下游興建堤防圍堵、設堰攔阻取水，使得輸砂能力明顯減弱，致海岸砂源減少，於是造成了蘭陽平原海岸今日受侵蝕後退的現況。

關鍵字

輸砂量 ； 地層下陷 ； 海岸後退 ； 魚塭養殖 ； 河川整治

並列摘要

Comparing land uses 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 developed along major roads. Aquaculture farming increases significantly since 1990 along the eastern edge of the coastal plain, from Toucheng in the north to Wujie 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. This indicates that land use changes are indeed affecting the dynamic of the coastal plain. The rapid development of aquaculture farms in the 70's along with upstream channel works have caused lowering of groundwater level, severe coastal land subsidence, increased groundwater replenishment in creeks and streams, and surface runoff reduction. In addition, the construction of check dams, levee protection, and retention dams in the watershed protection and flood prevention program often weakens the sediment delivery ability and resulted in the current coastal erosion and shoreline recession in the Lan-Yang Plain.

並列關鍵字

Sediment yield ； Land subsidence ； Coastline recession ； Aquaculture farming ； Channel works