苗栗三義火炎山地區的沖蝕特性之研究

Characteristics of the Erosion in Hoyenshan Area, Miaoli

林俊全(Jiun-Chuan Lin) ； 鄭遠昌(Yuan-Chang Cheng) ； 任家弘(Chia-Horn Jen)

《中華水土保持學報》 38卷3期 (2007/09) Pp. 275-285

https://doi.org/10.29417/JCSWC.200709_38(3).0006

摘要

火炎山自然保留區爲現有的19個自然保留區之一，其特徵爲蝕溝發達、地表沖刷作用強烈，邊坡垂直聳立礫石惡地地形。本研究將集水區的源頭、河道、沖積扇三個區域變動的趨勢與變化量，加以說明其特色。
研究結果顯示，火炎山邊坡後退的形式有兩種，一種爲平行後退，多出現在搬運能力強的地方；另一種爲減坡後退，多發生在順向坡的邊坡。民國80年～91年的資料顯示，10 年間平均的後退速率分別爲平行後退邊坡每年2.5-3公尺（以3號集水區的邊坡計算）、減坡後退邊坡每年1.5公尺（以4號集水區的邊坡計算）。
在集水區源頭，侵蝕地貌的範圍不斷擴大，裸露地的後退速率以3號集水區最快，達每年3公尺，此結果比兩種邊坡後退的速率稍快。民國75年～91年間，以民國91年的變遷幅度最大，主要的原因是受到民國90年的桃芝颱風及納莉颱風影響。

關鍵字

火炎山礫岩 ； 平行後退 ； 邊坡後退 ； 地形變遷 ； 蝕溝 ； 颱風 ； 豪雨 ； 沖蝕作用

並列摘要

The Hoyenshan area, famous for its rugged gullies, was designated a nature reserve in 1986. This study quantifies the morphological changes of the conglomerate rock area over the last 20 years, by applying photogrammetric methods to a series of aerial photography acquired over a 20 year period. This enabled change detection to be conducted for the spatial extent and position of key geomorphological features. The results demonstrate two slope retreat processes: (1) parallel retreat, where the slope angle remains constant; this normally occurs in areas of high erosion; (2) slope retreat, where the slope angle reduces and this is often associated with an extension of the toe; this normally occurs on dip slopes.
Between 1991 and 2002, 2.5m of average parallel retreat at No. 3 catchment and 1.5m of average slope retreat at No. 4 catchment were observed.
At the headwater areas, parallel retreat of the slope could be as high as 3m and for catchment No. 3 this is associated with significant deposition of slope forming material into the gullies. The topographic elevation of the gully floors do not appear to change and this suggests dynamic equilibrium.
The effects of typhoon Toraji and Nari in year 2001 produced significant morphological changes, and these are clearly reflected in catchments No. 3 and 4.

並列關鍵字

hoyenshan conglomerate rock ； parallel retreat ； slope retreat ； morphological change ； gullies ； typhoon ； heavy rainfall ； erosional processes