東部蘭陽地區土石流現場調查與分析

Field Investigation and Analysis of Debris Flow in Lan-Young East Area

10.29417/JCSWC.199606_27(2).0006

張東炯(Tung-Chueng Chang)；謝正倫(Chjeng-Lun Shieh)

土石流 ； 現場調査 ； Debris Flow ； Field Investigation

中華水土保持學報

27卷2期（1996 / 06 / 01）

139 - 150

繁體中文

本文之目的係透過現場調査與分析，研究本省東部蘭陽地區包括宜蘭縣、花蓮縣及臺東縣三個地區之土石流現況及特性。首先對此三縣市之土石流危險溪流進行調査，經確認三縣市內共計335條曾有土石流發生過。而危險溪流處之地形特性經分析後發現，溪流坡度大部份分佈於10°〜25°之間，佔總數之84％，溪流長度集中於500〜2,000公尺之間，佔總數之70％，另外集水面稽則以10〜150公頃之間佔總數之63％。其次針對降雨與土石流發生間之關係進行分析，得知曾誘發本區土石流發生之暴雨中，其最大時雨量宜蘭地區以24 mm / hr爲代表值，而以21 mm / hr爲其下限值，花東地區以65 mm / hr爲代表值，以27 mm / hr爲下限値，兩者皆小於兩縣之5年頻率降雨。最後係將土石流之土砂流出量與集水面積之關係進行分析，發現宜蘭縣、花蓮縣地區單位流域面積之土砂流出量均較日本全國之平均標準值爲高。同時推估該區土石流在溪床上通過時所造成之侵蝕深度約在0.5〜3.0 m之間。

This paper presents the study of the debris flow in the Lan-Young East Area including Han, Hualien and Taitung countries through both field investigation and analysis. Field investigation on streams with high potentials for the debris flow to happen in these countries is conducted first. As a result, a total of 335 streams are found to have experienced of the debris flow in the past. Analyzing the geographical characteristics of these streams, it is interesting to find that most of the slops about 84 percent are between 10 to degree, almost 70 percent of the streams have the length between 10 to 150 hectares. The relationship between the precipitation range from 21 to 24 mm in Ilan county and 27 to 65 mm in Hualien and Taitung counties. These range lays below the Ilan and Hualien Counties' precipitation record with return period of 5 years. Finally, the quantity of the debris is connected to the size of watershed area. It shows that the amount of debris per unit watershed area in those area is higher than the Japan, the erosion depths on the stream bed are estimated to be 0.5 to 3.0 m.