花東兩縣土石流現場調查與分析

Field Investigation of Debris Flow in Hualien and Taitung Counties

謝正倫(Cheng-Lun Shieh) ； 江志浩(Jyh-Haw Jiang) ； 陳禮仁(Li-Jen Chen)

《中華水土保持學報》 23卷2期 (1992/11) Pp. 109-122

https://doi.org/10.29417/JCSWC.199211_23(2).0010

摘要

花蓮與台東是本省土石流災害頻繁之地區，本文透過現場調查與資料分析，研究本區土石流之特性。本文首先對兩縣內之土石流危險溪流進行調查，經確認兩縣共計295條溪流曾有土石流之發生經驗。此外針對上述危險溪流進行地形特性分析，得出其溪流坡度大都分佈於10°～25°間(佔87%)，而集水面積則以10公頃～120公頃間最多〈估62%)，長度則分佈於500公尺～2000公尺間(佔81%)。其次針對降雨與土石流發生之關係進行分析，可知曾誘發本區土石流發生之暴雨中其最大時雨量以65mm／hr為代表，而以27mm／hr為下限。兩者皆小於花蓮縣之5年頻率降雨。最後計對土石流之土砂流出量與集水面積之關係進行分析，發現花蓮地區單位流域面積之土砂流出量大於日本全國之平均標準。同時推估該區土石流流動時對河床之侵蝕厚度約在0.5m～3.5m間，此項數據與日本全國調查資料相近。

關鍵字

土石流 ； 現場調查

並列摘要

Hualien and Taitung are the two counties in Taiwan where damages caused by the debris flow take place most frequently. This paper presents the study of the debris flow in these areas through both field investigation and data analysis. Field investigation on streams in these counties with high potentials for the debris flow to take place is conducted first. As a result, a total of 295 streams are found to have experienced the debris flow in the past. Analyzing the geographical characteristics of these streams, it is interesting to find that most of the slopes (about percent) are between 10 to 25 degrees, about 62 percent of the streams have watershed area between 10 to 120 hectares, and nearly 81 percent of the screams have the length between 500 to 2000 meters. the relationship between the prceipitation and the occurrence of the debris flow is examined next, the records show that the amounts of hourly precipitation range from 27 to 65 mm. This range lays below the Hualien county's precipitation record with return period of 5 years. Finally, the quantity of the debris is linked to the size of watershed area, and it shows that the amount of debris per unit watershed area in Hualien is greater than the erosion depths on the stream bed are estimated to be 0.5 to 3.5 meters, which are very close to the results from similar investigations conducted in Japan.

並列關鍵字

Debris Flow ； Field investigation