台灣森林試驗集水區最大逕流量推算之初步研究

The Maxium Runoff Estimation of Experimental Forest Watersheds in Taiwan

黃正良(Jeen-Lian Hwong) ； 陳信雄(Hsin-Hsiung Chen)

《中華水土保持學報》 18卷1期 (1987/05) Pp. 36-48

https://doi.org/10.29417/JCSWC.198705_18(1).0004

摘要

本研究之目的在探究利用合理化公式來估算集水區之最大逕流量時，其逕流係數値及降雨強度間隔時間的決定方法。以林業試驗所蓮華池分所第3、4、5號三個小型試驗集水區以及畢祿溪第11、12號兩個試驗集水區的實測水文資料統計分析後作爲詮衡之依據。此外，於蓮華池地區選若干試區進行土壤物理性質實驗，並測定其土壤滲透率，以瞭解各種地況在不同降雨強度下其滲透率之變化與逕流的關係。類似畢祿溪試驗集水區，集水面積在100〜300 ha左右者，可採用最大一小時之降雨量推算其最大逕流量。逕流係數爲60〜75％。而集水區積小於10ha，地況類似蓮華池地區者宜採最大十分鐘雨量來推算其最大逕流量，其逕流係數在60〜70％之間。由蓮華池三個試驗集水區一場降雨量與逕流量之關係顯示，逕流率隨降雨量之增加而增高，兩者間呈指數關係。若依降雨量之大小分爲若干等級，則其逕流係數也會隨不同大小降雨之等級而異。蓮華池試驗區之各種林地0〜20公分層次的土壤其全孔隙率及含水潛能皆大於20〜40公分層次的土壤，而密度、比重則以0～20公分層次的土壤較小。該地區土壤滲透率的優劣次序爲天然濶葉林地、杉木造林地、砍伐跡地、舊步道。又在同一地況下土壤含水量飽和期之滲透量小於非飽和期。

並列摘要

This study was to evaluate runoff coefficients and time interval of rainfall intensity using ＂rational formula＂ to predict the peak discharge from small forested watersheds. Longterm hydrological records of discharge and rainfall at three small experimental watersheds (3-8ha) in Lien-Hua-Chi area and two larger experimental watersheds (100-300ha) in Pi-Lu-Chi area were analyzed. Physical characteristics as well as field infiltration capacity of soil in the Lien-Hua-Chi area were also investigated to evaluate differences among discharage characteristics of these sites. The results indicated that the suggested time interval of rainfall intensity using the rational formula is 60 munites, and the runoff coefficients ranged from 60 to 75% for the Pi-Lu-Chi experimental watersheds. For Lien-Hua-Chi experimental watersheds, the corresponding were 10 minutes and 60-70% respectively. Runoff ratio of a storm event increased exponentially with the rainfall amount for all studied watersheds. In Lien-Hua-Chi area, soil moisture holding capacity and soil porosity are greater at the top 20cm soil then that at the 20-40cm depth. Bulk density and specific gravity, however, increased with soil depth. Field infiltration rates of various ground conditions decreased in the following order: natural hardwood forest, China-fir plantation, clearcut, old trail.