礫石地逕流係數與入滲現象之研究

黃昭蓉(Chao-Jung Huang)

指導教授 ： 吳嘉俊

國立屏東科技大學/工學院/水土保持系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00067

摘要

本研究利用坡長30m、平均坡度20°(36%)、寬度4m、地表礫石平均敷蓋率53%、土體內礫石體積平均含量22%的四個試驗小區，進行現地試驗，以探討礫石地之逕流係數，並透過土壤水分張力監測及單環入滲試驗，以瞭解礫石地之水分入滲現象，及土體礫石含量對水分入滲及飽和水力傳導度的影響。由試驗探討得以下結論：
本研究發現，影響礫石地逕流係數之最重要因子為(I30)max，三日臨前降雨總量次之，影響最小的因子為雨型。於本研究之試驗條件下，礫石地之逕流係數期望值範圍為0.19 ~ 0.49。當(I30)max大於45mm/hr時，礫石地之逕流係數期望值將大於0.47；當三日臨前降雨總量大於47mm時，逕流係數期望值將大於0.5；而各雨型之逕流係數期望值分別為均佈降雨0.30、前端降雨0.31、後端降雨0.33，對礫石地之逕流係數影響不大。
由土壤水分張力計監測結果顯示，越接近地表之土層，其對於土壤水分之飽和及乾燥反應時間皆較快，平均約3日內即可明顯看出乾燥反應。由單環入滲計地表下20cm內之入滲試驗結果顯示，當土體內含有19%至63%不等之礫石時，飽和水力傳導度可高達16.90至98.88cm/hr，而無論礫石含量多寡，土壤水分之入滲率於入滲歷程中都會有明顯或微小的遽增現象。

關鍵字

礫石地 ； 逕流係數 ； 土壤水分張力 ； 飽和水力傳導度

並列摘要

Field observations were conducted on 4 runoff plots at National Pingtung University of Science and Technology. Each plot measured 30m along the slope, 4m across the slope, with average gradient of 36%. The average volumetric gravel content was found to be 22%, and the average surface cover by exposed gravel was around 53%. Matrix suction potential as well as in-situ saturated hydraulic conductivity were monitored and measured using tensiometers and single-ring infiltrometer. The objectives of this study are two folds: one is to obtain the runoff coefficient for gravel-rich soil, and the other is to understand how gravel influences the infiltration. Conclusions can be outlined as follows:
Results from this study indicate that the maximum 30-min rainfall intensity (I30)max is the most influential factor to runoff coefficient, followed by 3-day antecedent precipitation, and storm types. The expected runoff coefficient under this study’s conditions ranges between 0.19 and 0.49. When (I30)max is greater than 45mm/hr, runoff coefficient from gravel-rich soil is expected to reach 0.47. When 3-day antecedent precipitation exceeds 47mm, the runoff coefficient may reach 0.5. On the other hand, storm type does not affect the runoff coefficient.
From suction potential measurements we found that soil situated close to ground surface can quickly reflect the wetting and drying processes. Distinct drop in suction potential can be found 20cm below the ground surface 3days after the storm. The saturated hydraulic conductivity was found to be high in the range of 16.9 to 98.88cm/hr when soil is packed with 19 to 63% of gravel by volume. Regardless the volumetric content of gravel in soil, spikes that represents sudden increases can be found repeatedly on infiltration rates during the infiltration process.

並列關鍵字

Gravel-rich soil ； Runoff coefficient ； Soil moisture tension ； Saturated hydraulic conductivity

參考文獻

立中央大學土木工程研究所，桃園。

13.吳輝龍、張文詔、黃俊德，1995，「坡地檳榔園試區水土流失量第一年成果初步探討」，中華水土保持學報，第26卷，第3期，第197-209頁。

36.鄭鑑鏘、謝昭賢，1979，「強度放牧對盤固草地水土流失影響試驗」，中華水土保持學報，第10卷，第2期，第67-73頁。

40.鄧屬予，1996，「台灣卵礫石層的地質背景」，地工技術，No.55，第5-24頁。

1.水土保持技術規範，2005，行政院農業委員會水土保持局編製，南投