台灣小森林集水區暴雨流量特性之研究

The Stormflow Characteristics of Two Small Forest Watersheds in Taiwan

胡蘇澄(Su-cherng Hu)

《中華水土保持學報》 18卷1期 (1987/05) Pp. 49-58

https://doi.org/10.29417/JCSWC.198705_18(1).0005

摘要

本研究爲探討本省高山保安林調節洪水功能之先期工作，乃以暴雨事件爲基礎，研究闡釋畢祿溪試驗集水區暴雨流量之特性。本研究地區畢祿溪試驗集水區包括第11號及12號兩個小集水區，面積分別爲144及238公頃，位於大甲溪上游保安林區；年平均雨量約2,400 mm，年平均氣溫約12.5℃；平均坡度分別爲82％及74％，板岩地質較脆弱而不穩定；土壤屬礫片坋質森林土壤，排水良好，滲透性佳；森林由針闊葉林混合組成，覆蓋良好。經挑選兩集水區1982年至1984年三年間第11號第54組第12號52組暴雨事件之流量歷線爲基本數據資料，採用Hewlett及Hibbert建立之0.00547 l/s/ha/hr之分離斜率分離暴雨期之溪流量爲暴雨流量與延遲流量，並計算降雨量、臨前基流量、暴雨流量延時、尖峯流量及尖峯到達時間等暴雨流量參數值，並分析水文反應突現性（Flashiness）、尖峯流量大小及尖峯逕流係數及臨前基流量對暴雨與流量關係之影響；再以廻歸方程式探討兩集水區暴雨流量參數之相關性。研究所得之主要結果列述如下：1.兩集水區暴雨流量與雨量關係統計上甚爲密切，似可以廻歸式由雨量推估暴雨流量。2.每次暴雨之水文反應均不相同，第11號集水區界於0.1〜65％（平均11％），第12號界於0.9〜86.5％（平均15％）；兩集水區之流量歷線甚爲接近，上升迅速，尖峯到達時間短暫，通常在流量歷線上升後十五小時以內；每逢連續降雨則出現多峯；退水曲線隨降雨終止而迅速衰減；證明上游集水區地勢陡峻土層淺薄，對於滯蓄暴雨的潛能有其限度，尤其在發生連續降雨後，集水區土壤水分趨近飽和或田間容水量，再遇降雨，則大部分水流很快成爲暴雨流量而顯示集水區水文反應高度的突現性。3.尖峯流量大於5 l/s/ha者第11號集水區佔18％，第12號集水區佔14％，差異可能與集水區面積有關。再以最大小時雨量推算尖峯逕流係數，第11號集水區在0.118〜0.954之間，第12號在0.147〜0.375之間。4.臨前基流量在兩試驗集水區未能顯示集水區平均蓄水狀態。5.兩集水區主要暴雨流出事件（Qu ＞ 25mm）暴雨流出特性之統計分析結果顯示兩集水區水文特性關係甚顯著。

關鍵字

森林水文 ； 暴雨流量之水文 ； 降雨逕流關係 ； 暴雨流量歷線分析 ； 水文反應 ； 台灣小集水區研究

並列摘要

The purpose of this study is to improve the understanding of rainfall-stormflow relationships of mountain watersheds in Taiwan for both watershed management and scientific purposes. Rainfall and streamflow data on storm event basis were collected and analysed as part of the calibration of two small high elevation forest watersheds. Pi-lu-chi No.11 (WS-11) and Pi-lu-chi No.12 (WS-12) located in protection forests, upstream of Tachia River Basin and near Lishan in central Taiwan. The stormflow characteristics were summarized of these two 2 to 3-order watersheds, 144 hectares and 238 hectares, respectively, during the period of 1982 to 1984. A total of 54 storm events on WS-11 and 52 ones on WS-12 and their corresponding stormflows were studied based on storm hydrograph analysis. The slope of 0.00547 l/s/ha/hr proposed by Hewlett and Hibbert was used for hydrograph separation. Then stormflow or quickflow amount (Qu), delayed flow (Qd), rainfall of storm (Pg), antecedent baseflow (qi), duration of stormflow (Td), peak flow (Qp), time to peak (Tp), recession time (Trc), proportion of runoff to rainfall (Qu/Pg) or hydrologic response (R-index), peakflow runoff coefficient (Cp) in rational method for major events with quickflow greater than 25 mm, constants of six recession curves were calculated. Regression of quickflow on rainfall for both watersheds was made. The statistical role of antecedent baseflow in the rainfall-runoff relationship was tested. Regression equations were derived for storm flow parameters, including qi, Qp, Tp, Qu, Td, Trc and Tre/Tp, of WS-11's and WS-12's to determine whether sufficient correlations exist between the two watersheds. A highly significant relationships between the stormflow and rainfall may be used for prediction purpose. Stormflow amount accounted for 11 percent and 15 percent of the storm rainfall on the average, varying greatly from 0.1 to 65% and 0.9 to 86.5%, for WS-11 and WS-12, respectively. Shapes of stormflow hydrographs of WS-11 and WS-12 were similar: stormflow peaks mostly occurred in 15 hours after the start of a rainfall event; multiple peaks shown when storms occurred consecutively; recession curves depleted quickly following the end of storms. These indicate an overall flashy nature of stormflows from both watersheds with steep slopes and shallow soils. Instaneous peak flows of both watersheds varied considerably with individual storms. Peak flows greater than 5 I/s/ha accounted for 18% and 14% of total peak flow measurements for WS-11 and WS-12, respectively. Based on maximum hourly rainfall, the coefficients of peak flows for WS-11 and WS-12 varied from 0.118 to 0.954 and 0.147 to 0,375, respectively. Antecedent baseflow rate was statistically tested and rejected as a good index of watershed soil water storage prior to the storm hydrograph rise. Therefore, field measurement of soil water contents is required for improvement of the rainfall- stormflow prediction. The regression analysis of stormflow hydrograph parameters of nine major storms (Qu ＞ 25mm) between WS-11 and WS-12 derived the following regression equations, indicating that the two watersheds are highly related hydrologically.

並列關鍵字

forest hydrology ； stormflow hydrology ； rainfalI-stormflow relationship ； storm hydrograph analysis ； hydrological response ； Taiwan's small watershed studies