本研究針對台灣東部地區，以固定區域之方式求取降雨面積遞減因子(areal reduction factor)，進而建立降雨面積遞減曲線。首先，蒐集整理台灣東部地區 73個雨量測站之資料。接著將台灣東部地區以河系流域為依據劃分成六區，以期在將來水資源規劃應用上較為方便。然後針對近四十年(1970年至 2007年)來侵襲台灣東部地區之42 個歷史降雨事件資料，進行各個降雨延時之最大降雨量分析。再依據六個流域分區之小時及即時雨量資料，分別建立降雨延時為10；20；30；60 分鐘；以及 1；2；3；4；6；12；18；24；36 小時之降雨面積遞減曲線。在面積降雨之計算上，本研究採用克利金法(kriging)推求，以得到較為可靠之面積遞減因子。此外，由結果發現，本研究所建立之降雨面積遞減因子迴歸式之相關係數皆高於 0.95，表示用此函數型式計算降雨面積遞減因子相當合適。

The purpose of this study is to establish the areal reduction factors (ARF) of rainfall and ARF curves for eastern Taiwan. First, rainfall data of 73 gages located in southern Taiwan are collected. For the convenience of application in the future, the area of southern Taiwan is zoned into 6 areas. The 42 typhoon rainfall data with 40-year record length in eastern Taiwan are available and then the 10-, 20-, 30-, 60-min, 1-, 2-, 3-, 4-, 6-, 12-, 18-, 24- and 36-hr ARF curves are established. In order to obtain the precise ARF, the kriging method is used to estimate the areal rainfall. Finally, regression equations for ARF curves are proposed herein. It is found that the values of correlation coefficient are all higher than 0.95. These results demonstrate that this regression function can be successfully applied to determine the areal reduction factor.