圖書典藏及影音數位平台

大坪溪位於新竹縣境內，為中央管河川中港溪支流峨眉溪上游主要水路。本溪發源於新竹與苗栗兩縣交界之鵝工髻山，流經峨眉與北埔兩鄉，本溪治理範圍自下河背橋至深壢橋止，全長12.94公里，下河背橋以上之流域面積為59.50平方公里，河道坡度約1/44。 本溪自民國87年公告迄今已歷時11載，期間歷經民國88年921大地震及數十次颱洪，河道地形及周邊環境均有變化，為配合河道地形環境變化及社會發展需求，擬分2年(民國99年至100年)辦理中港溪支流大坪溪治理規劃檢討及基本計畫。其中，第1年委辦「中港溪支流大坪溪治理規劃檢討」、第2年自辦「中港溪支流大坪溪治理基本計畫」。

The original improvement plan the Daping River war formalized in 1998. In the 12 years since, the river has experienced the 921 earth quake in 1999 and numerous floods cased by typhoons. As a result considerable changes the taken place on river topography and the surrounding environment. To accommodate changes and the surrounding environment as well as needs for society development, a review of the improvement plan was initiated. On the bases of topography, hydrology, and social and environmental data in the drainage basin as well as causer of pant flooding, this study is to make an overall review and analysis of Daping River. This shall be need as references for subsequent river management and future basin-wide improvement planning. The Pearson Type III distribution of 48 hr storm event was used to determine rainfall pattern for hydrologic analysis, and modified triangular unit hydrograph, dimension less unit hydrograph and HEC-HMS dynamic wave methods were used to determine peak discharge for various flood recurrence intervals. The results dynamic wave method were close to the 「Xinchu Daping River Improvement Planning Report」published in 1998. Therefore, it was recommended that the peak discharges presented in the 1998 reports be remained. However, the 1998 report did not establish control station at confluence with Puwei Creek, and the drainage area of Dahu Creek was too small. Thus, it is suggested that at the outlet of both Puwei and Dahu Creek, the results of this study shall be used. Comparisons were made of flood stages of this study with those presented in 1998 results. In the 1998 study the analysis was made with the planned bed profile, as oppose to the actual profile used in this study. It was found that downstream from the No.1 debris dam(Cross Section 45.3), between the two studies, the maximum stage level varied with locations the difference in river-bed levels. Upstream from the No.1 debris dam, however, the 1998 results were higher than the present study. It was found that over the years, the river bed of Daping River exhibited erosion in the upstream reach and accretion in the middle and downstream reaches, but the level of changes is small. It is recommended that results of the present study be used as the planned stage level and a free board of 1m be added to establish the crest of dikes. Upstream reach of Daping River is a braid channel, but the stream is relatively stable. For flood control, it is suggested 2,193m of dikes be constructed or rebuilt and 1,250m of dikes be raised or strengthened.