水位流量率定解析方法及其不確定性

Abstract

本文旨在利用明渠水力履性圖(Hydraulic performance graph)概念推求理論(定常河段近似正常流)率定曲線，以USGS傳統之坡度參數流量率定方法為基礎，建立水位－落差－流量關係曲線。為驗證其實用性將本文提出之程序實際應用於基隆河與高屏溪並進行不確定性分析，結果顯示河道幾何條件及糙率係數等參數都會影響河段之水力履性圖、流量與落差關係指數與關聯性，進而造成水位-落差-流量關係的變化。本文提出之率定方法因係根據實際水理計算而得，在應用上不必以試誤法對照修正可降低其不確定性，而實測水位流量資料僅在提供已足夠率定關係之檢定驗證，能節省大量時間、人力，且無高流量偏離與可信度偏低問題。

This thesis presents an analytical method for establishing stage-fall-discharge rating using hydraulic performance graph (HPG). The theoretical rating (steady reachwise approximated normal flow) curves derived from the HPG are used as the basis to establish the functional relation of stage, fall and discharge through regression analysis following the USGS procedure. In doing so, the conventional trial-and-error process can be avoided and the associated uncertainties involved may be reduced. For illustration, the proposed analytical method is applied to establish stage-fall-discharge relations for the Keelung River and Kaoping River in Taiwan for examining its accuracy and applicability in natural rivers. Based on the data extracted from the HPG for the Keelung River and the Kaoping River, one can establish a stage-fall-discharge relation that is more accurate than the one by the conventionally used relation; the associated uncertainties can be analyzed. The uncertainty analysis shows that the channel geometry and channel bed roughness should be the significant factors to affect the functional relation of stage, fall, and discharge. Furthermore, the discharges obtained from the proposed rating method are verified through backwater analysis for measured high water level events. The results indicate that the analytical stage-fall-discharge rating method is capable of circumventing the shortcomings of those based on single-station data and, consequently, enhancing the reliability of flood estimation and forecasting.