Technical Studies


Study on Evaluation of Rating Curve for Kaoping River

The purpose of this study is to examine the feasibility of using the hydraulic performance graph (HPG) to construct the rating curve for Kaoping River. So far the derivation for the theoretical rating curve has been completed. The one-and two- dimensional water flow models which might be used to provide the flow pattern date for HPG have also been validated through the application to some hypothetical cases. In order to examine the applicability of the HPG to Kaoping River, the Lilin station has been selected as a study target. On the basis of the river cross section investigated a roughly estimated rating curve has been established. However, from the preliminary results obtained one can find that the detailed three-dimensional flow patterns through the bridge pier and the hydraulic structure neighboring to the gage station has to be computed to derive the more accurate rating curve by using the HPG concept. The methodology developed for Lilin station will be applied to the other stations It is expected that one can save a tremendous amount of expanses by using HGP to derive rating curve instead of the conventional technique.

A method for determining the flow carrying capacity of a channel system, capable of accounting for the interacting backwater effect among channel reaches, is presented here. The method makes use of hydraulic performance graphs –a new tool for dealing with open-channel-flow problems. The hydraulic performance graph summarizes all the backwater profile information for a channel reach. As an illustration, the method is applied to evaluate the rating curve of a portion of Kaoping River in the south of Taiwan. The objective of this paper is to report how to use this method for determination of the rating curve of a single channel reach, compounded cross section with floodplain, as in the Taiwan rivers, natural or human-made including streams, lateral flow, canals, bridges, fixed bed, weirs, or sewers, and of a number of reaches together as a system. The N-line is the locus of normal flow profiles is investigated and defined here as the curve line different from the originally defined by HPG. This method after modified is submitted and suitable to a new approach for investigating the rating curve of rivers in Taiwan.