Rating Curve Modification at Low Discharges Using Physical Model Tests

Shun-Chung Tsung,Hau-Wei Wang,Yun-Ling Chen,Jihn-Sung Lai

doi:10.4236/wjet.2015.32005

Abstract

Hydraulic structure is designed based on hydraulic theories or guidelines. To ensure performance, physical model tests are often used at high discharges. However, high discharge in river is rare. Physical model tests at high discharges will probably lead biased hydrological relationship. To improve hydrological relationship at low discharges, in this study, we considered the diversion rating curve of the Yuanshanzi Diversion Work. The 1/100-scaled physical model tests at low and high discharges (90 - 1620 m3/s) were performed and coupled the diversion discharges of 5 flood events (2009-2010) in field. The official diversion rating curve was built only based on physical model tests at high discharges (837 - 1620 m3/s). The results of physical model tests in this study suggested the official diversion rating curve should be modified considering all tests. The modifications showed the official diversion rating curve was over-estimated. A complete series of physical model tests and considering field situations, in this study, indicated expanded physical model tests and constantly field measurements were therefore necessary for hydraulic structure, which provided information to modify used hydrological relationship to fit real situations.

Highlights

Hydraulic structures are always designed based on hydraulic theories or certain guidelines [1] [2] and engineers often check design requirements using physical model tests [3] [4]
The present official diversion rating curve, Equation (1), to estimate diversion discharge was built based on physical model tests at high inflow discharges (Qi > 837 m3/s)
This study focused on diversion discharge of the Yuanshanzi Diversion Work

Summary

Introduction

Hydraulic structures are always designed based on hydraulic theories or certain guidelines [1] [2] and engineers often check design requirements using physical model tests [3] [4]. Engineers often consider high design discharges, such as extreme flow conditions, for physical model tests to guarantee proposed operation of hydraulic structure and fit design requirements. Flow patterns around the Yuanshanzi Diversion Work are complicated, because the work with an asymmetric stilling pond locates at curved reach of the Keelung River. The water level site for present official diversion rating curve is LS4 that locates at left bank and in front of the diversion weir [7]. The present official diversion rating curve was established based on measurement data of previous physical model tests [4]. Where Qd is diversion discharge [m3/s]; L is length of the diversion weir (80 m); H is measured water level at LS4 [m]

Physical Model Tests

Modification of Diversion Discharge

Verification of Modified Diversion Rating Curve

Conclusions