Fixed Electromagnetic Wave Surface Velocimetry (Fixed EWSV) has been started to be used to measure flood discharge in the mountain stream, since it has various advantages such that it works well to continuously measure stream discharge even in the night time as well as very strong weather. On the contrary, the Fixed EWSV only measures single point surface velocity, thus it does not consider varying feature of the transverse velocity profile in the given stream cross-section. In addition, a conventional value of 0.85 was generally used as the ratio for converting the measured surface velocity into the depth-averaged velocity. These aspects could bring in error for accurately measuring the stream discharge. The capacity of the EWSV for capturing rapid flow velocity was also not properly validated. This study aims at conducting error analysis of using the EWSV by: 1) measuring transverse velocity at multiple points along the cross-section to assess an error driven by the single point measurement; 2) figuring out ratio between surface velocity and the depth-averaged velocity based on the concurrent ADCP measurements; 3) validating the capacity of the EWSV for capturing rapid flow velocity. As results, the velocity measured near the center by the fixed EWSV overestimated about 15% of the cross-sectional mean velocity. The converting ratio from the surface velocity to the depth-averaged velocity was 0.8 rather than 0.85 of a conventional ratio. Finally, the EWSV revealed unstable velocity output when the flow velocity was higher than 2 m/s.

화원 지점의 홍수시 유량은 수위가 상승할 때와 하강할 때 동일한 수위에 대해 많은 차이를 나타내고, 이와 같이 이력효과의 크기가 클 경우에는 많은 오차가 발생할 수 있다. 유량 환산 오차를 줄이기 위해 낙동강 본류 화원 수위관측소 지점에 대한 고리모양 수위-유량 관계곡선을 작성하였다. 하천유량과 단순 환산된 유량의 편차를 계산하기 위해 부정류 모의 사례로부터 (수위, 유량) 자료쌍을 획득하여 단순 수위-유량 관계곡선식을 작성하였다. 이 관계에서 이탈하는

낙동강의 화원-교령교-현풍 수위관측소 구간에 대하여 수리학적 하도추적을 통하여 조도계수를 추정하였다. 세 관측소의 연속 수위자료와 하천 종횡단 측량자료만이 이에 사용되었다. 하도추적에 의해 계산된 유량자료로부터 수위-유량 관계식을 작성하였으며 이는 기존의 수위-유량 관계식보다 나은 결과를 보였다. 수위측정 오차가 유량계산에 미치는 영향에 대하여 분석하였으며, 측방유입류를 억제할 수 있도록 하도길이를 제한하는 방법도 제시하였다.

수리학적 하도추적으로부터 하천유량을 간접추정하였다. 짧은 하천구간의 세 지점 연속수위자료와 하천 단면 자료만을 사용하여 조도계수 추정b과 하천유량 계산이 가능하였다. 유량의 간접추정 과정에서, 상류-하류 경계조건을 수위-수위 조건으로 사용하였다. 미국 미시시피 강의 상류 구간 자료가 사용되었고 수리학적 하도추적에는 DWO-PER (operational dynamic wave model)를 이용하였다. DWOPER 모형에서 수정 Newton-Raphson

Derivation of stage-discharge relationship and characteristics for Yangsan river is presented in this paper. This research has been conducted as the second one after the first trial in 1997. The determination of discharge at a Yangsan river gauging was best made by measuring the flow velocities with a current meter and rod float. The rating curve obtained through 52 stage-discharge measurements on Yangsan river basin in 1999 is represented by Q=15.3540-140.6076H+182.44372H2, which is discovered to be most excellent among other curves in reliability analysis. The observed stage-discharge data for Yangsan river was tested by HEC-RAS program, and reproduction of discharge by the induced curve was investigated and compared with the computational results. The rating curve of Yangsan river shows characteristics of Yangsan river more accurately compared with those separated in terms of water levels.