본 연구에서는 유입유사에 따른 저수지 내 퇴사 분포를 정량적으로 분석하고 효율적인 저수지 관리를 위하여 2차원 수리 유동 모형인 RMA-2와 유사이송 모형 SED2D를 사용하여 76년 장기 퇴사분포를 예측하였다. 모형의 입력 자료인 수위-유량자료는 한국수자원공사에서 관측한 실시간 자료를 활용하였으며, 유사량 자료는 한국수자원공사에서 개발한 K-DRUM 모형을 사용하여 대상영역의 유사량 값을 산정하여 적용하였다. 또한 갈수기시 저수지내 단면 코어채취를 수행하여 퇴적깊이를 모형 결과와 비교하였다. 검증결과 저수지 내 퇴적깊이는 비교적 실측값과 유사하게 나타났다. 장기 퇴사분포예측은 2012년 실측한 지형자료를 시작단면으로 하여 2088년까지 76년간 모의를 수행하였다. 모의결과 합천댐 상류구간에서 1.63~1.26m, 하류구간에서 1.45~0.007m의 퇴적층이 형성되었으며, 전체적으로 침식보다 퇴적이 우세한 결과를 보였다.

An objective of this study is as follows: 1) performing sensitivity analysis and parameter estimation of RMA2 and RMA4 models for the West-Nakdong River, 2) drawing up alternatives of gates-operation for water-quality enhancement, and 3) quantitative evaluation of methodology of 'flow-restoration by gates-operation' among 'Comprehensive Plan Improving Water-Quality in the West-Nakdong River(WNR)' with the target water-quality(BOD at Nakbon-N point: below 4.3 mg/L). The parameters for the RMA2 (depth-averaged two-dimensional flow model) and RMA4 (depth-averaged two-dimensional water-quality model) were determined by sensitivity analysis. Result of parameter estimation for RMA2 and RMA4 models is 1,000 Pa․s of the eddy viscosity, 20 of the Peclet number, 0.025 of the Manning coefficient, and 1.0 m2/s of the diffusion coefficient. We have evaluated the effects of water-quality enhancement of the selected alternatives by numerical simulation technique with the models under the steady-state flow condition and the time-variant transport condition. Because of no-resuspension from river bottom and considering BOD as conservative matter, these simulation results slightly differ from real phenomena. In the case of 50 m3/s of Daejeo-gate inflow, two-dimensional flow pn results result represents that small velocity occurs in the Pyungkang Stream and no flow in the Maekdo River. In the WNR, there occurs the most rapid flow near timhae-bridge. In the WNR, changes of water-quality for the four selected simulation cases(6, 10, 30, 50 m3/s of the Daejeo-gate inflow) were predicted. Since the Daejeo-Gate and the Noksan-Gate can be opened up to 7 days, it would be found that sustainable inflow of 30 m3/s at the Daejeo-gate makes BOD in the WNR to be under the target of water-quality.

The purpose of this study is to analyze the sensitivity of the RMA2 model parameters reflecting the flow characteristics of stream junction and thus understand the hydraulic characteristics of the channel confluence flow. This study dealt with the input parameters of the RMA-2 model, a two-dimensional numerical analysis model widely used for researches both at home and abroad. The parameters of the RMA-2 model are roughness coefficient, turbulent diffusion coefficient, Coriolis forces latitude, Density, and mesh size. This study those parameters estimated from actual heavy rainfall, and varied the parameter size by (-)30%～+30% to review the characteristics of the flow characteristics of the channel section. Weobserved that when the ratio of the channel width was relatively small, the smaller the approaching angle was, the farther from the junctions became the generating place of the maximum flow velocity, however, when the ratio of the channel width was relatively large, the larger the approaching angle was, the farther the generating place of the maximum flow velocity from the junctions became. In particular, the distance between junctions and the place where the maximum flow velocity generated showed an absolute correlationover 90% of the relative channel width, but an inverse relationwas found when the distance to the place where the flow velocity generated was shortened as relative the channel width between the main channel and tributary increased.