본 연구에서는 에너지 방정식에 기초하여 정수 식생이 존재하는 자연하도에 적용 가능한 1차원 수치모형을 제시하였다. 수위계산을 위한 마찰경사는 Darcy-Weisbach의 마찰식에 의해 계산되었다. 각 단면의 전체 Darcy-Weisbach 마찰계수는 하상조도높이, 식생, 식생구역과 비식생구역 사이의 전단저항, 그리고 홍수터와 주수로의 경계면 전단저항을 고려하여 산정하였다. 경계면 마찰계수는 Mertens방법과 Nuding방법에 의해 계산되었다. 제시된 모형을 가상하도에 적용하고 HEC-RAS모형 모의결과와 비교, 검증하였고, 식생밀도 등에 대하여 마찰계수의 민감도 분석을 실시하였다. 모형의 적용성검토를 위하여 독일 Enz강 일부구간을 대상으로 수치모의를 실시하고 실측수위와 비교하였다. 식생이 존재하는 Enz강의 실측수위와 계산수위를 비교한 결과 식생의 영향을 거의 받지 않고 주수로에 흐름이 형성되는 저유량의 경우와 식생의 영향을 지배적으로 받는 고유량 흐름 모두에서 합리적인 수위를 예측하여 제시된 모형의 적용 가능성을 확인하였다.
A 1D numerical model for steady flow, based on the energy equation, was developed for natural rivers with emergent vegetations on floodplains and banks. The friction slope was determined by the friction law of Darcy-Weisbach. The composite friction factor of the each cross section was calculated by considering bottom roughness of the main channel and the floodplains, the flow resistance of vegetations, the apparent shear stress and the flow resistance caused by the momentum transfer between vegetated areas and non-vegetated areas. The interface friction factor caused by flow interaction was calculated by empirical formulas of Mertens and Nuding. In order to verify the accuracy of the suggested model, water surface elevations were calculated by using imaginary compound channels and the results of calculations were compared with that of the HEC-RAS. The sensitivity analysis was performed to confirm changed friction factors by vegetations density etc. The suggested model was applied to the reach of the Enz River in Germany, and estimated water surface elevations of the Enz River were compared with measured water surface elevations. This model could acceptably compute not only water surface elevations with low discharge but also that with high discharge. So, the suggested model in this study verified the applicability in natural rivers with emergent vegetations.
