만곡하천의 자갈하상재료 분포에 따른 한계수류력 평가 = Estimating Critical Stream Power by the Distribution of Gravel-bed Materials in the Meandering River

국문 초록 (Abstract)

산지하천의 자갈하상재료 분포는 최근 특정규모 홍수의 수류력에 의한 유사 이송 및 퇴적 과정에 의해 형성되며, 장갑화된 하천에서 한계수류력을 평가하는 것은 안정하도설계를 위해 중요하다. 자갈하상 하천 종단지점과 만곡부 일정구간의 세부지점에대한하상재료의입도분포를조사하고, 한계유속 및 한계수류력을 평가하였다. 자갈하상 재료에 대한 Yang의 한계단위수류력과 Bagnold의 한계수류력은 상류로 갈수록 급격히 증가했다. 계획홍수량에 근거한 무차원 전단응력은 Shields 도표에서대부분조사지점의자갈하상재료가소류사형태로이동하는것으로평가되었다. 만곡부에 대한 평균입경은 상류 유입수의 1차 수충지점에서 가장 컸으며, 반사흐름에 의한 2차 수충지점에서 두 번째로 큰 입경을 보였다. 수충직하류지점들에서상대적으로작은평균입경을보였다. 만곡부의 평균한계유속 범위는0.77~2.60m/s의 범위이며, 한계단위수류력은 경사가 급한 1차 수충부에서는 상당히 컸다. 한계수류력의 분포는 7~171W/m2의 범위로 하천 횡단보다는 종단에 따른 변화가 뚜렷했고, 만곡 외측 1차 수충지점과 반사흐름 2차 수충지점에서 크게 작용하는 것으로 평가되었다.

다국어 초록 (Multilingual Abstract)

The distribution of gravel-bed materials in mountainous river is formed by the process of deposition and transportation of sediment responding to stream power of the latest flood that is over the certain scale. The particle size of bed material was surveyed in the longitudinal points of river and detail points of a specific meandering section and used to estimate the critical velocity and stream power. Yang's critical unit stream power and Bagnold's critical stream power for gravel-bed materials increased with the distance from downstream to upstream. Dimensionless shear stress based on the designed flood discharge in Shields diagram was evaluated that the gravel-bed materials in most survey points may be transported as form of bedload. The mean diameter in the meandering section was the biggest size in first water impingement point of inflow water from upstream and the second big size in second water impingement point by reflection flow. The mean diameters were relatively the small sizes in points right after water impingement. The range of mean critical velocity was 0.77~2.60 m/s and critical unit stream power was big greatly in first water impingement point. The distribution of critical stream power, range of 7~171 $W/m^2$, was shown that variation in longitudinal section was more obvious than that of cross section and estimated that critical stream power may be affected greatly in first and second water impingement point.

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