| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 98 === This study analyzes water flow on an inclined plane under a uniform rainfall by a semi-analytical approach. The flow field is divided into two regions: water layer and soil layer. The soil layer is a porous medium. The flow inside the soil layer is a porous media flow. We observe how the soil affects the overland flow, and consider the flow velocity is nonzero on the ground surface.
The velocity distribution in each layer can be solved by applying Song’s(1993) laminar model and Navier-Stokes equation. Then the flow discharge is obtained by integrating the flow velocity. After solving the velocity of overland flow, the influence of each parameter will be discussed. By using Runge-Kutta method, the flow depth can be found. Then the relationship between flow velocity and water depth is built.
There are two kinds of thickness, finite and infinite, that could be discussed. After the solutions of overland flow are obtained, water depth could be observed by changing the parameter of incline plane. We found that the water depth decreases with rainfall intensity and increases with the slope, permeability and thickness of soil layer. The slope factor affects the water depth most of all. When the rainfall intensity is changed, the water surface line will translate up and down, but its pattern doesn’t change by the rainfall intensity. Different kinds of soil are also compared. It is obvious that the water depth of ocarse sand is the lowest. Since the permeabilities in silt and clay are low, the water depths in such soils are almost the same as that in impermeable ground.
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