Measurement of soil characteristics controlling runoff processes and model development

1.在土壤结构调查的基础上估算土壤水力性质我们发展了一种根据土壤微观结构估算土壤孔隙分布的新方法。微结构是由离散单元法(DEM)数值生成的，DEM最初是用来描述岩石块体运动的(Cundall和Strack，1979)。离散单元法通过根据运动方程追踪每个粒子来模拟一组离散粒子的集体运动。我们使用这种方法以随机的方式将不同半径的土壤颗粒在比体积中包装，并重复这个过程来评估土壤包装的孔隙分布。2.考虑土壤性质的水文模型的发展和应用我们建立了几个考虑土壤物理性质的水文模型，并应用于流域研究。首先，在水的物理力学基础上，建立了森林坡面的径流模型。在此基础上，建立了基于…的森林坡面径流模型山坡表面更低和/或更低(Mouri等人)。(2003年)、立川(2004年))。Mouri等人(2003)开发了一种算法来预测流域尺度上的水和泥沙的动态行为。在他们的算法中，将一个盆地划分为多个山坡，并对每个山坡应用包含土壤特性的运动学波浪模型来预测水和泥沙的运动。Tchikawa等人(2004)建立了包含坡面饱和-非饱和水流机制的水位-流量关系方程。该方程能够描述从枯水期到丰水期的各种流型。其次，我们基于包含土壤物理特性的水流模型(Ichikawa等人(2003)，Ichikawa等人(2003))发展了一个土壤径流模型。在该模型中，土壤侵蚀速率是由坡面水流深度确定的摩阻速度来计算的。第三，将土壤水力特性与地表微地形相结合，建立了二维浅层水流与一维饱和-非饱和地下水流耦合模型，用于精确预报降雨径流过程的微观物理过程。较少

1.Estimation of soil hydraulic properties based on the investigation of soil structuresWe develop a new method to estimate pore size distributions from microstructures of the soils. The microstructures are numerically generated by the distinct element method(DEM), which was originally proposed to describe rock block movement (Cundall and Strack, 1979). The distinct element method simulates how a group of discrete particles move collectively by tracing each particle on the basis of equation of motion. We use this method to pack soil particles with various radius in specific volume in random manner, and repeat this procedure to evaluate pore size distributions of soil packages.2.Development and applications of hydrological models incorporating soil propertiesWe developed several hydrological models which incorporate soil physical properties and applied to study catchments. First of all, we developed a flow routing model for forest hillslopes, on the basis of physical mechanics of water f … More low on and/or beneath the hillslope surface (Mouri et al. (2003), Tachikawa (2004)). Mouri et al.(2003) developed an algorithm to predict dynamic behavior of water and sediment in the basin scale. In their algorithm, a basin is divided into a number of hillslopes, and a kinematic wave model incorporating soil characteristics is applied to each hillslope to predict water and sediment movement. Tachikawa et al.(2004) developed a stage-discharge relationship equation incorporating saturated-unsaturated flow mechanism of hillslopes. This equation is able to describe a wide range of flow patterns from dry to wet periods. Secondly, we developed a soil runoff model based on water flow models which incorporate soil physical characteristics (Ichikawa et al.(2003), Ichikawa et al.(2003)). In this model, rate of soil erosion is calculated using friction velocity, which is determined from overland flow depth. Thirdly, we developed a coupled model of two dimensional shallow surface water flow and one dimensional saturated-unsaturated subsurface flow to precisely predict micro physics of rainfall-runoff processes, by incorporating soil hydraulic properties and micro topography of soil surface. Less