山地流域における水・土砂動態モデルの構築

Abstract

中間流・地表面流統合型kinematicwaveモデル, 表層崩壊予測モデル, 石礫型土石流モデルを結合することによって、山地流域を対象とした水・土砂動態モデルを構築する。本モデルは水の流れと土砂の移動を一次元的に解析し、連続的かつ一体的にモデル化するところに大きな特徴がある。本モデルを馬門川流域に適用し、従来用いられてきた二次元型のモデルの計算結果と比較したところ、表層崩壊の予測についてはほぼ同様の結果を得た。さらに、本モデルを単一の斜面素片に適用して土石流の計算を行なった。上流から土石流を流入させた場合には合理的な結果を得たが、上流から洪水流を流入させた場合には、土石流の運動方程式が切り替わるところで土石流流量が不自然に変動する結果となった。

A water and sediment flow model for a mountainous area is developed by combining a rainfall-runoff model, a slope failure model, and a debris flow model. The distinctive feature of this model is to calculate the water and sediment flow with one dimensional flow analysis.The model was applied to the Umakado river basin and the results were compared to those of the two dimensional model, which has been often used to predict the sediment yield from a mountainous area, and it was shown that the two models gave almost similar results. Then the model was applied to single slope unit to conduct debris flow simulations. When a debris flow hydrograph was given as the upstream boundary condition, the results were reasonable. However when a water flow hydrograph was given from the upstream boundary, the output debris flow hydrograph fluctuated unnaturally at which the equation of motion of the debris flow was replaced according as the density of the particles decreased.