降雨移动方向对坡面径流的影响机理

Impact of rainfall-movement direction on hillslope runoff generation

通过基于物理概念的水文响应数值模拟,研究了降雨移动方向对坡面地表径流的影响机理.模拟中降雨移动速度不变,分别沿模拟坡面轴线向上和向下移动,降雨强度设为恒定值4.0×10-5m/s.通过分析下游出口边界处的流量过程曲线和坡面轴线上观测点的压强水头变化,分析降雨移动对坡面径流的影响.结果表明,降雨移动方向主要是改变坡面水文条件、影响坡面水文响应,进而影响地表径流特征.当降雨沿坡面向上游移动时,坡面出口处的流量过程曲线的径流上升更早、径流峰值略低、径流从开始发生至到达峰值所需时间更长、径流整体历时略长;当降雨沿坡面向下游移动时,坡面中部及靠近下游边界部分在降雨开始前就已经饱和,从而影响产流,坡面全部达到饱和的时间更早,坡面下游边界饱和的时间略短.

The impact of rainfall-movement direction on the hillslope runoff generation was investigated via physics-based hydrological numerical simulation. Rainfall moved downslop as well as upslope along the simulated plot＇s axis in the simulations, combining with constant rainfall velocity and intensity （4.0 × 10^-5 m/s）. The hydrograph at the downstream boundary and the pressure head information at the observation points along the plot＇s axis were analyzed to investigate the impact of rainfall-movement direction. Results show that the rainfall-movement direction affects the surface runoff characteristics by changing the hillslope hydrological condition, and subsequently modifies the hydrological response. When rainfall moves upslope, the hydrograph at the downstream boundary is featured by earlier rising limb, lower peak flow, longer time for discharge to reach the peak value, and longer runoff period. When rainfall moves downslope, the middle part of the hillslope and the area around the downstream boundary get saturated before rainfall starts there, resulting in different runoff characteristics featured by earlier saturation for the entire hillslope and shorter saturation period for the downstream boundary.