坡面土体的崩塌活动是泥石流形成的初始过程。为了研究降雨条件下该过程中蕴含的随机性,选择典型泥石流源地坡面进行人工降雨实验,观测坡面径流和坡面土体活动特征。结果表明:坡面径流的产生与坡面土体的供给是2个相对独立的过程;坡面产流过程在时间上具有连续性,空间上具有均匀性,规模上具有稳定性;即使是在恒定的降雨强度条件下,泥石流的源地土体活动也表现为一个离散的土体崩塌序列,具有时间上的间歇性、空间上的聚集性、规模上的随机性,且在时间上服从泊松分布,在规模上服从规模-频率的幂率关系;坡面的水土过程是不完全同步的,泥石流的形成依赖于坡面土体补给的时间、空间和规模分布,这也决定了泥石流阵流的多变和流量的涨落。建立基于土体活动特征的随机性补给模型,结合分布式水文模型,是建立科学的泥石流预报模型的有效方法。 更多还原
 

The runoff yield and slope failures are the source of debris flows in watersheds. The previous study focuses on the deterministic mechanism formation of slope failures for debris flow initiation and hydrological processes for debris flow runoff calculation. This paper aims to reveal and discuss the randomness process of slope failures. Artificial rainfall experiment was conducted on selected typical debris flow source region to observe the movement features of slope runoff and soil body. Results showed that slope failure and runoff formation are two separated processes. Runoff generation was continuous, evenly and stably distributed on slope. Slope failure presented a sequence of soil body collapse with the features of intermittence in time, aggregation in space, and remarkable fluctuation in magnitude. Slope failures time interval fit the Poisson distribution and its magnitude fit the power-law. The soil and water supplies were unsynchronized, the debris flow initiation depend not only on the flood generation, but also on the spatiotemporal characteristics of the slope failure processes, which leads to high variety and fluctuation of debris flows even under the same rainfall condition. This study contributes the debris flow formation and runoff calculation by taking debris flow formation as a randomness and discontinuous process and revealing the spatial characteristics of slope failures.