Effect of antecedent-hydrological conditions on rainfall triggering of debris flows in ash-fall pyroclastic mantled slopes of Campania (southern Italy)
Effect of antecedent-hydrological conditions on rainfall triggering of debris flows in ash-fall pyroclastic mantled slopes of Campania (southern Italy)
复制标题
DOI：
10.1007/s10346-015-0647-5
复制
发表时间：
2016-10
期刊：
影响因子：
6.7
通讯作者：
E. Napolitano;F. Fusco;R. Baum;J. Godt;P. De Vita
中科院分区：
文献类型：
--
作者：
E. Napolitano;F. Fusco;R. Baum;J. Godt;P. De Vita
坎帕尼亚平原和索马-维苏威火山（意大利南部）周围的山区是意大利最危险的地区之一，因为降雨引发的泥石流沿着火山灰火山碎屑土壤覆盖的斜坡反复发生。在这个地貌框架中，降雨模式、多层灰烬火山碎屑沉积物内发生的水文过程以及土壤前期湿度状况是评估触发降雨条件和相关危害时需要考虑的主要因素。本文介绍了对 1998 年 5 月发生在萨尔诺山脉的四个代表性泥石流源区进行的基于滑坡物理模型重建、现场水文监测以及水文和边坡稳定性建模的综合分析实验研究的结果。 2011 年期间，利用张力计和 Watermark 压头传感器以及降雨量和气温记录站进行了水文监测。利用测得的压力水头的时间序列来校准 2011 年火山碎屑土地幔的水文数值模型，考虑到降雨量和气温监测数据的可用性，该模型从 2000 年开始重新运行了 12 年。这种方法使我们能够在日时间尺度上重建长期的压头状况，这代表了不同气象条件下约11个水文年。基于该模拟时间序列，选择平均冬季和夏季水文条件对样本边坡进行水文和稳定性建模，并通过确定性方法确定强度-持续时间降雨阈值。主要结果中，发现相反的冬季和夏季前期压力水头（土壤湿度）条件对降雨触发事件的强度和持续时间具有显着的控制作用。从冬季到夏季的条件需要大幅增加强度和/或持续时间才能引发山体滑坡。研究结果确定了一种方法来解释与灰烬火山碎屑土地幔内水文过程季节性相关的不同灾害条件。此外，他们强调了另一个重要的不确定因素，该因素可能影响降雨阈值，从而引发通过经验方法重建的浅层滑坡。
Mountainous areas surrounding the Campanian Plain and the Somma-Vesuvius volcano (southern Italy) are among the most risky areas of Italy due to the repeated occurrence of rainfall-induced debris flows along ash-fall pyroclastic soil-mantled slopes. In this geomorphological framework, rainfall patterns, hydrological processes taking place within multi-layered ash-fall pyroclastic deposits and soil antecedent moisture status are the principal factors to be taken into account to assess triggering rainfall conditions and the related hazard. This paper presents the outcomes of an experimental study based on integrated analyses consisting of the reconstruction of physical models of landslides, in situ hydrological monitoring, and hydrological and slope stability modeling, carried out on four representative source areas of debris flows that occurred in May 1998 in the Sarno Mountain Range. The hydrological monitoring was carried out during 2011 using nests of tensiometers and Watermark pressure head sensors and also through a rainfall and air temperature recording station. Time series of measured pressure head were used to calibrate a hydrological numerical model of the pyroclastic soil mantle for 2011, which was re-run for a 12-year period beginning in 2000, given the availability of rainfall and air temperature monitoring data. Such an approach allowed us to reconstruct the regime of pressure head at a daily time scale for a long period, which is representative of about 11 hydrologic years with different meteorological conditions. Based on this simulated time series, average winter and summer hydrological conditions were chosen to carry out hydrological and stability modeling of sample slopes and to identify Intensity-Duration rainfall thresholds by a deterministic approach. Among principal results, the opposing winter and summer antecedent pressure head (soil moisture) conditions were found to exert a significant control on intensity and duration of rainfall triggering events. Going from winter to summer conditions requires a strong increase of intensity and/or duration to induce landslides. The results identify an approach to account for different hazard conditions related to seasonality of hydrological processes inside the ash-fall pyroclastic soil mantle. Moreover, they highlight another important factor of uncertainty that potentially affects rainfall thresholds triggering shallow landslides reconstructed by empirical approaches.