Abstract A storm, composed of two delayed cells, hit the Monte Antelao slopes (Dolomites, North Eastern Italy) in the early morning of July 18th, 2009. The resulting runoff triggered two consecutive debris flows along the Rovina di Cancia channel. The detailed topographic data collected before and just after this event allowed an accurate reconstruction of the morphological changes experienced by the channel bed. These data are here used as benchmark to test the ability of numerical models to reproduce the dynamics of a real event, taking into account the morphology changes of the channel bed. The aim is to provide an efficient model for engineering applications on large scales, such as those required by debris flow hazard assessment. A rainfall-runoff transformation is applied to reconstruct the solid-liquid hydrograph needed for computing the debris flow propagation. Two routing models are used: a GIS-based movable bed model, and a widely used fixed bed model (FLO-2D). Although similar results are obtained in terms of areas subjected to deposition, significant differences emerge in terms of mobilized volumes. Only the simulation of both the deposition and entrainment processes allows to reliably reproduce the sediment volumes estimated from the pre- and post-event topographic data. This information is fundamental in any hazard assessment because the volume of sediment mobilized by debris flow events exerts a fundamental control on the extension of areas subjected to inundation and on the thickness of sediment deposits. The capability to reproduce correctly the mobilized volumes also entails a more reliable simulation of the evolution of the peak and volume of the solid-liquid hydrograph as the debris flow propagates downstream, allowing the identification of the channel reach where banks could be overflowed. Conversely, adopting a fixed bed model leads mainly to an underestimation of the both the transported sediments volumes and the area subjected to deposition. As a consequence, the maximum debris flow depth in the portion of the channel subjected to erosion is underestimated and that in the portion of the channel subjected to deposition is overestimated. All these types of information are of great importance for an effective hazard assessment.

中文翻译：

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在对河道内砾石碎屑流进行建模以进行有效的危险评估时侵蚀过程的相关性

摘要 2009 年 7 月 18 日清晨，一场由两个延迟单元组成的风暴袭击了 Monte Antelao 斜坡（意大利东北部多洛米蒂山）。由此产生的径流引发了沿 Rovina di Cancia 海峡的连续两次泥石流。在此事件之前和之后收集的详细地形数据允许准确重建通道床所经历的形态变化。这些数据在这里用作基准来测试数值模型再现真实事件动力学的能力，同时考虑到河床的形态变化。目的是为大规模工程应用提供有效模型，例如泥石流灾害评估所需的模型。应用降雨-径流变换来重建计算泥石流传播所需的固液水位线。使用了两种路由模型：基于 GIS 的可移动床模型和广泛使用的固定床模型 (FLO-2D)。尽管在沉积面积方面获得了类似的结果，但在流动量方面出现了显着差异。只有对沉积和夹带过程的模拟才能可靠地再现根据事前和事后地形数据估计的沉积物体积。这些信息在任何灾害评估中都是至关重要的，因为泥石流事件所调动的沉积物量对受淹没区域的扩展和沉积物沉积的厚度施加了基本的控制。正确再现移动体积的能力还需要更可靠地模拟泥石流向下游传播时固液水位线的峰值和体积的演变，从而可以识别河岸可能溢出的通道到达。相反，采用固定床模型主要导致对输送的沉积物体积和受沉积面积的低估。因此，河道遭受侵蚀的部分的最大泥石流深度被低估，而遭受沉积的河道部分的最大泥石流深度被高估。所有这些类型的信息对于有效的危害评估都非常重要。