In the Dolomitic region, abundant coarse hillslope sediment is commonly found at the toe of rocky cliffs. Ephemeral channels originate where lower permeability bedrock surfaces concentrate surface runoff. Debris flows initiate along such channels following intense rainfall and determine the progressive erosion and deepening of the channels. Sediment recharge mechanisms include rock fall, dry ravel processes and channel‐bank failures. Here we document debris flow activity that took place in an active debris flow basin during the year 2015. The Cancia basin is located on the southwestern slope of Mount Antelao (3264 m a.s.l.) in the dolomitic region of the eastern Italian Alps. The 2.5 km² basin is incised in dolomitic limestone rocks. The data consist of repeated topographic surveys, distributed rainfall measurements, time‐lapse (2 s) videos of two events and pore pressure measurements in the channel bed. During July and August 2015, two debris flow events occurred, following similarly intense rainstorms. We compared rainfall data to existing rainfall triggering thresholds and simulated the hydrological response of the headwater catchment with a distributed model in order to estimate the total and peak water discharge. Our data clearly illustrate how debris entrainment along the channel is the main contributor to the overall mobilized volume and that erosion is dominant when the channel slope exceeds 16°. Further downstream, sediment accumulation and depletion occurred alternately for the two successive events, indicating that sediment availability along the channel also influences the flow behaviour along the prevailing‐transport reach. The comparison between monitoring data, topographical analysis and hydrological simulation allows the estimation of the average solid concentration of the two events and suggests that debris availability has a significant influence on the debris flow volume. © 2020 John Wiley & Sons, Ltd.

中文翻译：

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径流产生的泥石流：在Cancia（意大利东部阿尔卑斯山）沿河道的初始条件和侵蚀沉积动力学观测

在多洛米蒂地区，通常在岩石峭壁的脚趾处发现大量的粗糙山坡沉积物。短暂通道起源于较低渗透率的基岩表面集中地表径流的地方。在强降雨之后，泥石流会沿着这些通道开始流动，并确定通道的逐渐侵蚀和加深。沉积物补给机制包括崩塌，干裂过程和河岸破坏。在这里，我们记录了在2015年活跃的泥石流盆地中发生的泥石流活动。Cancia盆地位于意大利东部阿尔卑斯山白云岩地区的Antelao山（3264 m asl）的西南斜坡上。2.5公里²盆地被切割成白云质的石灰岩。数据包括重复的地形调查，分布式降雨测量，两次事件的时移（2 s）视频以及河床中的孔隙压力测量。在类似的强烈暴雨之后，2015年7月和2015年8月发生了两次泥石流事件。我们将降雨数据与现有的降雨触发阈值进行了比较，并使用分布式模型模拟了源水集水区的水文响应，以估算总的和峰值的排水量。我们的数据清楚地说明了沿通道夹带的碎屑是导致总动员量的主要因素，并且当通道斜率超过16°时，侵蚀占主导地位。在更下游，两个连续事件交替发生沉积物堆积和消耗，表明沿河道的沉积物可利用性也影响了主要运输河段的水流行为。监测数据，地形分析和水文模拟之间的比较允许估算这两个事件的平均固体浓度，并表明碎片的可利用性对碎片流量具有重大影响。©2020 John Wiley＆Sons，Ltd.