Marco Cavalli, Lorenzo Marchi, Massimo Arattano, 2013, Protocol for Debris-flow Monitoring, pp.1–35, 2013,
URL: http://www.cnr.it/prodotto/i/239899

Monitoring of debris flows in instrumented catchments permits collection of data on these phenomena and provides a valuable link with geomorphological and topographical observations of erosion, sediment supply and channel evolution. The recorded data can serve as a basis for implementing of early warning systems that provide defense against debris-flow risk. The quantification of sediment volumes transported by debris flows along with their temporal frequency, timing, flow characteristics (i.e. velocity, flow depth, peak discharge, density) are of crucial importance for hazard assessment, land-use planning and design of torrent control structures. In addition, instrumented basins provide highquality information for deriving regional thresholds of rainfall intensity and/or cumulated values for debris-flow triggering to be used in warning systems. Japan and China have pioneered debris-flow monitoring (Okuda et al., 1980; Zhang, 1993) and sites instrumented in these countries still play a significant role in debris-flow research, also thanks to the long time series of recorded data (Hu et al., 2011a, b; Suwa et al., 2011). In Taiwan, the frequent occurrence of high-magnitude debris flows with severe damage to settlements has urged the installation of equipment for monitoring debris flows and for issuing warnings in a number of sites (Yin et al., 2011). Amongst early experiences on instrumental observations of debris flows in the United States, are the monitoring campaigns by Pierson (1986) in channels on the flanks of Mount St. Helens. More recently, the installation of monitoring equipment at Chalk Cliffs, a small, very active catchment in the Colorado Rocky Mountains, has started providing valuable information and data on debris-flow triggering and flow dynamics (Coe et al., 2008; McCoy et al., 2011). In Europe, the first catchment instrumented for debris -flow monitoring was probably the Moscardo Torrent in the Eastern Italian Alps (Arattano et al., 1997; Marchi et al., 2002). Other sites were 3 instrumented in the late 1990s and early 2000s in Italy (Tecca et al., 2003) and Switzerland (Hürlimann et al., 2003). Amongst these monitoring sites, the Illgraben catchment (Switzerland) deserves to be mentioned because of innovative measurements on forces and pore fluid pressure in debris flows (Mc Ardell et al., 2007) and channel-bed erosion (Berger et al., 2011). Recent development of monitoring activities in Europe, which include installations in Austria (Kogelnig et al., 2011), France (Navratil et al., 2012; 2013b), and Spain (Hürlimann et al., 2011) indicates the high interest for this sector of debris-flow studies. The number of monitoring sites and the amount of recorded data on debris flows remains still limited if compared to landslides and fluvial sediment transport. Moreover, the large variability of debris-flow features, their dependence on local topographical, geological and climate conditions makes the collection of more data in instrumented catchments of the utmost importance. This protocol aims at describing minimum requirements for a debris-flow monitoring site and illustrating the existing sensors and methods of measurements and data collection. In the SedAlp Project several catchments are instrumented for debris-flows monitoring_ Rio Gadria by the Autonomous Province of Bozen-Bolzano (PP1) with the collaboration of CNR-IRPI (PP4), Rio Chiesa by ARPAV (PP2), Moscardo Torrent by CNR-IRPI (PP4), Manival and Réal torrents by Irstea (PP7). Monitoring concepts of these pilot areas were used to draft the protocol; devices and measurements methods implemented in European debris-flow monitoring sites outside the project were also considered in order to provide a comprehensive view of existing methods for debris-flow monitoring.

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