Hydrogeomorphic processes and torrent control works on a large alluvial fan in the eastern Italian Alps

Abstract

Abstract. Alluvial fans are often present at the outlet of small drainage basins in alpine valleys; their formation is due to sediment transport associated with flash floods and debris flows. Alluvial fans are preferred sites for human settlements and are frequently crossed by transport routes. In order to reduce the risk for economic activities located on or near the fan and prevent loss of lives due to floods and debris flows, torrent control works have been extensively carried out on many alpine alluvial fans. Hazard management on alluvial fans in alpine regions is dependent upon reliable procedures to evaluate variations in the frequency and severity of hydrogeomorphic processes and the long-term performance of the torrent training works. An integrated approach to the analysis of hydrogeomorphic processes and their interactions with torrent control works has been applied to a large alluvial fan in the southern Carnic Alps (northeastern Italy). Study methods encompass field observations, interpretation of aerial photographs, analysis of historical documents, and numerical modelling of debris flows. The overall performance of control works implemented in the early decades of 20th century was satisfactory, and a reduction of hazardous events was recognised from features observed in the field and in aerial photographs, as well as from the analysis of historical records. The 2-D simulation of debris flows confirms these findings, indicating that debris flow deposition would not affect urban areas or main roads, even in the case of a high-magnitude event. Present issues in the management of the studied alluvial fan are representative of situations frequently found in the European Alps and deal with the need for maintenance of the control structures and the pressures for land use changes aimed at the economic exploitation of the fan surface.

Debris flood hazard documentation and mitigation on the Tilcara alluvial fan (Quebrada de Humahuaca, Jujuy province, North-West Argentina)

“…Moreover, the aggradation and erosion phenomena in the channel have not been mapped at a detailed scale after major past events. Even though it is unquestionable that these studies are mandatory in order to design countermeasure works (Marchi et al, 2010), though the analysis of landforms and the description of the events given by the local population it is possible to outline two possible mitigation scenarios for the village of Tilcara. The first scenario is conservative and it consists in the periodical removal of the material accumulating in the alluvial fan, and in the maintenance and reinforcement of natural and artificial levees (see Fig.…”

Runout and deposit morphology of Bingham fluid as a function of initial volume: implication for debris flow modelling

“…One of the key input parameters for hazard assessment is the volume of flow-type landslides, and in fact, the potential volume of past events is commonly used as a measure of event magnitude (Davies 1982;Legros 2002;Chang et al 2011, among others). Initial landslide volume can be estimated by different methodologies depending on the mathematical description selected, with hydrological, geomorphological or both kind of features taken into account (Gartner et al 2008;Marchi et al 2010;Chang et al 2011;Friedel 2011;Tsai et al 2011;Robinson and Clynne 2012;Rocco et al 2012). Other authors including Yoshida and Sugai (2007) or Santi and Morandi (2013) propose measuring and simplifying the deposit dimensions using common methods such as truck remobilization or field observations (thickness, sediment width, and flow-path length).…”

Debris-Flow Hazard Assessment and Methods Applied in Engineering Practice

“…The commercially available Flo-2D simulation model [O'Brien et al, 1993] has possibly been most widely applied to natural debris flows or compared with other models [e.g., Chuang et al, 2000;Sosio et al, 2007;Armento et al, 2008;Bertolo and Bottino 2008;Marchi et al, 2010]. In some of these applications the Bingham model parameters were inferred from the measured rheology of samples of the fine material slurry.…”