Multiscale map analysis in alluvial fan flood-prone areas

Abstract

Several case studies of geomorphological mapping at various scales in order to identify areas prone to alluvial fan flooding are presented in this paper. The selected areas are located in southern Italy and are representative of a geomorphic unit (foothills consisting of coalescent alluvial fans) found throughout the southern Apennines. The medium-scale approach represents the best tool to identify areas susceptible to flooding, using detailed geomorphological mapping of fan systems. It can be considered a preliminary analysis, which provides important information for large areas and identifies zones which need further investigation. Large-scale map analysis may be applied to a single fan and used to distinguish fan portions prone to different degrees of hazard exposure, thus providing accurate information for decision-makers who are called upon to plan hazard management. In both cases, analysis based on detailed geological and geomorphological field surveys is often coupled with remotely sensed data.Keywords: Medium and Large scale maps; urbanized alluvial fan; flooding susceptibility; GIS applications; Southern Italy; debris flow 1. Introduction Piedmont areas consisting of coalescent alluvial fans are commonly occurring geomorphological units worldwide (Bull, 1968(Bull, , 1977. Due to their gentle slope, they are often prime spots for urban development. However, during intense storms, they may be affected by flooding and/or debris flow processes, thus becoming prone to hazardous phenomena.Flood susceptibility assessment in fan contexts is a major challenge, although to date this has received little attention. Papers dealing with other kinds of natural hazards such as landslides in mountain and hill areas (Aleotti & Chowdhury, 1999;Capparelli, Versace, & Biondi, 2013;Cascini, Bonnard, Corominas, Jibson, & Montero-Olarte, 2005;Castelli et al., 2002; JTC-1, 2008;Olivares & Picarelli, 2003;Sorbino, Sica, & Cascini, 2010) and flood hazards in floodplains (Canuti & Casagli, 1996;Guzzetti, Stark, & Salvati, 2005; Jalayer et al., 2014;Van Westen, 2000) are more numerous than those regarding flood susceptibility assessment in fan contexts.

Heavy Rainfall Events and Mass Movements in the Funchal Area (Madeira, Portugal): Spatial Analysis and Susceptibility Assessment

“…A mixture of varied debris, from particles to large rocky blocks and tree trunks, adds to the water flow and these dynamics can be associated with the so-called torrent processes. Similar occurrences have been described in mountainous areas, such as the Austrian Alps [5], Southern Italy [6,7], and France [8].…”

Remotely sensed rivers in the Anthropocene: state of the art and prospects

“…Such historical large-scale studies are usually based on relatively few observations (at best decadal), mainly aerial photos (e.g. Belletti et al, 2014), manually digitized historical maps (Scorpio et al, 2016;Meybeck and Lestel, 2017) or a combination of aerial photos and maps (e.g. Surian et al, 2009).…”

Geomorphic response to late Quaternary tectonics in the axial portion of the Southern Apennines (Italy): A case study from the Calore River valley

“…Between the late Lower Pleistocene and the Holocene, these basins were gradually filled with continental deposits (Amato et al, , 2014(Amato et al, , 2017b, while several generations of slope and alluvial fan systems grew at the feet of these tectonically active mountain fronts (Brancaccio et al, 2000;Santangelo et al, 2012). The alluvial fans generally consist of alternating layers of reworked carbonate conglomerates, volcaniclastic matrix-supported gravels, sandy gravels with a high content of volcaniclastic materials, paleosols and tephra layers (Pareschi et al, 2002;Bellucci et al, 2003;Zanchetta et al, 2004;Bisson et al, 2007;Massa and Zuppetta, 2009;Santangelo et al, 2012;Scorpio et al, 2015). Their growth was driven by floods, hyperconcentrated flows and debris flow events (Santo et al, 2011(Santo et al, , 2017Santangelo et al, 2012;Rosskopf and Scorpio, 2013;Scorpio and Rosskopf, 2016).…”