Studies regarding an active basin-and-fan system located in South Calabria, along the southern side of the Aspromonte Massif, near San Lorenzo (Reggio Calabria) are reported, Fig. 1. The rocks cropping out in the study zone belong to the Stilo Unit (BONARDI et al., 1984) and are mainly represented by phyllites and shales.The morphological and sedimentological evolution of the active basin-and-fan system indicates how relevant can be shortterms trending and cyclical modifications of such systems, though maintaining a constant overall aspect (SORRISO-VALVO,2010).Anthropic interference is also relevant in either passive and active sense, natural processes dominating in the feeder basin area, whilst check dams exert a strong control on fan deposition processes and again natural stream erosion processes dominate in the fan tip zone.As a general result, though being now quite impossible to measure the volume of parent rock actually eroded from the basin slopes during the considered time period in an accurate way, there is evidence of large volumes of debris being eroded, transported along the drainage system to the fan and main streambeds, and from there evacuated by recurrent floods (Fig. 2).The great deal of debris budget transiting on the stream-fan system, stands for a level of hazard for flash floods, hyperconcentrated flows and debris flows much higher than thatinferable from one-time visual survey. In addition, the check dams built in Seventies, being buried, are no longer so relevant as regards the magnitude of processes on feeder channel and the fan. This may explain why local residents continue to use the areas close to on or around the fan and do not perceive the level of danger they are exposed to, should a major trigger event occur, capable to suddenly mobilize a large amount of debris, either from the incipient landslides in the basin scar or from stream beds budget.
Basin-and-fan system morphodynamics and related hazards. S. Lorenzo, Calabria, Italy
ROBUSTELLI, Gaetano;
2012-01-01
Abstract
Studies regarding an active basin-and-fan system located in South Calabria, along the southern side of the Aspromonte Massif, near San Lorenzo (Reggio Calabria) are reported, Fig. 1. The rocks cropping out in the study zone belong to the Stilo Unit (BONARDI et al., 1984) and are mainly represented by phyllites and shales.The morphological and sedimentological evolution of the active basin-and-fan system indicates how relevant can be shortterms trending and cyclical modifications of such systems, though maintaining a constant overall aspect (SORRISO-VALVO,2010).Anthropic interference is also relevant in either passive and active sense, natural processes dominating in the feeder basin area, whilst check dams exert a strong control on fan deposition processes and again natural stream erosion processes dominate in the fan tip zone.As a general result, though being now quite impossible to measure the volume of parent rock actually eroded from the basin slopes during the considered time period in an accurate way, there is evidence of large volumes of debris being eroded, transported along the drainage system to the fan and main streambeds, and from there evacuated by recurrent floods (Fig. 2).The great deal of debris budget transiting on the stream-fan system, stands for a level of hazard for flash floods, hyperconcentrated flows and debris flows much higher than thatinferable from one-time visual survey. In addition, the check dams built in Seventies, being buried, are no longer so relevant as regards the magnitude of processes on feeder channel and the fan. This may explain why local residents continue to use the areas close to on or around the fan and do not perceive the level of danger they are exposed to, should a major trigger event occur, capable to suddenly mobilize a large amount of debris, either from the incipient landslides in the basin scar or from stream beds budget.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
