The intense quarrying activities in the Carrara marble district (Apuan Alps, Italy) caused the formation of widespread and thick quarry waste deposits, which lie on steep slopes and invade many valley bottoms. Unfortunately, due to its geographical position and conformation the Apuan Alps region is one of the rainiest in Italy, in which rainstorms often cause floods, landslides, debris flows and deaths. On September 23, 2003 a short and intense downpour hit the marble basins and produced more than 500 debris flows and landslides, which caused heavy damage, one death and the interruption of the quarry working. The evaluation of the stability conditions of the quarry dumps is actually very difficult due to the lack of knowledge of the geotechnical features of such deposits. They are in fact characterized by abundant boulders included in a matrix composed by sand, silt and clay in variable percentage. For such reasons, an empirical approach, based on the knowledge of the rainfall characteristics able to trigger mass movements represents an important step in order to plan an alert system for the quarry activities and the population which lives in the valley bottoms (the city of Carrara, almost 70,000 inhabitants, is located at the mouth to the plain of the main torrent draining the marble basins). The methodology used in this research is well-known in scientific literature, but was never applied to anthropic deposits. Thus, aimed at contributing to individuate the debris flow hazard in this area, the most significant rainfall events recorded between 1950 and 2005 in the marble basins were collected and analyzed. Then, an accurate historical research on the effects produced by the rainfall events was carried out in order to examine the relationship between debris flows initiation and rainfall parameters. A critical threshold curve in term of duration, intensity, total amount and mean annual precipitation was defined for 3 raingauges in the marble basins. Such curves were also compared with the thresholds proposed for other regions of the Apuan Alps, finding critical rainfall thresholds for the quarry wastes lower than those for the natural colluvial covers.
Critical rainfall thresholds for triggering debris flows in marble quarry wastes: the example of the Carrara basin (Apuan Alps, Italy)
GIANNECCHINI, ROBERTO;D'AMATO AVANZI, GIACOMO ALFREDO
2008-01-01
Abstract
The intense quarrying activities in the Carrara marble district (Apuan Alps, Italy) caused the formation of widespread and thick quarry waste deposits, which lie on steep slopes and invade many valley bottoms. Unfortunately, due to its geographical position and conformation the Apuan Alps region is one of the rainiest in Italy, in which rainstorms often cause floods, landslides, debris flows and deaths. On September 23, 2003 a short and intense downpour hit the marble basins and produced more than 500 debris flows and landslides, which caused heavy damage, one death and the interruption of the quarry working. The evaluation of the stability conditions of the quarry dumps is actually very difficult due to the lack of knowledge of the geotechnical features of such deposits. They are in fact characterized by abundant boulders included in a matrix composed by sand, silt and clay in variable percentage. For such reasons, an empirical approach, based on the knowledge of the rainfall characteristics able to trigger mass movements represents an important step in order to plan an alert system for the quarry activities and the population which lives in the valley bottoms (the city of Carrara, almost 70,000 inhabitants, is located at the mouth to the plain of the main torrent draining the marble basins). The methodology used in this research is well-known in scientific literature, but was never applied to anthropic deposits. Thus, aimed at contributing to individuate the debris flow hazard in this area, the most significant rainfall events recorded between 1950 and 2005 in the marble basins were collected and analyzed. Then, an accurate historical research on the effects produced by the rainfall events was carried out in order to examine the relationship between debris flows initiation and rainfall parameters. A critical threshold curve in term of duration, intensity, total amount and mean annual precipitation was defined for 3 raingauges in the marble basins. Such curves were also compared with the thresholds proposed for other regions of the Apuan Alps, finding critical rainfall thresholds for the quarry wastes lower than those for the natural colluvial covers.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
