Analisi di eventi alluvionali nel bacino del Torrente Vallone in territorio di Apricena (Foggia)

Analysis of floodings in the drainage basin of the Vallone Stream (Apricena, district of Foggia, Southern Italy) ABSTRACT: The town of Apricena is crossed by a channel named “Canale Vallone”; this channel represents the lower part of a branching stream, draining an area extending over 27 km2. The area is marked by the occurrence, in the higher part of the basin, of active alluvial fans located at the base of a steep calcareous slope. In the middle part of the basin, consituted by a wide nearly-flat surface, streamlines are poorly recognizable. In this part, intense rainfalls cause soil erosion due to sheet flood and rill processes. In the lower part of the basin, a channel collects the stream lines coming from different directions and delivery the water into the Candelaro River, after crossing Apricena, near the old centre of the town. During a rainy period between the end of August anf the beginning of September 2002, the overflow of the channel caused the flooding in a part of the town with severe damage to the buildings, to the public facilities and to the crops in the sorrounding countryside. Analysis of pluviometric data shows that the rainfall heights causing the floods in Apricena maybe regarded to be lower than the maximun expected heights calculated considering the meteo-climatic conditions of the area. Rainfall heights, measured at Apricena during the rainy period of 2002, result lower also if compared to the maximum historical rainfall heights recorded at the meteorological stations in the area. Floods were caused by several contributory factors, such as the distribution of rainfalls over time and the arrangement of the territory, planned in the last decades without taking into the right account the actual morphohydrological and climatic features of the area. Key terms: Apricena, Gargano, Flooding, Rainfalls Termini chiave: Apricena, Gargano, Evento alluvionale, Precipitazioni