A Contribution to the Natural Disasters Study in center-South Chile: Environmental effects of the June 25 of 2005 rainfalls at the Metropolitan Area of Concepción city

The June 25 of 2005 exceptional rainfall event that affect the Concepcion metropolitan area is analyzed, considering the flooding and mass remotions processes triggered and their impact on citizens. The subjects were identify the main risk areas and contribute to prepare natural disasters management plans. For the characterization of this rainfall event intensity data for 24 hours, and for 60, 30 and 10 minutes were calculated from the 1971-1999 pluvial registers. Also a review of the natural processes with negative impact on citizens was realized including localization, terrain evaluation and comparison with the Mardones et al (1994) hazards chart. The impacts on citizens, the emergency attendance costs and the evaluation of the disaster management were estimated by interviews, inquiries and statistics compiled by the OREMI (Regional Emergency Bureau), the county authorities, the civil protection responsible and the neighborhood. The disaster situation was triggered by a unique and continuous rainfall event

that registers 158mm/24 hours intensity at Concepcion city, leaving 5224 injured persons, 36 damaged houses and 5 persons dead. Was observed that rainfall over 150 mm in 24 hours has the sufficient capacity to unchain catastrophes and produce destructive effects. For these events, the statistical analysis shows >20 years how recurrente period. The Mardones et al (1994) hazardous areas were validated. An increasing of the flood risks areas with the city sprawl is clear. The general management of the disaster is analyzed and some proposals for optimize it are presented.