The Hydrological Disasters Through Historical Survey in the Serra do Mar Range, Southern Brazil

The establishment of hydrological disasters frequency standard is a difficult task because of the lack of well fitted historical data series. The establishment of these standards through historical surveys in newspapers and historical archives is an option to set minimum frequency data. The data survey for floods and landslides in Southern Serra do Mar range, in southern Brazil, could establish parameters for frequency of hydrological disasters in that area. The research involved digital and analogical bases, including newspaper reports and historical monographs. Altogether 38 hydrological events were identified in the period of 1796-1913 for the region. The data focus on two main periods: the period of 1846-1913, which involved one event every 2.9 years, and 11.2 years for the large-scale events; and the period of 1960-1980, which presented one event every 1.7 years, and 7.4 years for the large-scale events. Based on the economic and human losses, the events of 1796, 1846, 1873, 1883, 1884, 1888, 1907, 1913, 1946, 1960, 1969, 1971, 1975 were very harmful. The most affected areas were the floodplains, with the occurrence of floods, and the mountain regions with landslides and flows. The major higher landslide incidences were associated with railways and highways. Debris flow deposits occurred mainly in the Piedmont areas. About 90% of the events occurred mainly from October to March, corresponding to the rainy season in the region. The survey of historical data proved to be an interesting source for data, which help to compose the picture, although incomplete, of the occurrence of these hydrological phenomena in the region.