Natural hazards in the mountainous region of Rio de Janeiro state,
Brazil: rainfall erosivity as an early warning index
Rainfall erosivity is defined as the potential of rain to cause erosion.
It has great potential for application in studies related to landslides
and floods, in addition to water erosion. The objectives of this study
were: i) to model the Rday using a seasonal model for the Mountainous
Region of the State of Rio de Janeiro (MRRJ); ii) to adjust thresholds
of the Rday index based on catastrophic events which occurred in the
last two decades; and iii) to map the maximum daily rainfall erosivity
(Rmaxday) to assess the region’s susceptibility to rainfall hazards
according to the established Rday limits. The fitted Rday model
presented a satisfactory result, thereby enabling its application as an
estimator of the daily rainfall erosivity in MRRJ. Events that resulted
in Rday > 1,500 MJ.ha-1.mm.h-1.day-1 were those with the
highest number of fatalities. The spatial distribution of Rmaxday showed
that the entire MRRJ has presented values that can cause major rainfall.
The Rday index proved to be a promising indicator of rainfall hazards,
which is more effective than those normally used that are only based on
quantity (mm) and/or intensity (mm.h-1) of the rain.