Soil erosion due to rainfall and the impacts of climate change in an Andean highland in Colombia

Abstract

Trends and median slope of daily rainfall that can affect rainfall aggressiveness and cause erosion in the Bogotá - Duitama corridor were studied. For this, the daily records of 26 stations (35 years, from 1980 to 2014) were evaluated, using the Sen's statistic and the Mann-Kendall test with confidence levels higher than 90%. The studied area covered about 8,100 km2, located between 2,100 and 3,300 m a.s.l. in the Colombian Andes. Four stations with positive trends in median annual rainfall were found (from 6.90 mm/year to 28.80 mm/year) and one station with a decrease in median rainfall of -6.86 mm/year. In order to analyze the pluvial aggressiveness as the main agent of soil erosion, the Modified Fournier Indices (MFI) were generated for periods of 10 days. With the maximum decadal Modified Fournier Indices (MFIdmax) of each year, it was possible to establish the median positive trend (Sen) of rainfall aggressiveness in five stations and three stations with negative trends. Through the correlation between the degree of erosion with the square of the decadal average maximum values of each year (MFIdmax2) and the negative annual precipitation, a coefficient of determination (R2) greater than 0.50 was found. The validation of MFIdmax2 to explain the degree of soil erosion is a new useful methodology for land use planning and monitoring. In this way, developing countries have the possibility of using a tool to face the processes of pluvial erosion, vulnerability and adaptation to climate change.