Representative rainfall thresholds for flash floods in the Cali river watershed, Colombia

Abstract

Abstract. In the 21st century, societies face a significant increase in the number of extreme hydrometeorological events associated with climate variability (CV) and/or climate change (CC). Research has recently focused on establishing adaptation and mitigation measures to counteract the effects of CV and CC, especially those associated with precipitation, such as flash floods and flooding. In this study, 27 floods, listed in the historical database of natural disasters (DesInventar), occurring between 1980 and 2012, were analyzed. Using the daily hydrometeorological data, representative rainfall thresholds were defined to predict flash floods in the hydrographic basin of the Cali River, Colombia. Antecedent rainfall (AR), or short-term rain (1, 3, 5 and 7 days), and accumulated antecedent rainfall (AAR), or long-term rain (5, 7, 10, 15, 20, 25, 30, 60 and 90 days), levels were defined. The analysis showed that the greatest determinant for the occurrence of floods is AAR, with thresholds greater than 73, 95, 124, 170, 218 and 273 mm, for 5, 7, 10, 15, 20 and 25 days, respectively. Additionally, the data showed that, historically, the greatest number of flash floods (81.7 %) occurred in the Cali River basin in the months of April, May, and June.