Timing is Everything–Drought Classification for Risk Assessment

Drought is one of the most severe natural disasters with a high risk for human livelihoods. Remote sensing based drought indices can identify dry periods using, e.g., precipitation or vegetation information. Besides frequency, duration, and intensity, the timing of a drought onset and duration are important variables to measure the drought impact and risk. This article classifies drought events based on the timing of the drought and with regard to their impact on vegetation production during different crop growing stages. Drought and nondrought seasons are analyzed in Eastern Cape Province, South Africa. Here, the impact of a drought on vegetation production highly depends on the starting point and the duration of rainfall during the growing season. Weighted linear combination was applied based on vulnerable vegetation growing stages in the phenology to classify drought severity per season. Particularly the extreme drought season in 2015/2016 as well as the normal nondrought season in 2011/2012 was emphasized. The developed approach serves as input to quantify drought impact per cropping season from local to regional scales. Integration of socio-economic information can further complement this hazard information to support the quantification of the actual drought risk.