An assessment of rainfall characteristics surrounding flood occurrences in Uganda

Abstract

Floods are one of the most devastating and recurring natural hazards threatening the lives and properties of communities in Uganda. Flood occurrences have increased over parts of Uganda and are attributed to climate change and anthropogenic activities. Rainfall is the key factor behind flood occurrences in Uganda and the world at large, an understanding of the characteristics of rainfall that triggers floods is important for effective monitoring and early warning of flood disasters. However, there is minimal information about the characteristics of flood-triggering rainfall in Uganda. This study examined the rainfall characteristics surrounding floods that occurred during 2003-2015 in Uganda. Information (including date and place of occurrence) on floods that occurred during 2003-2015 were sourced from literature and media. For each of the identified flood events, daily rainfall (from PERSIANNCDR) was analyzed. Cumulative daily rainfall was generated for the day the flood occurred and 5 days prior to the flood occurrence. The purpose of this analysis was to determine the one-day, three-day and five-day cumulative rainfall thresholds surrounding floods in order to identify the thresholds of flood triggering rainfall in Uganda. The results show that rainfall thresholds ranging between 7-19 mm, 20-40 mm and 30-65mm for 1-day, 3-days and 5-days respectively can trigger floods in parts of Uganda. It is also observed that it takes a few mm of cumulative daily rainfall (30-40mm) to trigger a flood in Western Uganda than it does in Eastern Uganda (50-65mm). This implies that with the projected increases in rainfall amounts over Uganda, floods would become even more frequent in Western Uganda.