Characterizing flood occurrence in Nyamwamba river catchment in Kasese District from 1960-2070

Abstract

Floods are the leading cause of fatalities from disasters worldwide and rank among the most common natural hazards, causing significant impacts on lives and property. In 2022, 176 flood events were recorded globally, surpassing the average of 168 incidents per year from 2002 to 2021, with Asia being the most affected region. Uganda, particularly the Kasese district, frequently experiences flooding, with devastating events occurring annually since 2013. The Nyamwamba water catchment, covering 107 km², has faced severe consequences, including loss of life, destruction of property and infrastructure, and community displacement. This study aimed to assess the incidence of flooding in the Nyamwamba River catchment from 1960 to 2070. A cross-sectional approach, utilizing mixed methods for data collection, including qualitative, spatial, and quantitative techniques, was employed to collect data. Qualitative data were gathered from key informants, including technical staff from the Kasese District Local Government and community elders, and site observations along the River Nyamwamba catchment. Secondary quantitative data on climate parameters were sourced from the Department of Meteorology. Flow data was obtained from the Water Resource Monitoring and Assessment Department of the Ministry of Water and Environment. Yet, soil maps were obtained from the Kawanda National Agricultural Research Laboratory. Further literature reviews were conducted to supplement existing knowledge products and enhance the qualitative and quantitative data. Data analysis involved the Standardized Precipitation Index (SPI) and the Hydrologic Engineering Centers River Analysis System (HECRAS), integrated into ArcMap 10.4. SPI was processed in RStudio to project flood incidents for mid-century and end-century scenarios, while thematic content analysis reconstructed lived experiences related to historical flood occurrences. The findings revealed that flooding in the Nyamwamba catchment is a longstanding issue, with significant historical events recorded in years such as 1962, 1964, 1974, 2009, and 2021. Qualitative data indicated that River Nyamwamba experiences annual flooding, though the severity varies. Projections suggest that flooding will likely continue into the mid-century, with changes in the timing of events attributed to climate change. Between 2016 and 2025, Kasese District and the Nyamwamba River experienced a series of severe flooding events. Notable incidents include the April 2016, May 2017, May 2020, 2022, and 2023 floods, which caused further household displacements, infrastructural damage, and economic hardship for the affected communities and the Kasese District.

Subject Keywords: Floods, Flood incidences, Spatio-Temporal, River Nyamwamba water catchment, Standardized Precipitation Index (SPI) and the Hydrologic Engineering Centers River Analysis System (HECRAS).