| dc.description.abstract | River Mubuku has been exposed to series of alternating hydrologic droughts and flash floods that
constantly affect the social and economic livelihood of the riparian population within the
catchment and the surrounding communities. Some of the most severe floods and drought events
include; the flash flood of May 2013 that led to displacement of up to 7000 people and massive
destruction of property, facilities like schools, hospitals and other utilities; the flood of May 2020
that affected 120,000 people. Drought has equally had a lion share with 21 drought events out of
35 drought and flood events reported between February 2017 and March 2018, which affects
livelihood of the communities. Additionally, there is a challenge of limited resources, therefore
there is need for identification of the most prone areas, to be considered as priority in floods and
drought mitigation strategies and possible assistance to the would be affected population.
The aim of this study was to model flood and drought risks in River Mubuku so as to provide a
better understanding of their spatial distribution as well as identify hotspot areas. The study
employed Microsoft excel, R-Studio, hydrologic and hydraulics models coupled with GIS tools to
rainfall analysis, flood discharge simulation, drought forecasting and hazard and risks maps. The
results and findings were presented in tables and maps.
HEC-RAS generated flood inundation maps which were subsequently overlaid on the base map of
the study area to produce hazard map which showed 164.1, 175.2, 184.8, 194.0, 201.3 and 207.2
hectare of catchment area are submerged in water on occurrence of 2, 5, 10-, 25-, 50- and 100-
years floods respectively with Kyanya Community, Ruboni community camp, Near Fort Portal
Highway bridge and portion of Nkenda-Bugoye-Nyakalingijo road (from (30°5’10’’E,
0°19’23’’N) to (30°5’’16’’E,0°19’’14’’N) identified as hotspot areas and 0.55%, 27.92%, 52.63%,
18.87% and 0.031% of the total catchment area under very low, low, medium, high and extreme
risks respectively.
In Drought forecasting, the model parameters were checked for significance and all the p-values
were below 0.01 and therefore would adequately predict the scenarios. The model was then
calibrated by checking the RMSE errors which was least for 5 forecasting scenarios and the 3-year
lead time which had the least RMSE of 2.229 and had residuals which followed a normal
distribution was used. The Streamflow Drought Indices model identified several droughts and the
most severe of all being in the months of July in 2022, 2023 and 2024.
The river Mubuku catchment is prone to flash floods with even at lower rainfall intensities of 2
years return period where about 8% of the total catchment area is submerged by more than 5m
depth of water which considered extreme risk according to MLIT(MLIT,2005) flood risk criteria
and a total area of about 80% of area submerged by 100-year return flood at all levels of hazard.
While majority of the catchment (52.63%) experiences medium flood risk, the high elevation areas
near Mountain Rwenzori ranges are less prone compared to low-lying areas that are under extreme
risk and are recommended for immediate attention and assistance in case of floods. The catchment
is equally prone to hydrologic drought with the sub-counties of Maliba and Bugoye had the most
severe drought risks based on socioeconomic and non-socio-economic indicators. | en_US |
