Hydrodynamic Modelling of Floods and Estimating Socio‑economic Impacts of Floods in Ugandan River Malaba Sub‑catchment
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Date
2022
Journal Title
Journal ISSN
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Publisher
Earth Systems and Environment
Abstract
River Malaba sub-catchment tends to experience dramatic flooding events, with several socio-economic impacts to the
nearby communities, such as loss of lives and destructions of physical infrastructure. Analysis of spatiotemporal extents
to which settlements, crops and physical infrastructures tend to be inundated are vital for predictive planning of risk-based
adaptation measures. This paper presents a case study on flood risk assessment for Ugandan River Malaba sub-catchment.
We applied the two-dimensional Hydraulic Engineering Center’s River Analysis System (2D HEC-RAS) for modelling of
flooding extents. We considered extreme flow quantiles, lower and upper quantiles corresponding to the 95% confidence
interval limits aimed at determining uncertainties in the flooding extents. Spatial extents of inundation on human settlement,
land cover and infrastructure were analysed with respect to return periods of extreme flow quantiles. Finally, we estimated
economic loss on infrastructure due to flooding. Results from the 2D HEC-RAS model were satisfactorily comparable with
the results of observations. Amongst the land use types, cropland exhibited the highest vulnerability with at least 10,234.8
hectare (ha) susceptible to flooding event of 100-year return period (YRP). Inundated built-up land-use exhibited the highest
vulnerability percentage increase (90%) between 2- and 100-YRP. In US Dollar, about US$ 33 million and US$ 39 million
losses are estimated at 2- and 100-YRP, respectively, due to inundated rice gardens and these indicate a looming high risk
of household food insecurity and poverty. Several infrastructure including 15 academic institutions, 12 health facilities, 32
worshiping places remain annually vulnerable to flooding. At least 6 km and 7 km of road network are also susceptible to
flooding under extreme flows of return periods 2 and 100 years, respectively. Churches exhibited the highest economic losses
of US$ 855,065 and US$ 1,623,832 at 2-YRP and 100-YRP, respectively. This study findings are relevant for planning the
development of sustainable flood risk adaptation pathways given the established destructions within the sub-catchment due
to flooding.
Description
Keywords
Hydrodynamic modelling, Floods, River Malaba sub-catchment, Vulnerability, 2D HEC-RAS, Flooding impacts
Citation
Mubialiwo, A., Abebe, A., Kawo, N. S., Ekolu, J., Nadarajah, S., & Onyutha, C. (2022). Hydrodynamic modelling of floods and estimating socio-economic impacts of floods in Ugandan River Malaba Sub-catchment. Earth Systems and Environment, 6(1), 45-67. https://doi.org/10.1007/s41748-021-00283-w