Frank Mudenda

This research implemented event-based hydrodynamic modelling techniques to characterise flash flooding in Nangoma catchment. The HEC-RAS 2D hydraulic model was calibrated and validated with acceptable overall statistical objective functions NSE of 84.6%-, R2 at 99% and PBIAS of -2.5%. Representative design hyetographs were derived from the hybrid clustering optimised for four clusters under the Inter-event Time Definition of three hours. The catchment flash flood threshold curve estimated the R2 of 0.96 confirming that the power-law model provided an excellent fit to the flood generating event population capturing 96% of the variance in average intensity as a function of duration across the full range of observed convective events especially under convective storms with 1.2 – 1.5 hours, triggered by corresponding rainfall amounts above 39 mm. To assess possible interventions, five scenarios were simulated for optimal NbS at the respective three monitoring sites (CP1-3) indicated that rainwater harvesting implemented on the main river channel, tributaries, and off-river storage improved water storage while reducing flooding risks by 51% on CP1, 30% on CP2, and 36% at the outlet on CP3. Therefore, such outputs from this integrated approach are key to providing valuable insights and actionable water-resilient nature-based solutions such as rainwater harvesting and enhanced catchment storage for communities facing recurring flash flood challenges.

Rapid urbanization has led to increasing structural modification of river catchments through dam construction and concrete-lining of natural channels as flood management measures. These interventions can alter the natural hydrology. This necessitates assessment of their influence on hydrology at a catchment scale. However, such evaluations are particularly challenging in data-scarce regions such as the Chongwe River Catchment, where hydrometric records capturing conditions before and after structural modifications are limited. Therefore, we applied a 2D rain-on-grid approach in HEC-RAS to evaluate changes in high-flow responses to short-duration, high-intensity rainfall events in the Chongwe River Catchment in Zambia, where structural interventions have been implemented. The terrain was modified in HEC-RAS to represent 21 km of concrete drains and ten dams. Sensitivity analysis conducted on five key model parameters showed that parameters controlling surface runoff generation, particularly curve number, exerted the strongest influence on simulated peak flows, while routing-related parameters had a secondary effect. Model calibration and validation showed strong performance with R² = 0.99, NSE = 0.75 and PBIAS = −0.68% during calibration and R² = 0.95, NSE = 0.75, PBIAS = −2.49% during validation. Four scenarios were simulated to determine the hydrological effects of channel concrete-lining and dams. The results showed that concrete-lining of natural channels in the urban area increased high flows at the main outlet by approximately 4.6%, generated localized instantaneous maximum channel velocities of up to 20 m/s, increased flood depths by up to 11%, decreased lag times and expanded flood inundation widths by up to 15%. The existing dams reduced peak flows by about 28%, increased lag times, reduced flood depths by about 11%, and reduced flood inundation widths by up to 8% across the catchment. The findings demonstrate that enhancing stormwater conveyance through concrete-lining must be complemented by storage to manage high flows, while future work should explore nature-based solutions to reduce channel velocities and improve sustainable flood mitigation. Therefore, the study provides event-scale insights to support flood-risk management and infrastructure planning in rapidly urbanizing, data-scarce catchments.

With accelerating climate change and urbanization, river catchments continue to experience structural modifications through dam construction and concrete-lining of natural channels as adaptation measures. These interventions can alter the natural hydrology. This necessitates assessment of their influence on hydrology at a catchment scale. However, such evaluations are particularly challenging in data-scarce regions such as the Chongwe River Catchment, where hydrometric records capturing conditions before and after structural modifications are limited. Therefore, we applied a 2D rain-on-grid approach in HEC-RAS to evaluate changes in high-flow characteristics in the Chongwe River Catchment in Zambia, where structural interventions have been implemented. The terrain was modified in HEC-RAS to represent 21 km of concrete drains and ten dams. Sensitivity analysis was conducted on five model parameters and showed that Manning’s roughness coefficient had by far the largest impact on peak flows. Model calibration and validation showed strong performance with R² = 0.99, NSE = 0.75 and PBIAS = – 0.68 % during calibration and R² = 0.95, NSE = 0.75, PBIAS = – 2.49 % during validation. Four scenarios were simulated to determine the hydrological effects of channel concrete-lining and dams. The results showed that concrete-lining of natural channels in the urban area increased high flows at the main outlet by approximately 4.6%, generated very high channel velocities of up to 20 m/s, increased flood depths by up to 11%, and expanded flood extents by up to 15%. The existing dams reduced peak flows by about 28%, increased lag times, reduced flood depths by about 11%, and reduced flood extents by up to 8% across the catchment. The findings demonstrate that enhancing stormwater conveyance through concrete-lining must be complemented by storage to manage high flows, while future work should explore nature-based solutions to reduce channel velocities and improve sustainable flood mitigation.

The responses of watershed systems to the dynamics of climate change are complex, requiring analyses of the hydrological cycle before any adaptation solutions are adopted. Despite increasing calls for adaptation, limited information exists on modelling approaches and global datasets to simulate structural and nature-based solutions (NbS). Existing reviews have largely focused on types, benefits, challenges, and comparisons of structural and NbS. Therefore, this review aims to identify modelling approaches and global datasets through a systematic review to support the successive simulations of these solutions. We followed the guidance of the updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) to select 341 studies from DOAJ and Scopus databases for analysis. The review showed a diverse array of hydrological and hydraulic modelling software that can be applied to both categories of solutions, with HEC-RAS, SWAT, and potentially HEC-HMS appearing to offer the best capabilities for integrating structural and NbS. Importantly, while data scarcity emerges as a significant barrier in implementing these models, modellers have access to open-source datasets and tools to effectively implement the models in practical scenarios. This review's findings can enhance real-world watershed management practices by supporting more informed and integrated adaptation strategies through watershed modelling.

Hydropower is a source of renewable energy, which provides clean electricity around the world with lower greenhouse gas emissions than other sources of energy. Zambia's electricity deficit has been increasing in recent years. As of 2019, over 1.9 million households (57.6%) had no access to electricity and over 96% of the rural population are still without electricity. This calls for attention and sustainable solutions to electrification as reinforced by goal number 7 of the sustainable development goals. Such solutions include the development of a Zambian Hydropower Atlas that can showcase the country's hydropower potential including small-scale technologies, which can boost Zambia's electrification by providing green electricity. The aim of this study was to develop a run-of-river evaluation framework for the selection of hydropower potential sites to be included in the Zambian Hydropower Atlas. The data and formulas required to evaluate hydropower potential were identified and evaluated to develop the evaluation process in the Zambian context. The developed evaluation framework was applied to an existing run-of-river hydropower site located in Zambia to show its application, and it estimated the hydropower potential at the site within a deviation of 14%. The developed evaluation framework can give a first-order evaluation of hydropower potential.

Coronavirus disease 2019 (COVID-19) is a respiratory tract infection that emerged from China in December 2019 and is caused by severe acute respiratory syndrome coronavirus 2. Due to the airborne nature of its transmission, COVID-19 spread to the rest of the world rapidly. Thus, the World Health Organization declared COVID-19 a pandemic. This paper evaluated the factors that lead to self-medication in people suffering from respiratory tract infections such as COVID-19, and the consequences of practicing self-medication using antimicrobial agents. Most of the signs and symptoms of COVID-19 are also seen in infections such as malaria, flu, and the common cold. For this reason, and also due to poor healthcare-seeking behaviour, most people tend to self-medicate using medicines that are known to be effective against malaria, common cold, and COVID-19. Among the commonly used medicines in the practice of self-medication include antibacterials, antimalarials, and antivirals. Some vitamins such as vitamin C boost the immune system enabling it to provide effective defence mechanisms against microbes. However, self-medication may pose consequences such as the emergence of antimicrobial-resistant microorganisms, hypersensitivity reactions as well as dose-dependent toxicities viz dermatoxicity, cardiotoxicity, and hepatoxicity. Infectious diseases caused by antimicrobial-resistant microbes are difficult and, in some instances, impossible to treat thereby leading to increased morbidity and mortality among infected people. Consequently, antimicrobial resistance poses another global public health problem and requires a multisectoral approach to curb. It is our recommendation that all governments ensure that there are adequate medicines and efficient human resources in healthcare facilities as well as sufficient public awareness to prevent people from seeking self-medication.