Research Articles (Earth Sciences)

Permanent URI for this collectionhttps://hdl.handle.net/10566/273

Browse

Now showing 1 - 20 of 360

Evaluating satellite-derived evapotranspiration estimates against ground-based measurements in arid upper orange catchment, South Africa
(Taylor and Francis Ltd., 2026) Dube , Timothy; Maxala , Boitumelo; Maswanganye , Eugene
Evapotranspiration (ET) accounts for ~60% of surface water loss, and accurate estimation is vital for water management in arid regions. This study assessed ET in the Upper Orange catchment, South Africa, using the surface energy balance system (SEBS), Penman–Monteith (PM) and MODIS 16 against eddy covariance (EC) flux tower data. Landsat 8 and MODIS were analyzed for eight days in 2020. Model accuracy was evaluated using RMSE, Pbias and R², while ANOVA was used to test differences across land cover types. SEBS showed the highest accuracy (RMSE = 2.48 mm/day, R² = 0.71), outperforming MODIS (RMSE = 3.21 mm/day, R² = 0.59), while PM performed moderately well (RMSE = 2.85 mm/day, R² = 0.66). Both SEBS and PM overestimated ET by 25%–33%. ANOVA confirmed significant land cover differences (p = 0.04), with grasslands recording the highest ET. Overall, SEBS provided robust and spatially reliable estimates, offering valuable insights for water accounting and policy development
Effect of sowing date and genotype on pearl millet yield across semi-arid regions of Sub-Saharan Africa
(John Wiley and Sons Inc, 2026) Dube , Timothy; Awala , Simon; Niipele , Johanna
In climate change–vulnerable, food-insecure semi-arid regions of Sub-Saharan Africa, limited studies compared the performance of pearl millet [Pennisetum glaucum (L.)] landraces and improved genotypes under staggered sowing to establish their interactions, resulting in a generalization that landraces are lower yielding than their improved counterparts. A 3-year field experiment was conducted to compare grain and biomass production of an improved Okashana-2 and the landrace Kantana pearl millet genotypes under five sowing dates between January 1 and March 1 in semi-arid North-Central Namibia. Across years, Kantana sown on January 1 produced the highest grain and shoot biomass yields, ranging from 0.5 to 9.5 t ha−1 and 2.6 to 31.4 t ha−1, respectively, with both gradually declining with sowing delays. Higher grain and biomass yields in early-sown Kantana were due to its longer vegetative growth phase, nearly 2 weeks longer than that of its Okashana-2 counterpart, allowing more time for normal growth and development before heading. Okashana-2, on the other hand, attained its highest yields under January 1 or January 15 sowing dates, with grain and biomass yields ranging from 0.8 to 7.4 t ha−1 and 1.7 to 18.6 t ha−1, respectively, fluctuating among sowing dates; however, March 1 sowing produced the lowest yields. The variable yields for Okashana-2 indicate the genotype’s ability to respond rapidly to soil moisture from various rainfall events. These results demonstrate that maximum pearl millet yields in northern Namibia are achievable by sowing Kantana by January 1, while Okashana-2 has higher and relatively stable yields under late sowing. However, farmers must promptly acquire production inputs and services to facilitate early sowing
A new methodological framework for the determination of water resource classes and resource quality objectives: A case study for the Mzimvubu to Tsitsikamma water management area 7 (WMA7)
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Mulangaphuma, Lawrence Humbulani; Jovanovic, Nebo
The current paper determined water resource classes and Resource Quality Objectives (RQOs) for significant water resources in the Mzimvubu to Tsitsikamma Water Management Area 7 (WMA7) to facilitate sustainable use of the water resources while maintaining ecological integrity. A novel stepwise quantitative and qualitative method was developed to ensure water resource protection in the study area. The methodological approach is proposed as a model framework that could be adopted as guideline and transferable to other catchments in the implementation of Resource Directed Measures (RDMs). The method used water quality and quality components of water resources to determine the classes and RQOs. The study’s major findings were that nineteen Integrated Units of Analysis (IUAs) were delineated, and ninety-five Resource Units were identified and prioritized for both surface and groundwater. Driving water quality variables (nutrients, electrical conductivity, and Escherichia coli) were observed and primary water users (irrigation, settlements, and wastewater treatment works) were identified per Integrated Units of Analysis. Five water resource scenarios were developed and evaluated to capture a likely water resource condition for the present and future. The scenario analysis showed impact is expected under any of the operational scenarios assessed at selected reaches. The water resource classes were determined, with eleven IUAs classified as Class lll, seven IUAs as Class ll, and one IUA as Class l. Water quality and quantity RQOs were set to ensure that both river and groundwater resources are compliant and protected. Therefore, the study recommends that this methodological framework, where classes and RQOs were determined, needs to be implemented and tested.
Land use land cover classification in Japanese wetland and agricultural landscapes via machine learning and multi-source sentinel data
(Taylor and Francis Ltd, 2025) Dube, Timothy; Pandit, Santa; Oki, Kazuo
This study assessed land use and land cover (LULC) in the Oze wetland and Hatase agricultural fields using Random Forest (RF) and Support Vector Machine (SVM). Sentinel-1 Synthetic Aperture Radar (SAR) and Sentinel-2 optical data from 2023–2024 were processed into seasonal median composites. Input features included SAR backscatter coefficients (vertical transmit–vertical receive, vertical transmit–horizontal receive, and their ratio), Sentinel-2 bands (10 m resolution), and vegetation indices: Normalized Difference Vegetation Index (NDVI), Normalized Difference Built-up Index (NDBI), Bare Soil Index (BSI), and Modified Normalized Difference Water Index (MNDWI). Training and testing data were derived from high-resolution PlanetScope and drone imagery. Models were implemented in Python (Google Colab). Results showed RF consistently outperformed SVM, achieving kappa scores of 81%–83% in Oze and 79%–81% in Hatase, while SVM failed to exceed 80%. RF’s robustness for seasonal LULC mapping highlights its potential to support monitoring and sustainable land management in cloud-prone wetland–agriculture systems.
Evaluation of hydro-geomorphic controls on the spatial distribution of sediment-associated phosphorus concentrations in a semi-arid floodplain
(Springer Science and Business Media B.V., 2025) Grenfell, Michael Cyril; Askew, Stephanie M.; Munch, Zahn
Floodplain wetlands are valued for providing ecosystem services, yet these services are threatened due to land-use pressures and climate change. Further, regulating ecosystem services such as phosphorus (P) assimilation and storage are influenced by floodplain morphology and water and sediment dispersal processes, which vary over time. To investigate the influence of hydro-geomorphic processes on total sediment-associated P in surface sediment, this study evaluated the surface inundation and sedimentary characteristics of different regions of a spatially complex semi-arid floodplain in South Africa. Data collection involved stratified floodplain surface sediment sampling to characterise surface variations in geochemistry, particle size and organic matter content. This was paired with a Sentinel-2 imagery-derived frequency of inundation and a LiDAR DEM to incorporate both the influence of hydro-geomorphology and sedimentology on sediment dispersal dynamics and P sequestration on the floodplain. P in surface sediment was strongly affiliated with organic content, Fe, Al and mean particle size. PCA revealed that sample variability was associated with sediment geochemistry and particle size (component one, 63.48% of variance explained) and frequency of inundation and distance to continuous channel (component two, 15.19% of variance explained). An analysis of geomorphic units within the floodplain found that the incomplete avulsion and resultant crevasse splay, as well as abandoned channels, were hotspots of P in surface sediment. However, the spatial extent of other features, with moderate concentrations of P in surface sediment, highlights the importance of geomorphic diversity in overall ecosystem service provision.
Desktop-based determination of first derivative environmental flow requirements for the Luvuvhu headwater sub-basins in South Africa
(Taylor and Francis Ltd, 2026) Kapangaziwiri, Evison; Gumbo, Anesu D.; Mugari, Ephias
This study assessed environmental flow requirements (EFRs) in the Luvuvhu River headwaters, South Africa, using two automated Department of Water and Sanitation monitored stations, A91AB_Out and A91CD_Out. The Revised Desktop Reserve Model (RDRM), supported by participatory mapping and sensitivity analysis, revealed strong hydrological alteration, particularly at A91AB_Out below Albasini Reservoir, where flows deviate from natural conditions. Required EFRs were 17.21 m3 × 106 (52.7% of MAR) at A91AB_Out and 41.03 m3 × 106 (34.6% of MAR) at A91CD_Out, yet observed flows fell below these thresholds during the dry season. Community insights highlighted the importance of avoiding abstraction, addressing wetland degradation, and improving water governance. Sensitivity tests on baseflow (α = 0.96; β = 0.44), flow thresholds (20th percentile), and hydraulic scaling (0.5) enhanced model robustness. The study recommends seasonally timed reservoir releases to restore sediment transport, channel connectivity, aquatic habitats, and rural water supply through community-led, adaptive flow management in data-scarce catchments.
Abandonment integrity assessment regarding legacy oil and gas wells and the effects of associated stray gas leakage on the adjacent shallow aquifer in the karoo basin, South Africa
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Kanyerere, Thokozani Olex B.; Xu, Yongxin; Mugivhi, Murendeni
Shale gas extraction is underway in the Karoo Basin. Previous oil and gas explorers abandoned several wells, and the abandonment statuses of these wells are unknown. Critically, improperly abandoned wells can provide a pathway for the leakage of stray gas into shallow aquifers and degrade water quality. To understand the abandonment integrity risk posed by these wells, a qualitative risk model was developed to assess the likelihood of well-barrier failure leading to a potential leak. The potential leak paths identified include zones with cement losses during grouting, casing corrosion, cement channels, failure to case and cement risk zones, uncased and uncemented sources, uncemented annuli, and unplugged wells. To confirm whether these wells are leaking, geochemical tracing of stray gas was integrated. Eleven of the fifty samples collected had dissolved hydrocarbon gas concentrations that were high enough to use isotopic analysis to determine the source. The results revealed microbial gas via fermentation and carbon dioxide reduction, thermogenic gas, and geothermal gas, as evidenced by larger δ13C1 values and isotopic reversals associated with dolerite intrusions. The thermogenic-type gas detected in legacy abandoned wells and <1 km water boreholes adjacent to these wells serves as evidence that the downhole plugs did not maintain their integrity or were improperly plugged, whereas the thermogenic gas detected in >1 km water boreholes indicates leakage contamination due to natural fracture pathways. The presence of thermogenic gas in legacy wells and in groundwater boreholes <1 km from legacy wells implies that shale gas extraction using hydraulic fracturing cannot be supported in these situations. However, using safety buffer zones greater than 1 km from the legacy wells for shale gas drilling could be supported.
A metasedimentary outlier of the laurentian continental margin preserved on the tonian loch ness supergroup, scottish caledonides
(Geological Society of London, 2025) Frei, Dirk; Rob Strachan, Robin A; Prave, Anthony R
The identification of orogenic unconformities in the high-grade internal zones of orogens requires a multidisciplinary approach. In the northern Scottish Caledonides, isolated occurrences of marble and schist (some kyanite-bearing) do not appear to be integral to the Tonian Loch Ness Supergroup and their affinities are controversial. At Glen Urquhart, structural evidence rules out an allochthonous setting for a kyanite schist-marble succession. Petrological evidence indicates contrasting peak metamorphic conditions between kyanite schist (7-8 kbar and 650°C) and adjacent Tonian paragneiss (9 kbar and 700°C). The U-Pb ages obtained from the youngest detrital zircons within a kyanite schist yield a maximum depositional age of c. 728 Ma, overlapping the c. 725 Ma age of migmatisation of the paragneiss. The schist-paragneiss contact is thus interpreted as a tectonically modified unconformity. C-O isotope data from associated marbles and other marble occurrences across the Loch Ness Supergroup suggest correlation with marbles of the late-Cryogenian Easdale Subgroup (Dalradian Supergroup) east of the Great Glen Fault. Deposition of lower parts of the Dalradian Supergroup was likely restricted to east of the fault, but the basin widened so that younger strata progressively onlapped northwestward and were deposited unconformably on Tonian migmatitic basement.
Geology and geochronology of the Ubendian belt in Malawi; whither the Nyika Terrane
(Elsevier Ltd, 2026) Frei, Dirk; Thomas, Robert .J; Fullgraf, Thomas
The Palaeoproterozoic Ubendian Domain in Malawi comprises the SE segments of three distinct crustal blocks, namely (from north to south) the Mbozi, Ufipa and Nyika subdomains, apparently confirming the historic crustal subdivisions. Together, they represent about 30 % of the surface area of the entire Ubendian belt, most of which lies in Tanzania. We describe their geology and present 14 new U-Pb zircon dates of representative samples. The Mbozi Subdomain (SD) is predominantly comprised of mafic gneisses (Mbozi Group) with no Palaeoproterozoic granitoid intrusions. The Ufipa SD comprises several units of high grade supracrustal gneisses (Ufipa Group), with a maximum depositional age of ∼1990 Ma, deposited upon an interfoliated “cryptic” tonalite-granodiorite orthogneiss basement dated at ∼2150 Ma and occurring as scattered remnants within the paragneisses. Minor post-Ufipa Group granitoids were emplaced at 1990 Ma. The Nyika SD contains sequences of supracrustal gneiss (Nyika Group) deposited between ∼2100 and 1990 Ma, probably during at least two phases of sedimentation. There are numerous granitoids of varying compositions with an overlapping continuum of emplacement ages from ∼2045 to 1946 Ma, some of which are coeval with Nyika Group deposition. The youngest (post-tectonic) granites intrude the Nyika Group, but the status of the older foliated granitoids is less clear due to poor exposure.
Detection of fall armyworm infestation in maize fields during vegetative growth stages using temporal sentinel-2
(Elsevier, 2025) Dzurume, Tatenda; Dube, Timothy; Darvishzadeh, Roshanak
Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), poses a significant risk to global food and income security by attacking various crops, particularly maize. Early detection and management of FAW infestation are crucial for mitigating its impact on crop yields. This study investigated the effect of FAW infestation on the spectral signature of maize fields and classified infestation severity in Bangladesh using Sentinel-2 satellite imagery and Random Forest (RF) classification. Field observations on FAW infestation severity (none, moderate, and severe), collected by the Bangladesh Department of Agricultural Extension during 2019 and 2020, were used to train the RF classifier. Six thousand nine hundred ninety-eight observations were collected from 579 maize fields through weekly scouting. The Kruskal-Wallis test and Dunn's post-hoc test were applied to identify the most significant spectral bands (P < 0.05) for detecting FAW incidence and severity across different maize growth stages. The results demonstrated that the spectral reflectance from Sentinel-2 bands varied significantly among different classes of FAW infestation, with noticeable differences observed during the early developmental stages of maize (vegetative growth stages 3 to 8). RF identified nine spectral bands and two spectral vegetation indices as important for FAW infestation discrimination. The RF classifier was evaluated using five-fold cross-validation, achieving an overall accuracy between 74 % and 84 %. The independent test set's accuracy ranged from 72 % to 82 %. The mean multiclass AUC ranged from 0.83 to 0.95. Moreover, the results demonstrated the feasibility of detecting the severity of FAW infestation using temporal Sentinel-2 data and machine learning techniques. These findings underscore the potential of remote sensing and machine learning techniques for effectively monitoring and managing crop pests. The study provides valuable insights for classifying FAW infestation using high-resolution multitemporal data.
Source area reconstruction using heavy mineral, mineral chemical, geochronological and palaeocurrent data: carboniferous sandstones of the Scottish midland valley
(Elsevier B.V., 2026) Frei, Dirk; Morton, Andrew Clifford; Chisholm, Ian
Integration of several data sets (heavy mineral analysis, rutile and apatite trace element geochemistry, zircon, rutile and apatite geochronology, and palaeocurrent measurements), in conjunction with published sedimentological and petrographic data, has enabled a reconstruction of source areas supplying Late Devonian and Carboniferous sandstones in the eastern part of the Scottish Midland Valley. There is evidence for both first-cycle and recycled detrital sources, and for temporal variations in sediment supply patterns. These temporal shifts in provenance have enabled the succession to be divided into six units of different character (Packages 1 to 6). Late Devonian sandstones (Package 1) have comparable characteristics to Lower Palaeozoic sandstones of the Scottish Southern Uplands Block to the south, and are interpreted as recycled from similar material. Differences in apatite morphology testify to a shift from aeolian deposition in the Knox Pulpit Formation to fluvial deposition in the overlying Kinnesswood Formation. A recycled source is also inferred for the overlying Strathclyde Group (Visean) sandstones (Package 2), on the basis of depletion of weatherable mineral components, but palaeocurrent evidence and mineral chemical data indicate a change in source area location and sediment input direction. Recycling from an Upper Old Red Sandstone source (Late Devonian) in the Moray Firth to the north is considered most likely. Input from a more distant northern source, delivered by the ‘Pennine River' appears in the later part of Package 2, and becomes dominant at the base of the Limestone Coal Formation (Namurian) (Package 3). The Pennine River was a large fluvial system that is known to have supplied much of the Carboniferous succession in the Pennine Basin of Yorkshire and Northumberland. The new rutile trace element and geochronological data acquired in this study confirm that the source region included parts of East Greenland where high-grade (granulite facies) metapelites formed during the Caledonian orogenic cycle are located.
The potential for urban agriculture (UA) in Cape Town, South Africa: a suitability analysis
(Taylor and Francis Ltd, 2025) Kanosvamhira, Tinashe Paul; Musasa, Tatenda; Mupepi, Oshneck
Urban agriculture plays a pivotal role in enhancing human well-being by contributing to food security, economic prosperity, and environmental sustainability. Despite its significance, many cities lack accurate inventories to identify suitable sites for such initiatives. This study examines the potential for urban agriculture in Cape Town using Multi-Criteria Decision Making techniques. Factors such as temperature, soil fertility, road accessibility, and precipitation were analysed using weighted overlay to determine the agricultural potential in Cape Town. Utilizing methodologies like the Analytic Hierarchy Process and Weighted Linear Combination, the agricultural potential was established. Findings indicate that there are highly suitable areas for agriculture whose potential has not yet been fully exploited. Currently, agricultural activities like vineyards, crop production, and cattle farming, though situated on good agricultural land, are not as prominent despite the availability of vast tracts of highly suitable land. Therefore, there is a need to raise awareness and promote urban agriculture to alleviate poverty-related food insecurities. The implementation of urban agriculture is anticipated to significantly improve food security, create economic opportunities, and enhance environmental sustainability within urban areas. The study recommends the need for longitudinal studies to gather essential information for informed decision-making, ensuring the sustainability of urban agriculture initiatives.
Evaluation of carbon dioxide storage potential in wells of the Bredasdorp Basin offshore South Africa
(Taylor and Francis Ltd, 2025) Ngcobo, Luyanda; Afolayan, Blessing Ayotomiwa; Opuwari, Mimonitu
This study focuses on determining how carbon dioxide (CO2) storage can be stored in the central Bredasdorp basin offshore South Africa. Logs, seismic lines, and reports of three exploration wells were used to build a 3D static model, and the compressibility method was used to estimate the CO2 static storage capacity of the reservoir. The wells displayed fair to good porosity and moderate permeability. The zone of interest had little to no faulting, and there is evidence of differential deposition of marine sandstones that overlie fluvial shales. The sandstones have good reservoir characteristics and are overlain by thick shales that serve as seals. The reservoir displayed thinning in the eastern direction and over structural highs. A static storage assessment of the reservoir showed 0.64 Mt of CO2, and the effect of changing pore volume and water saturation on overall CO2 storage volume was observed. The results revealed that an increase in pore volume would also increase the amount of CO2 stored in the reservoir. Conversely, increased water saturation leads to decreased CO2 that can be stored in the reservoir. This study has shown that the pre-existing reservoir fluid has an impact on CO2 storage volume; the greater the volume of water in the reservoir, the less the volume of CO2 that can be stored in the reservoir; this is because water is less compressible than rock, oil or gas
Application of change detection techniques driven by expert opinions for small-area studies in developing countries
(Elsevier B.V., 2025) Kapangaziwiri, Evison; Mbendana, Tanaka A; Gumbo, Anesu D.
Rapid urbanisation in developing countries, fuelled by population growth and rural-to-urban migration, poses significant challenges for service delivery in under-resourced municipalities. Dangamvura Township in Mutare, Zimbabwe, exemplifies this issue, potentially overwhelming the City of Mutare services. Resource limitations have hindered the quantification of these changes. This study assesses changes in land use and land cover (LULC) in Dangamvura Township, Mutare, Zimbabwe, between 2010 and 2022, using stakeholder-driven methods, Google Earth Pro (GEP) and machine learning in R. A four-tier methodology was applied integrating R and expert validation through GEP to classify and quantify changes in LULC. The analysis identified built-up areas, cropland, and bare land as the main LULC classes. The results from R showed that built-up areas expanded from 3.74 km² in 2010 to 8.64 km² in 2022, the bare land decreased from 3.10 km² to 1.42 km², and the cropland declined from 6.06 km² to 2.84 km². GEP assessments indicated an increase in built-up areas from 5.08 km² to 8.91 km², a reduction in bare land from 3.57 km² to 1.97 km², and a decrease in cropland from 4.25 km² to 2.02 km² over the same period. These findings highlight significant urban expansion and declining agricultural and undeveloped land. The disparities between the R statistical software and the GEP results underscore the importance of integrating expert opinions to validate classifications, particularly in small-area studies with spatial heterogeneity. The results provide valuable insights for urban planning and decision-making, highlighting the need for adaptive strategies to manage urban growth and infrastructure development. The tiered methodology demonstrates the potential of combining advanced remote sensing tools with local knowledge to achieve robust LULC assessments in resource-limited settings, guiding sustainable urban planning and informing policy interventions to address challenges associated with rapid urbanisation in resource-limited countries.
Cloud-based big data analytics for monitoring invasive plants in groundwater-dependent ecosystems of Nuwejaars catchment, South Africa
(Elsevier B.V., 2026) Moropane, Mmasechaba L; Dube, Timothy; Mazvimavi, Dominic
Groundwater-dependent ecosystems (GDEs) provide crucial ecological and hydrological stability but are increasingly threatened by groundwater-dependent invasive plants (GDIPs), particularly in regions with limited water resources. Although GDEs have been widely studied, long-term quantitative assessments of how invasive plants alter these ecosystems remain limited. Hence, this study evaluated the impacts of invasive plants within the GDEs of the Nuwejaars Catchment, South Africa, by monitoring their spatial and temporal dynamics and quantifying the extent to which they displace native plants. Landsat-8 imagery, a Random Forest classifier, and Explainable Artificial Intelligence (XAI) techniques were integrated to map and quantify the annual distribution of GDIPs over a 12-year period. XAI interpretability techniques including SHapley Additive exPlanations (SHAP), partial dependence plots (PDPs), and recursive feature elimination (RFECV) were applied to identify key environmental conditions influencing GDIP occurrence. Spatial-temporal analysis revealed that GDIPs expanded from 40.9 % (1060 ha) in 2013 to 63.9 % (1660 ha) in 2024, displacing large areas of native fynbos vegetation. Inter-annual change analysis showed accelerated GDIP growth following the extreme 2015–2018 drought, which reduced groundwater availability for native species with shallow roots. Elevation, slope, and moisture vegetation indices emerged as the most influential predictors for classification, with PDPs revealing that GDIPs favoured lower elevations and steep slopes. Classification accuracy improved over time, with F1-Scores and overall accuracies ranging between 68.4 % to 82.5 % from 2013 to 2024. Overall, these findings highlight the persistent spread of GDIPs and their potential to transform GDEs in semi-arid areas. This study demonstrates the value of integrating remote sensing and interpretable machine learning to support ecological monitoring and targeted invasive species management.
Optical dating of Holocene extreme flood events in eastern South Africa and their connection to ENSO variability
(Elsevier Ltd, 2026) Grenfell, Michael C; Wood, Jamie C; Toms, Phillip S
Existing research examining tributary blocked-valley lake and wetland development upon the Mfolozi River floodplain (South African east coast) has highlighted the potential for blocked-valley lakes to act as mainstem palaeoflood archives. Sand and silt units preserved within the organic deposits of these floodplain-impounded features represent relatively large flood events and provide an opportunity to establish the frequency of extreme flooding in the region beyond the timespan of instrumental and historical records, thereby helping to reduce uncertainty around future tropical cyclone activity in a warming world. However, absolute age estimates for these sequences have been limited to radiocarbon dating of organic units, restricting flood history reconstruction. This study had two inter-related aims. Firstly, to evaluate the use of optically stimulated luminescence (OSL) dating for chronicling clastic sediments associated with the floodplain's blocked-valley lakes. Secondly, in combination with radiocarbon dating and Bayesian age-depth modelling, to reconstruct flood history across three sites on the Mfolozi floodplain and investigate the climatic factors that drove past extreme flooding in the region. The Finite Mixture Model (FMM) applied to single grain OSL data was identified as the most suitable equivalent dose (De) model, producing age estimates that either aligned with historical records and/or accounted for the largest population of grains with a common dose. The deposition models developed provide evidence for the occurrence of multiple extreme floods since the first event identified at 7.2 ka, providing the first long-term flood record for the region. Comparison of the Mfolozi palaeoflood record with independent sedimentary hydroclimatic evidence from the region indicates a historical tendency for more frequent extreme floods during weakened El Niño conditions (i.e., La Niña or neutral ENSO phases). This suggests that variations in ENSO conditions through the mid-to-late Holocene likely played a fundamental role in triggering extreme flooding along South Africa's east coast.
Macroinvertebrate diversity within pan wetlands in relation to geological type and hydroperiod in a protected subtropical Austral national park
(Taylor & Francis Ltd., 2025) Dube, Timothy; Leshaba, Elsie N; Dondofema, Farai
Despite their small size, wetland pan systems play a crucial role as habitats for diverse aquatic biota. Macroinvertebrate diversity across 12 pan wetlands in relation to geological type (i.e. sandstone, granite, basalt and rhyolite) and hydroperiod (i.e. high, low) in a protected subtropical national park in South Africa was studied. Water temperature, pH, TDS, conductivity, phosphates and salinity showed significant differences among hydroperiods, with significant differences among geological types being observed for water temperature and ammonium. Most of the sediment variables were found to be significant across hydroperiods and geological types. 5145 macroinvertebrate individuals belonging to 41 genera and 9 orders were identified. Macroinvertebrates were diverse during the high hydroperiod and abundant during the low hydroperiod. The canonical correspondence analysis explained 35.8% of the fitted cumulative variation in the macroinvertebrate community structure and environmental variables across different hydroperiods and geological types. This study aimed to provide a better understanding of how they are influenced by a pan geological type and hydroperiod, and this information is crucial as it aids in providing management options for refuge aquatic taxa in a protected area and for the protection of these wetlands
The potential for urban agriculture (UA) in Cape Town, South Africa: a suitability analysis
(Taylor and Francis Ltd., 2025) Musasa, Tatenda; Kanosvamhira, Tinashe P; Mupepi, Oshneck
Urban agriculture plays a pivotal role in enhancing human well-being by contributing to food security, economic prosperity, and environmental sustainability. Despite its significance, many cities lack accurate inventories to identify suitable sites for such initiatives. This study examines the potential for urban agriculture in Cape Town using Multi-Criteria Decision Making techniques. Factors such as temperature, soil fertility, road accessibility, and precipitation were analysed using weighted overlay to determine the agricultural potential in Cape Town. Utilizing methodologies like the Analytic Hierarchy Process and Weighted Linear Combination, the agricultural potential was established. Findings indicate that there are highly suitable areas for agriculture whose potential has not yet been fully exploited. Currently, agricultural activities like vineyards, crop production, and cattle farming, though situated on good agricultural land, are not as prominent despite the availability of vast tracts of highly suitable land. Therefore, there is a need to raise awareness and promote urban agriculture to alleviate poverty-related food insecurities. The implementation of urban agriculture is anticipated to significantly improve food security, create economic opportunities, and enhance environmental sustainability within urban areas. The study recommends the need for longitudinal studies to gather essential information for informed decision-making, ensuring the sustainability of urban agriculture initiatives.
Personal factors influencing emergency evacuation decisions under different flash flood characteristics
(Springer Science and Business Media B.V., 2025) Liu, Dedi; Xu, Yongxin; Zhang, Ruikang
Emergency evacuation has received more attention as an effective tool of flash flood disaster prevention that calls for systematic thinking rooted in natural and social sciences. Although personal factors influencing emergency evacuation decisions (EED) after receiving a flood warning have been widely discussed, few studies have referred this issue to the flash flood characteristics. This study explored the personal factors influencing EED under different flash flood characteristics (i.e., the frequency, occurrence time, and severity of flash floods) through field survey data. Three typical flash flood characteristics in three towns were selected as case studies. An ordinary logistical model and path analysis were used to analyze the independent influence and influence process of the personal factors on evacuation intention under the three flash flood characteristics. The results showed that personalized risk perception and warning type consistently influenced evacuation intention regardless of the flash flood characteristics, while the independent influence of flood experience and reliance on hazard information on evacuation intention was varied with the flash flood characteristics. Perceived exposure influenced evacuation intention through the mediations of flood experience when there were high-frequency, recent, and loss-causing flash floods, and of risk perception when there were low-frequency, distant, and few-loss-causing flash floods. The effect of warning type on evacuation intention was varied with the flash flood characteristics if the warning type changed from the suggestive rainstorm red warning to mandatory ready-to-evacuate warning. However, if the warning type changed from the ready-to-evacuate to immediate-evacuation warning, there was no significant difference in this effect regardless of the flash flood characteristics. Therefore, it is necessary to implement distinctive emergency management according to specific flash flood characteristics.
Wetland inundation and moisture dynamics in Tugwi-Zibagwe and Shashe sub-catchments, Zimbabwe: insights from 2017 to 2023
(Taylor and Francis Ltd., 2025) Dube, Timothy; Mupepi, Oshneck; Marambanyika, Thomas
We analysed the Modified Normalized Difference Water Index (MNDWI) from Sentinel-2 Level 1 C and the Topographic Wetness Index (TWI) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation model (DEM). Total inundated wetland area dropped by 0.1% in the Tugwi-Zibagwe and by 0.2% in the Shashe between 2017 and 2023. Significant correlations between temperature and rainfall impacts were observed in the Shashe sub-catchment (r = −0.84; p = .02 and r = 0.77; p = .04), whereas in Tugwi-Zibagwe, these correlations were less pronounced (r = −0.60; p = .15 and r = 0.39; p = .39). Between 2017 and 2023, large and small seasonal wetlands fluctuated between 60.2% and 35.9% of the total wetland area in Shashe whilst in Tugwi-Zibagwe it varied from 17.4% to 14.9%. The findings underscore the critical importance of conserving and restoring small (<1 ha) unprotected wetlands in rural semi-arid regions.

Browse

Recent Submissions