Spatio-temporal Assessment of Soil Erosion Risk in the Tono River Basin, Upper East Ghana, using the RUSLE Model

2026-02-03T08:04:10+00:00

This study presents a comprehensive assessment of soil erosion dynamics in the Tono River Basin, Upper East Ghana, from 2017 to 2024, employing the Revised Universal Soil Loss Equation (RUSLE) in combination with geospatial technologies and statistical analysis. The research reveals a dramatic 217.1% increase in mean soil erosion rates, escalating from 0.85t/ha/yr to 2.68t/ha/yr, with total annual soil loss surging from 8.27 to 26.24 million tons. Spatial analysis demonstrated significant clustering of erosion patterns, with Global Moran's I increasing from 0.189 to 0.259, indicating strengthened spatial organization of erosion hotspots over time. Land use change analysis revealed complex erosion responses, including a paradoxical 244.1% erosion increase in the expansion of forested areas (131.9% growth) and an extraordinary 5,023.7% erosion escalation in fragmented flooded vegetation zones. The study identified persistent erosion hotspots covering 24.3% of the basin, alongside emerging hotspots (10.8%) and recovered areas (10.2%). Factor correlation analysis showed topography (LS factor) as the primary control (r = 0.756), while vegetation cover factors substantially increased in importance. The findings underscore the critical need for targeted conservation strategies to address the specific erosion processes and the identified spatial patterns, to provide a scientific foundation for sustainable land management in semi-arid watersheds experiencing rapid environmental change.

Dynamics of Urban Sprawl in Dar es Salaam: a Three-decade Analysis using Remote Sensing and Landscape Metrics

2026-02-03T08:11:02+00:00

Dar es Salaam, the largest city in Tanzania, has undergone rapid population growth over recent decades. This surge in population has been accompanied by inadequate enforcement of urban planning regulations. The combination of these factors has led to extensive urban sprawl with far-reaching environmental and socio-economic consequences. Environmentally, the unchecked spread of the city has contributed to the loss of natural habitats, increased flooding risk, heat stress, and the degradation of vital ecosystems. Socio-economically, urban sprawl has placed considerable strain on public infrastructure, reduced access to essential services, and exacerbated inequalities within the city. Overall, the lack of effective planning has intensified the challenges associated with rapid urbanisation in Dar es Salaam.

This study integrated remote sensing and landscape metrics to assess urban sprawl dynamics over three decades (1995–2024). Thereby, it sought to highlight the phenomenon of peri-urban expansion and its associated risks (e.g., flooding, heat stress, and vegetation loss). Multi-temporal Landsat imagery was processed by using the random forest supervised classification, accuracy assessment, and post-classification change detection methodologies. To quantify spatial patterns, fragmentation, and connectivity, the landscape metrics package was used to compute R for the landscape metrics, namely, percentage of landscape (PLAND), number of patches (NP), patch density (PD), total edges (TE), and aggregation index (AI).

The results reveal a dramatic increase in built-up areas from 73 km² (4.41%) in 1995 to 131 km² (7.92%) in 2009 and 409 km² (24.73%) in 2024, reflecting a 20.31 percentage point rise. Urban expansion into peri-urban zones has displaced agricultural land and the natural vegetation, creating hotspots of environmental vulnerability characterised by the threat of increased flooding, vegetation loss, and heat stress. Fragmentation was found to intensify, with NP rising from 5,432 to 26,368 and TE increasing by more than sixfold, whereas declining AI values indicated weakened patch connectivity.

This study shows how urban growth threatens natural ecosystems, infrastructure, mobility, and green spaces. Unlike recent socio-economic studies, it offers a spatially explicit assessment of growth, fragmentation, and directionality. The findings provide vital insights for developing sustainable land-use policies and planning to promote the resilience of Dar es Salaam, while contributing to the global sustainability goals, (SDG 11, 13, and 15).

South African Journal of Geomatics

Spatio-temporal Assessment of Soil Erosion Risk in the Tono River Basin, Upper East Ghana, using the RUSLE Model

Dynamics of Urban Sprawl in Dar es Salaam: a Three-decade Analysis using Remote Sensing and Landscape Metrics