Spatiotemporal exposure intensification from peri-urban encroachment on oil pipelines in Ghana using a proximity-based index

Abstract

Rapid peri-urban expansion is increasingly reshaping land use around critical linear infrastructure, particularly in regions where development control and spatial monitoring capacity are limited. Proximity-based zoning frameworks are widely used to delineate infrastructure safety corridors, but are commonly applied as static regulatory thresholds ill-suited to monitoring how encroachment redistributes exposure over time. This study operationalises and applies a Proximity-Based Risk Index (PBRI) to evaluate spatiotemporal changes in built-structure exposure around an underground petroleum pipeline corridor in Savelugu Municipality, northern Ghana. Multitemporal satellite imagery (2008 to 2024), reconstructed pipeline alignment data, and digitised built structures were analysed within a reproducible geospatial workflow. Proximity was computed from densified pipeline reference geometry, and exposure was classified into graded zones derived from a Potential Impact Radius framework. The PBRI integrates proximity-weighted built-structure counts with temporal normalisation to provide a longitudinal screening metric, assessed using Mann–Kendall trend analysis and Sen’s slope estimation. Results indicate a gradual redistribution of built structures toward higher-exposure bands despite substantial overall urban growth. The PBRI rose from 1.035 in 2008 to a peak of 1.074 in 2021 (1.072 by 2024), a statistically significant monotonic trend (τ = 0.889, p = 0.0012); over the same period, structures within the highest-exposure zone increased nearly fivefold (from 33 to 159). Kernel density patterns corroborate progressive clustering along the corridor. By treating proximity as a dynamic exposure gradient, the PBRI offers an exposure-monitoring and screening tool for data-scarce peri-urban environments rather than a predictive risk model, supporting corridor-sensitive infrastructure governance across rapidly urbanising Global South contexts.