Investigating and modelling ground settlement response to groundwater dynamic variation in parts of Lagos using space-based retrievals

Abstract

Ground settlement has impacted many infrastructures in Lagos. Rapid urbanisation has further compounded this problem. Monitoring and modelling of ground settlement will provide actionable information that can help to mitigate this problem. In this study, space-based retrievals were used to investigate the magnitude and spatial distribution of ground settlement and the role of groundwater depletion in Lagos. Using the SBAS technique, the ground settlement rates were computed based on the Sentinel-1 data acquired between 2015–2019. The GRACE-derived groundwater head changes between 2002–2017 was quantified, and the ground settlement response to groundwater depletion was modelled. The highest recorded groundwater depletion rate was −11 mm/year, while the highest observed ground settlement rate was −94 mm/year, indicating an intense rate of ground settlement up to the end of 2019. The statistical correlation between ground settlement and groundwater head changes is in the order of 0.4, which is a moderate positive correlation indicating a partial correlation between ground settlement and groundwater depletion. To model settlement, a one-dimensional approach was used to simulate the response of ground settlement to changes in groundwater level. The simulated results fairly correspond to the magnitude of observed settlement, confirming that factors other than groundwater depletion partly control ground settlement in Lagos.