Nearly five decades of changing shoreline mobility along the densely developed Lagos barrier-lagoon coast of Nigeria: A remote sensing approach

Abstract

Lagos is the old capital and largest port city in Nigeria. There are increased ecological and environmental problems around this coastal area with fast-growing industrialization and a population of 14 million in 2020. In this study, we utilized satellite images to study the shoreline evolution of Lagos Lagoon Barrier coast, Nigeria from 1973 to 2019. The Lagos Lagoon Barrier coast is divided into three sections: Section I (Marginal Lagos), section II (Eko Atlantic City), and section III (Lekki peninsula). Section I coast was stable compared to other sections with around 77% of the section experiencing erosion with the averaging rate of −1.73 m/yr, and the remaining 23% accreting at the rate of +0.57 m/yr throughout the study period. Around 92% of Section II was eroded at the rate of −3.59 m/yr, and 8% of this section accreting at the rate of +4.46 m/yr from 1973 to 2008, with a serious erosion rate of −11.79 m/yr from 1986 to 1999. After the Eko Atlantic City project from 2008 to 2019, Section II experienced advancement up to +92.16 m/yr (53%) and a retreat of up to −6.50 m/yr (47%). Along section III, erosion dominates with around 90% of this section being eroded at the averaging rate of −3.55 m/yr with only 10% accreting at the averaging rate of +1.10 m/yr for the study period. Along the westernmost edge of section III, intense erosion up to +7.10 m/yr dominates and continues eastward of Victoria Island from 2012 to 2019. Furthermore, we recorded shoreline erosion up to −11 m/yr along the Ibeju-Lekki axis and Lagos Free Trade Zone (eastern fringe of section III) from 1999 to 2012.Extrapolating the responsible factors for the shoreline fluctuations along the Lagos Lagoon Barrier coast, this study has identified a combined impact of sea-level rise, limited sediment supplied by longshore current from adjacent rivers due to construction of dams along the several tributaries in the Bight of Benin, hard coastal engineering procedure such as the Eko Atlantic City (section II) and Lekki deep seaport projects, and intensified population along the coastline to have contributed to the erosion feature observed along the study area. Moreover, this study has revealed that Eko Atlantic City may have contributed to the eroding coast along section III. Our final deduction shows that section I is dominated by natural shoreline change patterns and therefore primarily responded to the effect of sea-level rise. Section III is influenced by both natural and human forces while section II is influenced by human intervention through coastal protection as a result of reverse-engineering the effect of climate change and sea-level rise. Conclusively, this study has recommended that current coastal management policies and plans in Lagos State need to be reconsidered and revised to ensure the sustainable use of the coastal zone.