Mean Sea Level Analysis and Coastal Inundation Mapping of Lagos State, Nigeria Using Google Earth Engine
Lungfa Collins Wuyep
National Space Research and Development Agency, Centre for Geodesy and Geodynamics Toro, Bauchi State, Nigeria.
Kingsley Maraizu Ogbuagu
*
Department of Physics/Geophysics, Ignatius Ajuru University of Education, Rumuolumeni, Port Harcourt, Rivers State, Nigeria.
David Okalla
National Space Research and Development Agency, Centre for Geodesy and Geodynamics Toro, Bauchi State, Nigeria.
Valentine Okuru
Department of Physics/Geophysics, Ignatius Ajuru University of Education, Rumuolumeni, Port Harcourt, Rivers State, Nigeria.
Ramatu Aliyu Bello
National Space Research and Development Agency, Centre for Geodesy and Geodynamics Toro, Bauchi State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Lagos State is a rapidly growing coastal region where population pressure, infrastructure development and low-lying terrain increase exposure to coastal inundation. This study integrated Sentinel-1 Synthetic Aperture Radar, Shuttle Radar Topography Mission Digital Elevation Model data and Google Earth Engine processing to assess mean sea-level trend and coastal inundation vulnerability between 2010 and 2023. The analysis used simulated sea surface height data, SAR-based water detection and an elevation-based vulnerability approach to identify low-lying and high-risk zones. The sea surface height analysis indicated a relative sea-level rise rate of 3.8166 mm/year, equivalent to an estimated cumulative increase of 53.43 mm, or approximately 5.34 cm, over the study period. Terrain analysis showed that land below 5 m above mean sea level occupied approximately 1534.1 km², while the high-vulnerability zone covered approximately 1527.9 km². Seasonal water extent derived from SAR data was 667.7 km² during January–March 2023 and 653.1 km² during June–August 2023. Monthly climatology showed that sea surface height generally increased from February to August, with the highest relative flood-risk period occurring between June and October. The findings indicate that low elevation is a major control on coastal inundation vulnerability in Lagos State and highlight the need for regular monitoring, improved elevation data and integration of vulnerability mapping into coastal planning.
Keywords: Sea-level rise, coastal inundation, coastal vulnerability, sea surface height, Sentinel-1 SAR, SRTM DEM, Google Earth Engine, coastal geomorphology, low-elevation coastal zone, Lagos State