Monitoring of bathymetric changes in the Commodore Channel, Lagos State Nigeria

Abstract

The Commodore Channel in Lagos State is located at the seaside entrance into the Lagos Harbour thus exposing it to the action of dynamic coastal forces such as high waves, tidal currents, and storm surges. The combined effects of these forces affect the stability of the sediments on the channel’s seabed. This study assessed changes in the channel’s bathymetry using data on water depth from a time series of bathymetric charts covering the channel at the following periods: 2008, 2010, 2012, 2014, 2016 and 2018. The charts were acquired from the Nigerian Navy Hydrographic Office (NNHO), scanned and georeferenced. The depths were digitized within the ArcGIS 10.4.1 software environment. Using Kriging interpolation, bathymetric surfaces were produced, and coincident points for depth comparison were extracted. There was an average decrease of 0.02m in depth values from 2008 to 2010 and an average decrease of 0.03m between 2010 to 2012. From 2012 to 2018, the average depth increased consistently. There was also a rapid increase in surface volume from 2008 – 2014, and a slight decrease in volume in 2016. Continuous monitoring of channel bathymetry is essential for safe navigation.