Assessment of Bathymetry and Seafloor Features in Apapa Harbour, Lagos

Accurate bathymetric knowledge is foundational to safe maritime navigation, dredging planning, and port management, particularly in dynamically evolving harbour environments subjected to intensive shipping traffic. This study conducts a bathymetric survey of Apapa Harbour, Lagos State, South West Nigeria, Nigeria's most active deep water commercial port, to characterise current water depths, identify hazardous shoal areas, and detect changes since the last authorised hydrographic survey. Single-beam echo sounding surveys are conducted along closely spaced parallel transects at 25-metre line spacing using a calibrated Odom Hydrotrac II sounder, with positioning provided by a dual-frequency GNSS receiver operating in real-time kinematic mode. Tidal corrections are applied using water level data from the National Port Authority tide gauge at Apapa, and data are reduced to Chart Datum. Sediment sampling at 30 stations characterises seafloor substrate and assesses the risk of dredged material dispersal. Acoustic sub-bottom profiling delineates sediment layer thickness and identifies buried infrastructure hazards. The resulting bathymetric chart is compared with NGA chart 54251 (2019 edition) to quantify depth changes and net sedimentation volumes. Results are expected to reveal shoaling of up to 1.5 metres in the main channel fairway and at berth approaches. The study delivers updated bathymetric data and dredging volume estimates to the Nigerian Ports Authority and provides the basis for revised port nautical charts. Keywords: bathymetry, Apapa Harbour, echo sounding, port hydrography, Lagos maritime