Influence of Tidal Dynamics on Sediment Transport in the Lagos Harbour

Understanding the relationship between tidal dynamics and sediment transport is essential for managing navigational channels, coastal infrastructure, and the ecological integrity of estuarine habitats. This study examined the influence of tidal cycles on suspended sediment transport in Lagos Harbour, Lagos State, South West Nigeria. Tidal current velocity, direction, and water level data were collected using a current meter over thirty consecutive tidal cycles at three stations within the harbour. Suspended sediment concentration was measured in surface and mid-water samples collected at one-hour intervals during flood and ebb phases. Grain size analysis of bedload sediments was conducted using standard sieve procedures. Salinity and turbidity were also recorded concurrently. Results showed strong correlation between tidal current velocity and suspended sediment concentration at all stations, confirming tidal advection as the dominant transport mechanism. Flood tide promoted landward sediment transport, while ebb tide drove seaward movement. Net sediment flux calculations indicated a slight landward transport bias, consistent with estuarine infilling dynamics. Grain size analysis revealed fine to medium sand in the central channel, shifting to silty sediments in the peripheral areas. Turbidity maximum zones were identified at the halocline boundary during neap tides. The study provides data essential for dredging frequency estimation, port maintenance planning, and assessment of sedimentation rates in the Lagos Harbour shipping channel. Keywords: tidal dynamics, sediment transport, Lagos Harbour, suspended sediment, tidal current.