Production of profile and three dimensional surface maps of a micro portion along the Nigerian Coast, Lagos State, Nigeria

Abstract

In this study, shoreline profile and three-dimensional surface map were created from an integrated topographic and bathymetric survey dataset obtained  using global navigation satellite system operating in real-time kinematic (GNSS RTK) mode, a cutting-edge field measurement technique that  has revolutionised and further reduced the burden of lengthy data collection times associated with traditional methods. After appropriate interpolation,  the three-dimensional map produced shows how the transition from the land-water interface blended. The topographic elevation was 1.7 m, and the  highest point measured from it was 8 m, while the bathymetric elevation was 0.5 m, and the highest sounding depth was -9 m. The computed  uncertainties were 0.5 m ±0.515, and 5 m + (-0.47) for the vertical and horizontal, respectively. The beachhead elevation ranges from +3 m to +6 m, and  the cross-section of the beach has a uniform slope from the zero mark of the site datum over a horizontal distance of 230 m to an elevation of -7 m  seaward. Subsequently, the bed topography rises slightly to describe an underwater ridge with a bump ranging between 1 m and 4 m in height. The  profile then levels off at a very gentle gradient of between -8 m and -9 m in elevation. The formation of the underwater dune feature lies just at the front  of the groyne heads. Its formation might have been influenced by the groynes. However, in the middle part of the profile map, the feature was not well  pronounced. In conclusion, the information provided in this paper can assist in safe navigation and provides data for various engineering designs aimed  at solving an environmental problem, such as the construction of shore protection for addressing coastal erosion in the study area.