72 Journal of Geomatics Vol. 14, No. 1, April 2020 Long-term determination of shoreline changes along the coast of Lagos Peter C. Nwilo1*, A. Chidi Ibe2, Jimmy O. Adegoke3, Jerry N. Obiefuna4, Alfred S. Alademomi1, Chukwuma J. Okolie1, Olayemi O. Owoeye1, Joel N. Nwokocha1, Michael J. Orji1, Abdulkareem A. Umar1 and Olagoke E. Daramola1 1Department of Surveying & Geoinformatics, Faculty of Engineering, University of Lagos, Akoka, Lagos State, Nigeria 2Institute for Natural Resources, Environment and Sustainable Development, University of Port-Harcourt, Rivers State, Nigeria 3Department of Geoscience, Centre for Applied Environmental Research (CAER), University of Missouri, Kansas City, USA 4Department of Architecture, Enugu State University of Science & Technology, Enugu, Enugu State, Nigeria *Email:
[email protected] (Received: Feb. 08, 2020; in final form: June 24, 2020) Abstract: Analysis of shoreline changes is an important indicator in the study of coastal erosion and/or accretion. It aids in understanding the spatio-temporal trends in the changes triggered by natural processes and human impacts. The construction of two breakwaters (East and West moles) between 1908 and 1912 at the entrance to Lagos harbor inhibited the natural flow of the longshore drift, hence it accelerated erosion rate especially in the Victoria Island area while areas on the west of the breakwaters were accreting. This study relied on archival maps of 1900 – 1964 and satellite imageries of 2001–2016 to determine and visualize the magnitude of erosion and accretion along the coast of Lagos State. The shoreline positions at various epochs were extracted from the maps and satellite imagery by vectorization. The magnitude of change was determined by calculating the differences in the shoreline positions measured along vertical line segments spaced at 200-meter intervals.