Spatio-temporal Analysis of Shoreline Positional Change of Ondo State Coastline Using Remote Sensing and GIS: A Case Study of Ilaje Coastline at Ondo State in Nigeria

Shoreline changes have been a major environmental concern to coastal geomorphologists, engineers’ as well coastal ecologists as a result increased alteration in the ecological system of many coasts of the world. It is causing major coastal structure damage and requires harbour dredging. The current study aimed at integrating remote sensing, geographical information system, and statistical methods to monitor and quantify spatio-temporal shoreline dynamics along Ilaje Local Government, Ondo State, Nigeria over 31 years (1986–2017). Four multi-temporal and spectral Landsat satellite images were used to examine the shoreline changes for a long-term period (1986–2017), besides three short-term time intervals. Images were classified using supervised classification to map the land use land cover changes in the study area. Integrating the Digital Shoreline Analysis System version 4.3 tool within ArcGIS facilitated the quantification of shoreline changes via the End-Point Rate and Net Shoreline Movement statistical techniques. The study revealed a coastal length of about 80 km with both accretion and erosion processes actively shown along the coastline. About 40 km of the coastline was found to be accreting with an average of + 1.08 m/year followed by 35.4 km of coastal erosion with an average of − 1.40 m/year and 4.6 km of the coast more or less appears stable. The overall shoreline changes fall within high accretion (> + 1 to ≤ + 2) to high erosion (< − 1 to ≥ - 2) of shoreline classification. The results show significant erosion, which could impact high economic, social, and environmental costs. The study provides baseline information on shoreline dynamism in the coastline areas of Ilaje Ondo State which will serve as a veritable data for the sustainable control of coastal erosion in the study area and other shoreline with similar characteristics.