Multi-decadal shoreline evolution and near-future projection along the barrier-lagoon coast of Nigeria
摘要
Nigeria Barrier-Lagoon Coast (NBLC) borders Lagos, the most commercially viable state. Major economic activities occur near the coast and the migrating shoreline poses a great threat. Dredging, urbanization, and low-lying beaches have enhanced the effect of landward shoreline migration. This study assessed the rate and extent of coastal migration in the NBLC from 1987 to 2018 and predicted the shoreline position by 2038. Digital Shoreline Analysis System (DSAS) was utilised to calculate the (Linear Regression and End Point Rate of change), the extent of migration (Shoreline Change Envelope and Net Shoreline Movement). Five zones (E1—E5) were demarcated from the results. E5 showed the highest adverse net migration (-1267 to -94 m) and erosion rate (EPR: 4 to 26 m/year and LRR: 2 to 21 m/year). Other zones of concern are E3 and E1 with net migrations of -490 to -300 m and -329 to -124 m respectively. Erosion rates in these active economic hubs, E3 (9 to 16 m/year) and E1 (4 to 10 m/year), are threatening. The shoreline position by 2038 reveals a 26.1 km2 beach area loss from Seme Border to Orimedu beach, adding to the 36.1 km2 loss already recorded between 1987 and 2018. Only 11% (25.3 km) of the coastline shows accretion (8.3 km from reclamation; 17 km from natural processes). It is recommended that monitoring programme combining periodic remote-sensing surveys with in-situ measurements is implemented to regulate sand mining, guide sustainable infrastructural development, and design nature based and engineered protections to stabilize the NBLC.