Coastal evolution assessment and prediction using remotely sensed front vegetation line along the Nigerian Transgressive Mahin mud coast

Abstract

Over the past decades, the Transgressive Mahin mud coastline has drastically receded due to the continuous impacts of waves and the intensifying frequency of floods. Consequently, changes in the coastline positions for the past 20 years were investigated using multispectral satellite images within the Geographic Information System environment. The study area was divided into three sectors, and the sectors were further divided into several transects at uniform intervals. Statistical Linear Regression Rate (LRR), Endpoint Rate (EPR) and Root Mean Square Error (RMSE) methods were used to assess the rates of changes in coastline positions. Also, future coastline positions for 2022 and 2029 were predicted and estimated. The study revealed that more land area was lost in the eastern sector than any other sector after about 95% of the coastline along the entire region eroded from 2015 to 2019. This confirms a shift of erosion dominance from the central sector, which has been the most vulnerable to coastal hazards over the past decades. In the same period, it was revealed from the transect rates that about 51% of the western sector’s coastline experienced accretion attributable to sand deposition from the adjacent Barrier-lagoon coast, though, approximately 65% of the coastline along the same sector had previously eroded from 1999 to 2015. Based on these findings, and without immediate response to the coastal challenges, about 3.6 km 2 and over 11.3 km 2 could be lost by 2022 and 2029, respectively. To develop a practical solution, recent changes and future projections would need to be factored in. Therefore, the relevance of this study cannot be overemphasised, as it (i) identified areas of erosion, (ii) predicted future changes of the coastline, (iii) aims to start a new trend of future projections to enhance decision making and (iv) proposed a management plan for the area.