Abstract
Barrier islands (BIs) are the first line of defense against the sea/wave actions in coastal areas, and assessing their stability is crucial in the context of effective coastal planning. Therefore, this study evaluates the spatial–temporal shoreline changes of the BIs in Pakistan over the past three decades (1989–2018). Satellite data from Landsat missions are used to delineate the shorelines of 19 BIs in Pakistan. After delineating the shorelines from satellite observations, two well-known statistical methods (i.e., end point rate (EPR) and linear regression rate (LRR)) are used to capture the localized changes in the BIs. The results ascertain that nearly all of the BIs have experienced noteworthy erosion during the past three decades. While the mean erosion over all the BIs during the study period is estimated to be >6 m/y, significant spatial heterogeneities among the individual BIs exist. The interdecadal comparison indicates that the highest mean erosion of the BIs occurred during the period 1989–1999 (13.03 ± 0.62 m/y), which gradually reduced over the preceding decades (i.e., 7.76 ± 0.62 m/y during the period 1999–2009 and 3.8 ± 0.7 m/y during the period 2009–2018). Nevertheless, ~65% of the total BIs experienced high erosion (>2 m/y), ~15% experienced moderate (<2 m/y), and ~20% experienced low erosion (<1 m/y) during the period 1989-2018. This situation implies that while ~65% of these BIs need immediate interventions from the concerned authorities, the 15% BIs with moderate erosion might experience high erosion in the wake of rising sea levels and decreasing sediment influx in the near future without proper measures. This depletion of the BIs might not only affect Pakistan but also have regional consequences due to their various services.
Highlights
Due to the significance of barrier islands (BIs) as the first line of natural defense to protect coastal communities against storm surges and provisioning of multiple services, considerable interest surrounds their health/stability for a better regional environment [1,2,3].BIs provide essential economic services to coastal populations as well as serve valuable ecological functions supporting regional coastal sustainability
To check the accuracy of the results, the vector shoreline representing the boundary of each BI was examined with the corresponding false-color combination of Landsat images
This overlay analysis helped us visually verify the alignment of the BI perimeters with the seaward edge of vegetation representing BI boundaries on Landsat images and to ensure the quality/reliability of the results, as practiced by Sajjad et al [7]
Summary
Due to the significance of barrier islands (BIs) as the first line of natural defense to protect coastal communities against storm surges and provisioning of multiple services, considerable interest surrounds their health/stability for a better regional environment [1,2,3].BIs provide essential economic services to coastal populations (e.g., supporting tourism) as well as serve valuable ecological functions (e.g., providing natural habitats to several species, such as migratory birds) supporting regional coastal sustainability. In the wake of climate change-induced sea-level rise and increasing anthropogenic pressures on coastal systems, it is essential to track the changes in the geometry, area, and position of BIs, those bordering the developing and low-lying deltaic coasts. This information on coastal changes could help in taking appropriate measures for coastal resilience and sustainability [7]. In the wake of climate change, it is imperative to track the shoreline changes [5], those bordering the developing and low-lying deltaic coasts, to take appropriate measures for their stability. Previous studies conducted in different parts of the world, such as Bangladesh [14], Egypt [15], the Mediterranean sea [16], the coast of North America [17,18], Mississippi River Deltaic
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