Three Decades of Coastal Changes in Sindh, Pakistan (1989–2018): A Geospatial Assessment

Shamsa Kanwal,Xiaoli Ding,Sawaid Abbas,Muhammad Sajjad

doi:10.3390/rs12010008

Abstract

Coastal erosion endangers millions living near-shore and puts coastal infrastructure at risk, particularly in low-lying deltaic coasts of developing nations. This study focuses on morphological changes along the ~320-km-long Sindh coastline of Pakistan over past three decades. In this study, the Landsat images from 1989 to 2018 at an interval of 10 years are used to analyze the state of coastline erosion. For this purpose, well-known statistical approaches such as end point rate (EPR), least median of squares (LMS), and linear regression rate (LRR) are used to calculate the rates of coastline change. We analyze the erosion trend along with the underlying controlling variables of coastal change. Results show that most areas along the coastline have experienced noteworthy erosion during the study period. It is found that Karachi coastline experienced 2.43 ± 0.45 m/yr of erosion and 8.34 ± 0.45 m/yr of accretion, while erosion on the western and eastern sides of Indus River reached 12.5 ± 0.55 and 19.96 ± 0.65 m/yr on average, respectively. Coastal erosion is widespread along the entire coastline. However, the rate of erosion varies across the study area with a general trend of erosion increasing from west to east in the Indus Delta region (IDR), and the highest average erosion rate is 27.46 m/yr. The interdecadal change during 1989–1999, 1999–2009 and 2009–2018 periods depicted an increasing linear trend (R2 = 0.78) from Karachi to Indus River (IR) East zone. The spatial trend from west to east is positively correlated with mean sea level rise, which has increased from 1.1 to 1.9 mm/year, and negatively correlated with topographic slope, which is found to be decreasing eastward along the coastline. The findings necessitate appropriate actions and have important implications to better manage coastal areas in Pakistan in the wake of global climate change.

Highlights

Coastal degradation endangers millions living near-shore and puts coastal infrastructure at risk.Impacts of coastal erosion are often sudden, making it a major coastal hazard [1,2]
In order to evaluate the coastline accuracy, initially we searched for high-resolution data such as aerial orthophotos or freely available high-resolution satellite images such as Sentinel-2 that coincide with dates of Landsat images used
This study evaluates the spatial heterogeneities in the large-scale morphological changes along the Pakistan coastline on zonal and subzonal scales during the past three decades (1989–2018)

Summary

Introduction

Coastal degradation endangers millions living near-shore and puts coastal infrastructure at risk. Impacts of coastal erosion are often sudden, making it a major coastal hazard [1,2]. The situation is more appalling in low-lying deltaic regions in developing nations (such as Pakistan, Philippines, and Bangladesh), which are less prepared to cope with the risks. The trends and rates of morphological change of the highly dynamic land–water transition interface, known as coastline, represent the summaries of various coast-influencing processes such as SLR and storm surges [6]. Anthropogenic activities are another major factor accelerating coastal

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Results

Conclusion