DefinePK

Research Objective

To calculate and analyze shoreline changes and morphological changes along the Karachi coast over the last two decades using the Digital Shoreline Analysis System (DSAS).

Methodology

The study utilized Landsat satellite imagery (Landsat 7 ETM+ and Landsat 8 OLI/TIRS) from 2000 to 2022, with data obtained at 5-year intervals. Shorelines and a baseline were digitized using Google Earth Pro. The Digital Shoreline Analysis System (DSAS) was employed within ArcMap to calculate shoreline change statistics, including Shoreline Change Envelope (SCE), Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR).

Methodology Flowchart

                        graph TD;
    A[Acquire Landsat Satellite Imagery 2000-2022] --> B[Organize Imagery in ArcMap/QGIS];
    B --> C[Digitize Shorelines and BaselineGoogle Earth Pro];
    C --> D[Apply Digital Shoreline Analysis System DSAS];
    D --> E[Calculate Shoreline Change StatisticsSCE, NSM, EPR, LRR];
    E --> F[Analyze Erosion and Accretion Patterns];
    F --> G[Predict Future Shoreline Changes];
    G --> H[Draw Conclusions and Implications];                    

Discussion

Morphological changes along the Sindh coastline, including Karachi, are influenced by a combination of natural factors (waves, currents, sea level rise) and anthropogenic activities (construction, urbanization, industrial development, removal of mangroves). The study highlights that sea level rise, exacerbated by human activities, is a significant concern for the Karachi coast. The findings align with previous studies indicating erosion in the eastern parts of Karachi and accretion in the southern regions.

Key Findings

Over the last two decades, the Karachi coast has experienced both erosion and accretion. Erosion dominated the entire coastline, particularly in the Bin Qasim town area, while accretion was observed in Korangi town. The calculated statistics for the last two decades are: SCE of 427.76 m, NSM of -46.02 m, EPR of -3.22 m/yr, and LRR of -2.16 m/yr. Erosion accounted for 49.29% of the observed changes, while accretion accounted for 25.59%. The year 2015 showed the most significant shoreline changes.

Conclusion

The DSAS model effectively identified and quantified shoreline changes along the Karachi coast over the past two decades and provided future predictions. Erosion is predominantly observed in Bin Qasim town, while accretion is noted in the southern parts. The study emphasizes the critical role of remote sensing and GIS in coastal risk assessment and prediction, underscoring that rapid coastal development significantly alters coastal morphology. Sea level rise due to anthropogenic activities poses a major threat to the Karachi coast.

Fact Check

* Shoreline changes were calculated for the last two decades (2000-2020).
* Net Shoreline Movement (NSM) was -46.02 m.
* End Point Rate (EPR) was -3.22 m/yr.

Mind Map