Coasts · MSc thesis & journal article

Shoreline change after four cyclones

Using Landsat 8 imagery from before and after each storm, I mapped how the coastline of Bangladesh moved after cyclones Sitrang, Bulbul, Amphan and Mocha. Stronger storms caused more erosion. Satkhira and Khulna lost the most shoreline, Bhola and Noakhali gained land through accretion, and Cox's Bazar held up comparatively well.

Coasts
Map of the coastal region of Bangladesh used as the study area
Study area: the coastal districts of Bangladesh.

Shorelines were extracted with the MNDWI water index and compared with the Digital Shoreline Analysis System (DSAS), which measures net shoreline movement along transects in metres.

Choose a cyclone below to see its shoreline change map.

Shoreline change map before and after Cyclone Amphan
Net shoreline movement (m), before and after Cyclone Amphan.
77.67%
of the measured shoreline eroded

The strongest storm in the study, with winds of about 150 mph, caused the most severe erosion.

  • Sitrang52.72%
  • Bulbul57.39%
  • Amphan77.67%
  • Mocha77.36%
How shoreline change is measured
baseline land Bay of Bengal
shoreline beforeshoreline after, shaded where land was lostDSAS transects
  1. Landsat 8 scenes before and after each landfall
  2. MNDWI separates water from land
  3. Shoreline extracted for each date
  4. DSAS transects measure erosion and accretion
  5. Coastal districts zoned by impact

Schematic illustration of the method, not measured data.

Maps from Pobon, Akter & Mahmud, preprint on Research Square, CC BY 4.0.

From the MSc thesis

What the cyclones did to vegetation

The thesis also measured vegetation health before and after each storm with the Enhanced Vegetation Index (EVI) from MODIS. The weaker storms barely changed it. Amphan stripped healthy vegetation from a quarter of the coastal region.

Enhanced Vegetation Index maps of coastal Bangladesh before and after Cyclone Amphan
EVI before and after Cyclone Amphan. Red and orange show sparse or stressed vegetation, green shows healthy cover.
−26.1
percentage points of healthy vegetation lost

Healthy cover fell from 84.1% to 58.0% of the region, while moderate vegetation rose by 24 points.

  • Sitrang−2.89
  • Bulbul−2.16
  • Amphan−26.1
  • Mocha−2.68
Map of the change in vegetation cover by coastal district after Cyclone Amphan
Change in vegetation cover by district after Cyclone Amphan.
Healthy vegetation lost after Amphan
  • Patuakhali−50.9
  • Barguna−37.8
  • Pirojpur−34.1
  • Khulna−29.1
  • Jashore−27.9

Percentage points of each district's vegetated area that dropped out of the healthy class.

Maps from my MSc thesis, Jahangirnagar University, 2024.

Publications from this project

Journal article · Main author Submitted Sep 2026

Geospatial Technology for Rapid Shoreline Change Analysis of Tropical Cyclones in Coastal Bangladesh

Pobon, M. T. A. N., Akter, R., and Mahmud, K. H. Submitted to The Jahangirnagar Review. Preprint on Research Square, November 2025 · doi:10.21203/rs.3.rs-7954742/v1

MSc thesis

Geo-spatial Technology for Rapid Eco-Physical Impact Assessment of Tropical Cyclones of the Bay of Bengal

  • Measured the physical impact of multiple cyclones with multi-temporal GIS and remote sensing, using shoreline erosion and deposition as the main indicator alongside vegetation change.
  • Quantified shoreline change for four cyclones (Sitrang, Bulbul, Amphan and Mocha) using Landsat 8 imagery, MNDWI and the Digital Shoreline Analysis System (DSAS).
  • Compared impacts across cyclone categories to gauge relative severity.
  • Zoned coastal districts by impact, giving a spatial framework for risk management.
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