Impacts of the Tropical Cyclone Idai in Mozambique: A Multi-Temporal Landsat Satellite Imagery Analysis

Alberto Bento Charrua,Salomão Bandeira,Pedro Cabral,Maria M Romeiras,Rajchandar Padmanaban

doi:10.3390/rs13020201

Alberto Bento Charrua, Salomão Bandeira + Show 3 more

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https://doi.org/10.3390/rs13020201

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Abstract

The Central Region of Mozambique (Sofala Province) bordering on the active cyclone area of the southwestern Indian Ocean has been particularly affected by climate hazards. The Cyclone Idai, which hit the region in March 2019 with strong winds causing extensive flooding and a massive loss of life, was the strongest recorded tropical cyclone in the Southern Hemisphere. The aim of this study was to use pre- and post-cyclone Idai Landsat satellite images to analyze temporal changes in Land Use and Land Cover (LULC) across the Sofala Province. Specifically, we aimed—(i) to quantify and map the changes in LULC between 2012 and 2019; (ii) to investigate the correlation between the distance to Idai’s trajectory and the degree of vegetation damage, and (iii) to determine the damage caused by Idai on different LULC. We used Landsat 7 and 8 images (with 30 m resolution) taken during the month of April for the 8-year period. The April Average Normalized Difference Vegetation Index (NDVI) over the aforementioned period (2012–2018, pre-cyclone) was compared with the values of April 2019 (post-cyclone). The results showed a decreasing trend of the productivity (NDVI 0.5 to 0.8) and an abrupt decrease after the cyclone. The most devastated land use classes were dense vegetation (decreased by 59%), followed by wetland vegetation (−57%) and shrub land (−56%). The least damaged areas were barren land (−23%), barren vegetation (−27%), and grassland and dambos (−27%). The Northeastern, Central and Southern regions of Sofala were the most devastated areas. The Pearson Correlation Coefficient between the relative vegetation change activity after Idai (NDVI%) and the distance to Idai’s trajectory was 0.95 (R-square 0.91), suggesting a strong positive linear correlation. Our study also indicated that the LULC type (vegetation physiognomy) might have influenced the degree of LULC damage. This study provides new insights for the management and conservation of natural habitats threatened by climate hazards and human factors and might accelerate ongoing recovery processes in the Sofala Province.

Highlights

Tropical cyclones are among the most devastating natural disasters owing to their great potential for loss of human life, significant economic decline and severe environmental damage [1,2,3]
The kappa coefficient (>0.80) (Table 3) shows a high accuracy level, indicating a good agreement between the Land Use and Land Cover (LULC) map for April 2019 and ground-truth based on Google Earth Engine (GEE) images [35,47]
This study focuses on an analysis of the damage caused to the LULC by Cyclone

Summary

Introduction

Tropical cyclones are among the most devastating natural disasters owing to their great potential for loss of human life, significant economic decline and severe environmental damage [1,2,3]. The Southwestern Indian Ocean is one of the main tropical cyclone areas. 2021, 13, 201 in the world [4], and the most cyclone active area in the Southern Hemisphere [5]. The Central region of Mozambique, including the Sofala Province, is the area most prone to cyclones (six cyclones in 16 years) and climate hazards. This region is characterized by a large tidal range (up to 7 m), and extensive low flatland [9,10,11]. The most severe tropical cyclones striking Sofala and affecting the lives of millions of inhabitants were—Nadia in 1994, Bonita in 1996, Lisete in 1997, Eline in

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