File:Flooding along the Mangoky River (MODIS 2024-01-05).jpg

English: January 4, 2024 December 25, 2023

The Mangoky River is Madagascar’s longest river as well as the major river that courses through the dry, hot western lowlands. The Mangoky begins in the country’s Central Highland region, then flows generally westerly before turning toward the northwest to spill into the Mozambique Channel just north of the city of Morombe. A wide delta, with braided channels surrounds the mouth of the Mangoky at the Mozambique Channel, but those channels remain empty almost all year, especially during the dry season (April through October). In early January 2024, torrential rain from Tropical Cyclone Alvaro brought flooding along the Mangoky River and filled the channels of the Mangoky Delta to overflowing.

Topical Cyclone Alvaro formed in the Mozambique Channel from a depression between December 30-31, 2023. It charged eastward, making landfall over southwestern Madagascar near Morombe on January 1, 2024, bringing near-hurricane force winds and severe rain. Once over land, Alvaro weakened as it crossed Madagascar. As it moved over the Indian Ocean on January 3, it once again strengthened before becoming extratropical on January 4.

The storm triggered flooding in several low-lying areas as well as along the Mangoky River. According to a report published by ReliefWeb, more than 400 people have been displaced and relocated to six evacuation sites, with at least 4,543 people affected. In addition, eight houses have been damaged, six schools completely destroyed, and four others damaged.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired a pair of false-color images that demonstrate flooding along the Mangoky triggered by Tropical Cyclone Alvero. The first, acquired on January 4, 2024, shows that the river has widened along its entire visible length, especially at the Delta, compared to the pre-storm image acquired on December 25, 2023.

In this type of false color image, water appears blue with deeper water looking darker and shallow water or sediment-laden water appearing brighter and lighter blue. Vegetation is green and open land looks tan. Clouds may appear white or may be tinted electric blue. Simply clicking on the dates below the images allows an easy comparison of the widespread flooding brought by Tropical Cyclone Alvaro.