An increased number of floods, due to reduced river gradients, higher rainfall in the Ganges-Meghna-Brahmaputra river basins, and the melting of glaciers in the Himalayas, is considered the major reason for migration in the context of climate change in Bangladesh over all. Bangladesh sits at the head of the Bay of Bengal, astride the largest river delta on Earth, formed by the junction of the Brahmaputra, Ganges, and Meghna rivers. Nearly one-quarter of Bangladesh is less than seven feet about sea level; two-thirds of the country is less than 15 feet above sea level. Most Bangladeshis live along coastal areas where alluvial delta soils provide some of the best farmland in the country.