Why Did Nepal’s Great Floods Happen? ― How Himalayan Debris Flows Shaped the Ganges Plain and the Geography of the Indus Civilization
The Himalayas are one of the most dynamic natural environments in the world. Formed by the collision of the Indian and Eurasian tectonic plates, this vast mountain range continues to rise even today. At the same time, monsoon rains, snow, glaciers, and rivers are constantly eroding its towering mountains. As a result, the Himalayas are a place where mountains are being built and broken down at the same time. Disaster and Prosperity Born in the Himalayas The recent large-scale flash flood in the Rasuwa region of north-central Nepal, near the border with Tibet, China, is another event that illustrates the dynamic nature of the Himalayas. The Himalayas and the Rasuwa Flood Area in Nepal However, it is difficult to explain this event simply as “a flood caused by heavy rainfall.” In high mountain regions, large-scale movements of water, rock, and sediment can travel down valleys and river channels, triggering debris flows, blocking rivers, forming natural dams, and eventually producing sudd...