River avulsions, the sudden and dramatic changing of a river’s course, have been a dangerous phenomenon throughout history, causing devastating floods and threatening millions of people worldwide. Indiana University researchers, led by James “Jake” Gearon, have made a breakthrough in understanding river avulsions, outlining the conditions that create them for the first time. Using advanced satellite technology known as lidar, the team mapped landscape features that make avulsions more likely, providing a new framework for predicting when and where they may occur.
Avulsions occur when a river’s water rises above the surrounding landscape, often due to sediment buildup in the riverbed, causing the river to carve a new path across the floodplain. This can lead to severe flooding and has historically caused major disasters, such as the 2008 avulsion of the Kosi River in Northern India that directly affected over 30 million residents. The study challenges traditional beliefs about the causes of avulsions, finding that both the elevation of the riverbed and the slope of the surrounding land play a role in determining where a river may change course.
Analyzing data from 174 river avulsions worldwide, researchers found that avulsions are more common near mountain ranges and coastal areas, where sediment buildup is more likely. They developed a new model to map “avulsion corridors” that predict where rivers might change course, helping governments and planners identify areas at high risk for sudden flooding. This new tool could be especially valuable in the Global South, where avulsions are more frequent and deadly, due to a combination of geological factors and infrastructure challenges.
Traditionally, flood hazard assessments have not taken avulsions into account, focusing instead on rising water levels from heavy rains. However, avulsions can occur without warning and in areas where rainfall isn’t a major concern, making them particularly dangerous and difficult to predict. The study emphasizes the importance of considering avulsions in flood hazard assessments and offers a new way to plan for and mitigate the risks posed by river avulsions, providing essential tools for understanding and addressing this dangerous phenomenon.
As climate change alters global water cycles and increases flood hazards worldwide, understanding and predicting river avulsions has never been more critical. By offering a new model for mapping flood risks and predicting avulsions, the research conducted by the Indiana University team provides valuable insights for scientists, policy makers, and practitioners. This research has the potential to save lives and reduce economic damage in regions vulnerable to sudden river changes, offering a way to plan for and respond to the dangers posed by river avulsions in an increasingly volatile natural environment.