Predicting the shape of river deltas
The Mississippi River delta is a rich ecosystem of barrier islands, estuaries, and wetlands that’s home to a diverse mix of wildlife — as well as more than 2 million people. Over the past few decades, the shape of the delta has changed significantly, as ocean waves have carved away at the coastline, and marshes lacking new river sediment have submerged habitats. To keep flooding at bay, engineers have erected dams and levees along the river. However, it’s unclear how such protective measures will affect the shape of the delta, and affect its communities, over time. Now researchers from MIT and the Woods Hole Oceanographic Institution (WHOI) have devised a simple way to predict a river delta’s shape, given two competing factors: how fast a river forces sediment into the ocean, and ocean waves’ strength in pushing that sediment back along the coast. Depending on the balance of the two, the coastline...