Page 44: of Marine Technology Magazine (November 2015)

Fresh Water Monitoring (Image: NASA Landsat)

Predicting the Shape of River Deltas

Predicting the shape of river deltas around the world; new method may help engineers determine coastal impact of dams and levees.

he Mississippi River delta is a rich ecosystem of bar- “crenulated” outline, resembling a bird’s foot.

rier islands, estuaries, and wetlands that’s home to The new metric may help engineers determine how the shape a diverse mix of wildlife — as well as more than 2 of a delta, such as the Mississippi’s, may shift in response to

Tmillion people. Over the past few decades, the shape engineered structures such as dams and levees, and environ- of the delta has changed signi? cantly, as ocean waves have mental changes, such as hurricane activity and sea-level rise.

carved away at the coastline, submerging and shrinking habi- Jaap Nienhuis, a graduate student in the MIT-WHOI Joint tats. Program in Marine Geology and Geophysics, says the effects

To keep ? ooding at bay, engineers have erected dams and of climate change, and the human efforts to combat these ef- levees along the river. However, it’s unclear how such protec- fects, are already making an impact on river deltas around the tive measures will affect the shape of the river delta, and its world.

communities, over time. “Because there are so many people living on a river delta,

Now researchers from MIT and the Woods Hole Oceano- you want to know what its morphology or shape will look like graphic Institution (WHOI) have devised a way to predict a in the future,” Nienhuis says. “For the Mississippi, the river river delta’s shape, given two competing factors: its river’s supplies a lot of sediment. But because there are a lot of dams force in depositing sediment into the ocean, and ocean waves’ on the Mississippi nowadays, there is not as much sand com- strength in pushing that sediment back along the coast. De- ing down the river, so people are very worried about how this pending on the balance of the two, the coastline of a river del- delta will evolve, especially with sea-level rise, over the com- ta may take on a smooth “cuspate” shape, or a more pointed ing centuries.”

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