Scientists studying China's Yellow River have created a tool that could help officials better predict and prevent its all-too-frequent floods, which threaten as many as 80 million people.

The tool -- a formula to calculate sediment transport -- may also be applied to studying the sustainability of eroding coastlines worldwide.

"Understanding the flow of sediment in rivers is important to the large number of people around the world who live near these waterways," said Judy Skog, a program director for the National Science Foundation's (NSF) Coastal SEES (Science, Engineering and Education for Sustainability) program, which funded the research.

A Yellow River fishing boat.A Yellow River fishing boat."This study will lead to better predictions of when and where rivers transport sediment, and to an understanding of how that sediment flow is affected by conservation and management efforts, such as the removal of dams," Skog said.

Known in Chinese as the Huanghe, the Yellow River is considered the cradle of Chinese civilization, and is often called the "mother of China" for its nutrient-rich sediment. Some 1 billion tons of sediment washes down each year from the Loess Plateau to the Bohai Sea, a sediment load that can clog the river. When this happens, it can flood and also change course.

The typical formulas and relationships that are used to describe sediment flux in most other rivers don't work for the Huanghe. They consistently underpredict the sediment load of the river by a factor of 20.

In terms of sediment transport, the Huanghe is almost the perfect river, researchers say. That's because its bottom is nearly flat and featureless, which means it can use almost all of its energy for moving sediment.

In lowland, sand-bed rivers like the Amazon or the Mississippi only about 40-60% of the energy is used to transport sediment downstream. In the Yellow River, well over 95% of the energy is available to move sediment.

This means the Yellow River generates new land extremely efficiently each year, making it the best place to learn how to use sediment from rivers to enhance delta sustainability. Those lessons have applications for river systems worldwide.

Chinese engineers have long tried to reduce the risk of Yellow River floods by periodically releasing massive amounts of lake water to scour the river's bottom and keep its sediment moving. Such scouring, however, may inadvertently increase the risk of flooding in certain parts of the river, according to the new model.

Although the scouring process clears silt, it also creates a rough-textured riverbed that reduces the amount of energy the river can use to move sediment.

In previous studies, researchers found that river bottoms had features similar to desert sand dunes. When the bottom of the Mississippi was imaged, for example, researchers saw formations up to 10 meters (33 feet) tall and spaced about 200 to 300 meters (656 to 984 feet) apart. In contrast, the data from the Yellow River showed 1 meter (3.3 feet) tall dunes every 500 to 2,000 meters (1,640 to 6,562 feet).

Using measurements from the lower Yellow River and its sprawling delta, researchers created a physics-based formula capable of accurately predicting the flux -- the volume of sediment transported for a given time period -- in the Yellow River.