Ma receives NSF CAREER Award

CEE Assistant Professor Hongbo Ma has won a CAREER Award from the National Science Foundation (NSF) for his project on the Morphodynamics of Delta Channel Networks at the Decadal Scales.

Ma's recent research, revealing a pattern on how river deltas build land and protect coastal regions from encroaching oceans, was published in the journal Science. The new study, inspired by a 1950s-era finding called Hack’s law — which states that the length of the longest tributary near the start of a river system is proportional to the size of its drainage basin — finds that coastal river deltas appear to follow a similar predictable pattern when it comes to sediment deposition.

“Hack’s law is a simple way of describing how the leading ends of rivers and their tributaries spread out across the landscape,” said Ma. “For a long time, researchers have observed similar patterns at the other end of rivers, known as deltas, but efforts to define these observations into distinct models for practical use have lagged.”

“Our study found that some deltas show uniform growth where their networks follow Hack’s law consistently,” Ma said. “Others show composite growth, meaning they spread quickly at first, filling space like ink in water, then slow down and grow mainly along a few main channels.”

The findings are significant for engineering and restoration projects and could provide a rule of thumb for estimating land build-up based on channel length, he added.

Ma plans to continue building on this research with his new project, supported by his NSF award, to develop predictive models for delta landing building in decadal scales.

CAREER Awards, administered under the Faculty Early Career Development Program, are the NSF’s most prestigious form of support and recognition for junior faculty who “exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organizations.”

Ma joined the CEE department in June 2025. His research focuses on environmental fluid mechanics, sediment-laden flows and their geomorphic expressions across diverse environments, including both mountain streams and fine-grained depositional systems. He has extensive experience in engineering projects involving flash/dambreak flood prediction, sediment yield evaluation, river management, river delta restoration, and reservoir sedimentation mitigation. In addition to his publication in Science, his project documenting the first in-field evidence of underwater sediment transport mechanisms was recently published in PNAS.