Summary:
Understanding how pollution spreads through complex estuarine environments is essential for protecting coastal communities and ecosystems. At the University of Houston, environmental engineer Hanadi Rifai has developed a new computer model that offers a more accurate way to simulate the transport of pollutants in these dynamic systems.
Her work, published in Environmental Science and Pollution Research, focuses on the Houston Ship Channel-San Jacinto River estuary within the broader Galveston Bay region — an area vulnerable to both natural hazards and industrial pollution.
Rifai’s model uses the Environmental Fluid Dynamics Code (EFDC) to examine the interplay between hydrodynamics, sediment movement, and pollutant dispersion, particularly during extreme weather events like hurricanes and heavy rainfall. By incorporating multiple sediment and water layers, as well as tracking pollutants from different sources, the model simulates how pollution moves through the system under a range of conditions.
Her findings suggest that rainfall and storms significantly alter flow speed and sediment behavior, influencing where pollutants are deposited or resuspended. This approach not only sheds light on environmental risks following extreme events but also helps inform strategies to keep estuarine systems resilient. Rifai emphasizes that long-term sampling and realistic rainfall scenarios are vital to calibrating models that can guide water quality management.
UH researcher unveils new model to evaluate impact of extreme events and natural hazards
When you’re on a sandy beach or the banks of a river, transformed by rolling waves or slightly still waters, it’s likely you’re not thinking about what happens just beneath the surface, where dirt and pollution are swirling and traveling through to new destinations.
But Hanadi Rifai does. The Moores Professor of Civil and Environmental Engineering and director of the Hurricane Resilience Research Institute, has spent two decades examining Galveston Bay – its tides, currents and how fresh and salty water mix, continually extending the knowledge of predicting water levels, pollution spread and how ecosystems stay balanced.
Now Rifai has created a sophisticated numerical computer model to help scientists and environmental experts understand how water moves in estuaries — places where fresh and saltwater mix.
“Models such as this one will be critical for evaluating climate variability and sea level fluctuation impacts on these lifeline systems for coastal communities,” reports Rifai, whose work will also guide better decisions to keep water clean, protect wildlife, and prevent flooding and pollution from spreading.
Through the years Rifai has focused on emerging pollutants and pathogenic pollution and has conducted multiple sampling campaigns including sampling associated with hurricanes Ike and Harvey. She says the importance of taking samples over time and incorporating rainfall events and stream flows into predictive estuarine models cannot be overly emphasized.
“An important lesson learned has been that the estuary while thriving and vibrant, is a complex system with many ‘moving parts’, and is sensitive to external influences that include extreme events (hurricanes, high winds, tidal fluctuations, extreme rainfall, drought, extreme heat, and industrial accidents and incidents),” said Rifai. “Historical uses have left their ‘footprint’ and continuing uses such as navigation, and recreation and municipal and industrial discharges are also associated with a ‘trace’.”
The analysis:
- Rainfall made water move faster, especially in the deep water
- Where rivers met the estuary, water flow and speed were more unpredictable
- Storms reduced salt but increased the amounts of suspended sediment in the water column (the surface to the bottom)
- Rainy days also increased sediment, which supports the idea of sediment mobilization during storms. The latter causes redistribution of pollutants within the estuary.
“The interactions between the water column and the underlying sediment and how to model those was a key focus in addition to evaluating the influence of extreme rainfall and hurricanes on identifying depositional versus erosional parts of the system,” said Rifai.
Members of the team include Adithya Govindarajan, Gradient Corp., Boston, Martin Nguyen, a graduate student in the Rifai lab.
Journal Reference:
Govindarajan, A., Rifai, H.S. & Nguyen, M., ‘Modeling water column dynamics in an urban estuary and their impacts on pollutant transport and system behavior’, Environmental Science and Pollution Research 32, 8959–8974 (2025). DOI: 10.1007/s11356-025-36258-x
Article Source:
Press Release/Material by University of Houston
Featured image credit: Thaddious Thomas | Unsplash
