ASSESSING FLOOD RISKS USING RADAR TECHNOLOGIES

BY STEPHEN GREENWELL

With a $675,000 grant from NASA, researchers at the University of Houston's Cullen College of Engineering and the University of California, Irvine are launching a new flood risk assessment project focusing on sandy beaches and dunes.

Pietro Milillo, Assistant Professor of Civil and Environmental Engineering, will work on the research with Brett Sanders, UCI Professor of Civil and Environmental Engineering. Together, they will develop new observational strategies and techniques to measure sandy beaches and dunes, and use technologies like interferometric synthetic aperture radar and lidar, which involves targeting an object with laser light to obtain precise size and distance measurements.

In an early phase of the project, the team will data provided by the German Aerospace Center’s TanDEM-X and NASA’s IceSAT-2 satellites with surface elevation models and lidar observations at four beach/dune sites in Southern California. The researchers will conduct measurements on a monthly and in some cases sub-monthly basis for three years.

“Our first goal is document surface elevation changes in very high resolution and to verify if our satellite-based approach can match the accuracy we can achieve with proven groundbased and aerial sensors,” said Milillo, who is a past associate project scientist in UCI’s Department of Earth System Science. “If this proves successful, we’ll be positioned to document surface elevation along all coasts every month, with better coverage and at lower costs to coastal communities than has ever been possible before.”

Sanders described some of the reasoning for why this research is so important.

“Some of the most densely populated parts of the world are adjacent to low-lying coastal terrain,” he said. “Scientists are predicting that flood risks will increase tenfold in these regions over the next 30 years based on sea level rise, but these numbers could be much higher or lower depending on how beaches respond.”

Sanders emphasized that coastal topography, including beaches and the contour of the ocean floor in shallow water near the coast, is a primary contributor to coastal flood risk. “Sea level rise presently amounts to several millimeters per year, but beach topography can change by more than a meter in a single year. We won’t have good estimates of future flood risks along wave-dominated coasts like those found in Southern California without better data characterizing changes in topography.”

This work could lead to improved understanding of sand movement, identification of hot spots of sand depletion, and early detection of beach thinning that could help to trigger early action on adaptation projects.

The NASA-funded project also will include modeling of coastal flood risks based on the observed changes in beach topography along with data characterizing coastal waves, tides and sea level changes.

“We know future flood risks are increasing, but it’s been difficult to say exactly by how and when. This work will increase our confidence in flood risk estimates for the next several decades,” Sanders said.

The team will seek answers to several key questions, including: How can large-scale geological hazards be accurately forecast in a socially relevant timeframe? How will local sea level change along coastlines around the world in the next decade to century? And what processes and interactions determine the rates of landscape change?

“Much of our work will revolve around choosing the right tools for any given type of measurement, considering their effectiveness and relative cost,” Sanders said. “The ultimate goal is to help the planning and public policy communities come up with sound strategies and infrastructure answers to deal with coastal flooding in the future.”

The ultimate goal is to help the planning and public policy communities come up with sound strategies and infrastructure answers to deal with coastal flooding in the future.