Providing Better Flood Estimates for Roadways and Bridges in New Jersey

Challenge

During times of high water, like coastal storm events or strong tides, flooding can make travel dangerous. Flooded roadways impede travel to work, the distribution of goods, and emergency response operations—putting coastal economies and communities in harm’s way. In New Jersey, 17 of the state’s 21 counties touch a portion of its coastline, which places millions of residents at risk for flooding impacts that will only increase as sea levels rise.

Currently, estimates for when roads and bridges might flood are based on measurements at the ground level, making them less reliable for elevated roads and bridges. Researchers at Rutgers University’s Center for Urban Policy Research and New Jersey Climate Change Resource Center wanted to update this process and create more accurate assessments of roadway flooding.

Solution

To get a better picture of which roadways may flood at different high water levels, the team used lidar elevation data from NOAA’s Data Access Viewer, VDatum, and the Detailed Methodology for Mapping Sea Level Rise Inundation to create an updated digital surface model for the entire state. This model shows the height of objects like trees, buildings, and bridges with higher accuracy compared to the state’s previous models. By subtracting the height of roads and bridges from different water level increments, the team now had estimates for the roadways that could flood at each flood severity.

The improved flooding estimates will inform emergency planning, projects to elevate existing roads and bridges, and future roadway construction. (2025)

A visualization using NOAA’s 10ft sea level rise layer (blue) inaccurately shows flooding over the Mullica River Bridge, a Garden State Parkway bridge from Atlantic County into Ocean County. The red lines show where the roadway is actually flooded at 10ft inundation according to the updated analysis using lidar elevation data from NOAA’s Data Access Viewer, VDatum, and the Detailed Methodology for Mapping Sea Level Rise Inundation.

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