By Jugal Patel, Student Correspondent
This is Part 4 in the “Adapting to Rising Seas” series.
Below the streets of the century-old Norfolk neighborhood of Chesterfield Heights, an aging network of clay, concrete, and cast iron drainage pipes are all that protect the seaside community from a deluge of floodwater.
“Instead of installing pumps or a lot of big berms and hard engineering, we wanted to figure out how we could make the landscape absorb more water,” said Alex Carlson, a 2015 Old Dominion University (ODU) graduate in civil and environmental engineering.
In a first-of-its-kind project funded by Virginia Sea Grant (VASG) and coordinated by Wetlands Watch, Carlson and other ODU engineering students partnered with Hampton University (HU) architecture students to help Chesterfield Heights deal with its current flooding and prepare for future rises in sea level.
Working in teams focusing on the storm water system, the eroding shoreline, and frequent road flooding, ODU students tested cistern designs developed by HU architecture students and developed plans for the neighborhood to address an anticipated foot and a half of sea level rise. That increase in sea level is what state and federal agencies in Virginia expect by mid-century, according to Wetlands Watch.
Chesterfield Heights’ existing drainage system divides the neighborhood into a grid dotted with curb gutters and drop inlets, each of which allows water to flow down from street level into an underground network of pipes. Flood water is meant to move through the pipes to outfalls that drain into the Elizabeth River.
Over time, however, this storm water system has lost its ability to deal with rain events, making storm water management a challenge. The problem is partly due to the retreating coastline.
“When you add in sea level rise, you’re talking about pipes that are already submerged before the rainfall even happens,” Carlson explains. “So you’re pushing against the river that’s coming into the neighborhood.”
Solutions are made even more difficult by low-lying terrain. Raising pipes is not an option because the pipes must be placed below street level, so the water will flow from the street to the pipes. The streets, however, are at low elevations to begin with.
To account for the problem of low elevation, one ODU student engineer team proposed raising the neighborhood’s main street, Kimball Terrace Road, or converting it to a bridge structure.
“We tried to focus more on doing things on top of the ground,” explained Carlson.
Their decision to take this above-ground route came after discovering that the neighborhood’s soils are successful at soaking up water.
Based on this fact, they considered solutions that would provide more space to hold water, such as bioretention gardens along the streets. Their designs also propose adding permeable pavement to line the edges of the roads, allowing for water storage beneath.
The pavement would blend seamlessly into the existing red brick road that currently stretches down Marlboro Avenue, in the heart of the neighborhood.
The group also identified a variety of needed repairs to the stressed, undersized drainage system.
When the ODU engineers calculated how much water could be retained by these improvements, combined with the innovative new cistern designs from HU architects, they found that flooding would be significantly reduced at the street level.
Ideas to protect the waterfront itself include setting up a barrier of rocks just off the coast to buffer against waves. A group of ODU engineers also explored an idea proposed by HU architects to design an extended, living shoreline to protect against erosion.
“Over time, you’re going to get erosion and different localities need to look into creating wetlands so they can keep their shoreline looking good,” said Shanice Proctor, an ODU student who led the living shoreline design.
Living shorelines use natural materials to absorb wave energy that hits the coast. By lining a shore with wetland plants, submerged aquatic vegetation, or oyster reefs, for example, the shoreline gets the benefit of erosion control, while promoting a healthy ecosystem.
According to Proctor, living shorelines have another benefit: unobstructed views of the water. This is because living shorelines can use small marsh plants instead of trees. After consulting with residents of the neighborhood, preserving the view was a priority for the adaptation team.
“They feel that trees might disrupt the view, but the [plants] are what need to be there so that the water doesn’t spill out onto their front porch,” Proctor said.
With experience gained from the resiliency design project added to their other studies, the student engineers graduated in the spring of 2015 and are poised to confront real world challenges.
Carlson, in fact, is still working on Chesterfield Heights—along with other regional storm water issues—on staff at the Virginia Beach office of Kimley-Horn, a nationwide engineering design and consulting firm.
“It’s been awesome to come right into the project with Kimley-Horn and Arcadis,” he said. “We are working on concept design for the National Resiliency Competition to try to win HUD grant money to make the area more resilient to flooding.”
Working on a multidisciplinary senior capstone project with professionals in the field was the perfect transition into his day-to-day work with Kimley-Horn, according to Carlson.
“[This] interests me because it’s a challenge,” says Carlson. “Every single neighborhood has different challenges—just as we found in this project.”
This story is part of an in-depth, six-part series, “Adapting to Rising Seas,” on the award-winning Chesterfield Heights resiliency design project. Stories are published every Friday and explore different aspects of the project.
