How Forests Help Mitigate Flooding

Mar 14, 2019

Trees are big money in Virginia, generating some $21 billion each year, according to the state department of Forestry. Another $6.6 billion is attributed to forest contribution to air and water quality.

Now, the city of Virginia Beach is looking at the value of the city's forests as one solution to their flooding problems caused by climate change and the region's sinking lands.

Ironically, rain precluded a group of conservationists, scientists and Virginia Beach officials from meeting with reporters outside at one of the forests being studied in the Princess Anne District. Their biggest concern - southerly storms that not only create stormwater, but also a domino effect that pushes water from sounds to bays to tributaries and into low-lying neighborhoods.

Barbara Henley is a farmer and city councilwoman, whose family tree goes back generations in the area. She says flooding in her lifetime has been getting worse with climate change. "We're a part of the Albemarle Watershed, so we have wind tides instead of the lunar tides that the Chesapeake Bay watershed area has and when we get a prolonged southern wind we get all this water pushed up here and it can't get out until the winds shift to the north."

The city wants to consider solutions beyond stricter development regulation and expensive infrastructure flood controls like levees and tide gates.  "We're looking at all of this as part of our sea-level rise, recurrent flooding study," Henley said. "One aspect that we discovered is that we've got a lot of neat forest land. I learned how to say evapotranspiration because they taught me this process that the trees take up a lot more water than they need and it goes into the air and it can be a component in our flooding strategies.

From left: Brian van Eerden, The Nature Conservancy, director Virginia Pineland Program; Daniel McLaughlin, lead project scientist and assistant professor from Virginia Tech; Virginia Beach Councilwoman Barbara Henley
Credit Pamela D'Angelo

Virginia Tech is being brought in to study Virginia Beach and to locate forests and lands that work the hardest to reduce the risk and severity of flooding. The goal is to produce a tool that will help city officials identify best locations for reforestation and conserve forests that already sop up water.   "We're also getting evapotranspiration for unforested land uses, so we can also compare the difference what an urban system is doing - which is not much in terms of evapotranspiration," said Daniel McLaughlin, the lead scientist with Virginia Tech.

That's why urban areas with lots of roads, buildings and parking lots are referred to as heat islands. Think of a hot summer day walking across an asphalt parking lot to get into a building. Those areas can't release all that heat by evaporating water like a green space with trees and bushes can.  "Just like you perspire to cool your body, you cover the landscape. Just like you put a jacket on to take a run, you can't perspire, you can't cool yourself off," McLaughlin explained.

The city has had clashes with residents over more controversial solutions such as pumping water away from neighborhoods back into tributaries. "There is no silver bullet," Barbara Henley admitted. "One thing is not going to do everything and this idea of using trees or looking at trees is just one aspect of it. It's all a part of getting these potential tools examined."

Like many other places around the Chesapeake Bay, the city is also considering one of the most difficult solutions - migration and relocation.