ISSUE: How Do Engineers Know What to Place and Where Along the City’s Stormwater Infrastructure?

FACT: Engineers use computer modeling to simulate the impacts of a storm throughout our city to determine how existing infrastructure can handle a storm, and how changes or upgrades will impact specific neighborhoods as well as the overall system.
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It’s important to keep a few things in mind when talking about stormwater in Virginia Beach. The first is that all of our waterways empty out into a tidally influenced body of water like the Atlantic Ocean, Chesapeake Bay or Back Bay which experiences wind tides as opposed to lunar tides. Since sea levels have risen about a foot over the past 50 years, this has had an impact on how much water our existing infrastructure can remove from the system. So, it’s up to us to help nature along.

It’s not a simple matter of installing bigger pipes or a big pump to move the water along. Each of the 31 drainage basins in Virginia Beach are connected, either through natural means such as canals and ditches or man-made means like storm drain pipes. Installing larger pipes or pump stations could help an individual neighborhood, but could cause significant issues up and downstream. This is why engineers evaluate the best course of action to improve a neighborhood’s resiliency to recurrent flooding.

Once engineers determine what needs to be done, projects are prioritized based on a number of factors, such as the overall impact to flood resiliency and public safety. The projects are then brought to City Council for consideration and funding.

Money is certainly a limiting factor in completing projects, but not the only one. The plan as it stands is to have the identified infrastructure improvements completed within the next 15 years. There are a few reasons that it takes this long. First and foremost is the impact on neighborhoods. Projects that involve going into a residential area are typically done in 1,000-foot segments to limit the impact on those who call that neighborhood their home. If an entire subdivision was torn up, residents would be living in a construction zone for a year, assuming they could even access their home at all.

Another consideration is the permitting process, especially when federal waters are involved. The larger the impact on the waterway, the longer the approval process can take – sometimes more than a year. 

It is a lengthy process, but one the City is committed to seeing through to harden our neighborhoods against sea level rise and recurrent flooding. Throughout the 15 years of projects, residents can expect to see improvements as work progresses through the neighborhoods. Most recently, the City weathered Hurricane Dorian with no major flooding or loss of any homes. Projects in Windsor Woods, Princess Anne Plaza and The Lakes, such as canal dredging and storm drain cleaning, have improved the ability for the stormwater system to remove water from those neighborhoods. 

In the Cape Henry canal, Public Works staff was able to close a sluice gate to keep water from coming in with the tide. More specifically, during the storm, the upstream water surface elevation at the West Great Neck Road sluice gate was held at 3.24 Ft while the downstream water surface elevation rose to elevation 4.34 Ft.  Thus the upstream area (Cape Henry Dr.) was protected from an extra 1 foot of flooding water.
The projects are being built with a 100-year storm in mind. That is a storm that has a 1% chance of occurring in any given year. In such a storm, the goal is to keep the water away from homes and businesses by draining the water away faster and also ensuring that roads are passable. Keep in mind that streets are part of the stormwater system – they hold water before it’s carried away. 

For more information about ongoing projects and quarterly updates in Virginia Beach, please visit the Stormwater Engineering Center website​. A list of projects and information can be found there. Updates are provided to City Council every three months. Videos of the briefings from 2019 can be found in the sidebar to the right, and copies of the PowerPoint presentations are available on the Stormwater Engineering Center website listed above.

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