by the Center for NYC Neighborhoods
This is one of the least expensive mitigation options available, but it is only an option in homes where the mechanical utilities and controls are above, or able to be relocated above, a specific height called the Design Flood Elevation. If you want to install flood vents or openings, any area below the Base Flood Elevation must be used only for parking, storage, or building access, and the area below the BFE must have at least one side that is at or above ground surface.
Installing flood vents lower your flood insurance premium if at least one side of the floor of your basement or crawl space is at or above ground level, or if it is done in tandem with filling in your basement or crawl space to ground level. In high-risk flood zones, the primary factor in determining your insurance rate is the difference between the elevation of the lowest floor in your home and the BFE. If you fill in your basement and install flood vents, the next highest floor becomes your “lowest-floor,” which will lower your insurance premium.
By adding openings to the side of your building, you reduce the risk of damage from water pressure (hydrostatic and hydrodynamic forces). In the event of a flood, water can flow into and out of your home freely through the vents, with no need for human intervention, which will reduce the risk of structural damage to your walls or foundation.
If your utilities are already above the Design Flood Elevation and you do not have a basement or crawlspace to fill in, installing flood vents is relatively easy, and shouldn’t take more than a few days. If you do need to fill in a basement or crawlspace and/or raise mechanical equipment, wet floodproofing will be more complicated, time consuming and costly.