2018 saw record-setting rainfall. In July 2019, a month's worth of water (3.33 inches) drenched Northern Virginia in only one hour. In central Virginia this year, many neighbors are having over-the-fence discussions (when they can get outside) about the amount of rain we've been seeing and the heavier and more intense storms that have brought flash flooding and higher river levels.
If you've been thinking we've seen more than our fair share of rain of late, you are right.
The National Centers for Environmental Information, which operates within NOAA (the National Oceanic and Atmospheric Administration), has reported a trend of increasing precipitation in Virginia since 1895. In another study of 43 locations across the state by researchers at Old Dominion University, collected data shows that both average precipitation and heavy rainfall increased statewide between 1947 and 2016.
You can blame global warming for these heavy precipitation events that will only intensify and become more frequent in most regions. "At the global scale, extreme daily precipitation events are projected to intensify by about 7 percent for each 1°C of global warming," the report says.
Here's a look at Virginia's rainfall over the last 125 years.
So How Can This Hurt Homeowners?
Federal engineering standards, which affect stormwater infrastructure, are based on rainfall projections. These projections are themselves based on data collected by the National Weather Service known as Atlas 14 reports. Disturbingly, the last time this data was updated was 2006.
According to State and local officials, Atlas 14 projections have historically been low, by as much as 20% in some locations. Couple this with the higher rainfall figures over the past ten years, and bridges, floodwalls, and stormwater gates are at a much greater risk of damage from stress. Culverts and curb inlets built to handle less runoff cannot handle the increased flow, leading to more incidents of nuisance flooding and wastewater backup.
These aren't the only threats, however. Overwhelmed systems can cause many other problems. In Richmond, Alexandria, and Lynchburg, where century-old combined sewer systems channel stormwater through the same pipes that carry wastewater, high-intensity rains can lead to overflows of raw sewage into waterways or backed up into homes. Norfolk's struggling stormwater system has led to more frequent road closures, limiting access and quick response for emergency services like EMTs and fire departments.
Here's How Homeowners Help
Run off is one of the major ontributing factors to flash flooding, street closures, and stormwater system failures.
Here are some of the steps homeowners can take to help mitigate runoff:
· Use permeable surfacing like gravel or pavers for driveways, walkways, and patios.
· Install rain gardens for downspout areas.
· Use rain barrels for downspouts.
· Keep grass cut at 3" high. This reduces the need for watering and increases ground absorption.
· Increase plantings. More plants means more roots to absorb water.
· Install a dry well - usually a plastic container with holes buried underground to collect water and
allow slow absorption into groundwater.
· Direct stormwater flowing through your property into catch areas.
Sources: Washington Post, Virginia Mercury, NOAA