‘Royal tide’ hits Hampton Roads this weekend, leading to flooding – and citizen scientists – The Virginian-Pilot

Expect flooding this weekend, Hampton Roads.

It’s the time of what’s known as the “royal tide,” or one of the highest tides of the year, when the Earth, Moon, and Sun align.

At the Sewell’s Point tide gauge in Norfolk, the tide could be 4 to 5 feet above normal low tide on Saturday, said Skip Stiles, executive director of Norfolk-based Wetlands Watch. The waters will peak shortly before 11 a.m.

This means floodwaters are sitting on the streets in the usual places. Water levels will likely be comparable to recent flooding in late October, Stiles said.

High tides can occur several times a year, said Margie Mulholland, professor of oceanography at Old Dominion University and wife of Stiles.

A spring tide – not named for the season but the “springing” tide occurs twice a month and brings the strongest gravitational force. A royal tide is when it coincides with the point of the moon’s orbit being closest to the Earth, exerting even more gravitational pull.

This weekend will see even more flooding due to strong projected northerly winds pushing more water through the mouth of the Chesapeake Bay, Mulholland said.

With the royal tide comes the annual citizen science event Catch the King. It started in 2017 as a low-cost way to collect flood data, Stiles said.

“We wanted to get better information into the hands of decision makers about where the floods were actually happening,” he said. “Not just, ‘Hey, there’s flooding at this intersection,’ but the extent.”

Armed with waders and the Sea Level Rise phone app, volunteers circle the floodwaters, dropping GPS data that draws a virtual outline of each site. The pandemic put an end to the event last year, but a few hundred citizen scientists will be present in flood-prone areas, including The Hague.

A revamped app will be ready soon, Stiles said. They hope to expand to rural areas of coastal Virginia where officials need more flood data as they plan for sea level rise. Mulholland, meanwhile, is leading a separate project called Measure the Muck.

During the first event in 2017, she said she noticed feces and other sludge floating in the floodwaters as it receded. As a member of the Chesapeake Bay Program Committee overseeing pollution control programs, she realized that floodwaters were not being considered.

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Every year, she leads a team that collects water samples during the high tide to measure the nutrients inside.

What they found: During a flood on a sunny day, the water contained the maximum amount of nitrogen that was supposed to be allowed for an entire year for the Lafayette River. Allowances are outlined for bay restoration efforts.

“It was quite shocking for us,” she said.

Traditional runoff, from agriculture or treated sewage, for example, tends to move in one direction. Floodwaters are different because they sit on the ground for a while, picking up whatever is there, Mulholland said.

Measure the Muck also found high levels of bacteria associated with animal feces in the water. Don’t let children play in the water, she advised.

On Saturday, participants will travel along the Lafayette River, taking samples of floodwater one 200 millimeter bottle at a time.

Katherine Hafner, 757-222-5208, [email protected]

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