It’s an increasing problem in New Jersey, especially now that it’s getting warm.

And sometimes it can even be deadly.

The risk of dangerous flash flooding is on the rise, according to the New Jersey state climatologist at Rutgers University, Dave Robinson.

Flash flooding can result from 1 to 2 inches of rain in an hour.

“It can swamp cars at intersections, underpasses, and it can sweep cars and people away if they get in the fast moving water," Robinson says.

Robinson noted we are seeing an increased risk of flash flooding because rain storms tend to be more intense now than they used to be, and also more of the ground is now covered by streets, roads and parking lots than at any time in the past.

“Water in an urban or suburban area has no time to soak into the ground. As a matter of fact, there’s no ground for it to soak into in some places,” he said.

“It comes off the rooftops, it comes out of parking lots, and it can accumulate very rapidly. So these are extremely dangerous and deadly situations.”

Robinson pointed out back in the 1970s there was a sudden flash flood in the Green Brook and Bound Brook basin areas in Central Jersey. The 1973 flooding killed six Green Brook residents.

He noted a flash flood along Route 22 a few years ago took down retaining walls and flooded the highway, but fortunately there were no fatalities.

“The problem has gotten worse over time in New Jersey as we’ve increased the amount of impervious surfaces.”

Robinson said flashing flooding can be a problem at any time of year, but the danger level is rising.

“You’re more likely to see it during the summer because that’s when we get our flashier rain storms, our downpours from thunderstorms.”

He explained said this can also be a problem during the winter, especially when drainage areas become blocked by snow and ice, and during the fall when drainage basins may be blocked by leaves.

“The threat is always there, but generally it’s summer thunderstorms, where you get an inch or multiple inches of rain in just an hour or two that lead to the most dangerous and deadly flash flooding,” he said.

Robinson stressed you might not think a couple of inches of water could pose a serious risk, but it can.

“We’re talking about a deadly situation both if you’re in a vehicle or walking,” he said.

“You can very quickly be knocked off your feet by moving water, and it doesn’t take more than 6, 8, 10 inches of fast moving water to lead to you losing control of your vehicle.”

You can contact reporter David Matthau at

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