Flash flood preparation in the Black Hills
RAPID CITY, S.D. — Western South Dakota has been dry over the last several months and this sudden change in the pattern is bringing us more rain in a short span of time.
When considering issuing flood watches and warnings, meteorologists look at many factors including precipitable water which is the water in the atmosphere that is able to precipitate out, antecedent moisture conditions, or how much moisture has reached the ground and how wet the soil is, and winds aloft, which if light, could mean a slow moving storm, and prolonged rain in one place. As for areas most likely to see flash flooding, National Weather Service meteorologist Katie Pojorlie says it would be urban areas.
“Urban areas are more prone to flooding just because water can’t, there’s so much pavement that the water can’t really sink into the soil as well and there’s a lot of runoff,” said Pojorlie. “And also anywhere there’s been a fire recently, the soil’s become hydrophobic and then the water cannot sink into them as well either.”
While some may think it’s only a bit of water, it only takes a small amount to cause considerable damage. Experts say vehicles can be swept away in as little as one foot of water, and people at only six inches. It is also difficult to see roads that are lower than anticipated, or pavement not intact.
“I think it was in 2019 we had a few people find that out the hard way,” said Alexa White, the deputy director of Pennington County Emergency Management. “With going nose first, thinking they could just drive through a flooded roadway and there was no road there to drive across, it was no longer there. So they went into the rushing water and had to be rescued. Don’t let that happen to you.”
Along with watches and warnings issued by the NWS, Pennington County Emergency Management also alerts residents via sirens.
“Here we can use it for any rapidly developing life threatening situation, of which, flash floods are one of, and we probably experience more of those here in say Rapid City, than we would a tornado,” said White.
Other agencies around the Black Hills may use sirens for different situations, but you can always receive alerts from your phone through our NewsCenter1 Weather App, or a weather radio.