Slow-moving storms to blame for recent flooding

Slow-moving storms and higher-than-average rainfall totals are largely to blame for Western Pennsylvania's rash of landslides and flooding, officials say.

The region's numerous rivers and streams, rolling hills and valleys aren't doing it any favors.

“When you have a town that's built over a creek, you have to expect flooding,” Millvale Mayor Brian Spoales said referring to Girtys Run, which receives storm runoff from suburban areas north of the borough and flows through the heart of town.

Millvale was one of the hardest-hit communities by storms that dumped 3 to 4 inches of rain across northern Allegheny County between 6 p.m. Wednesday and 8:30 a.m. Thursday, according to the National Weather Service.

Spoales has lived in Millvale for 26 years and remembers worse flooding, including 2004 when the remnants of Hurricane Ivan dumped nearly 6 inches of rain on Sept. 17, just more than a week after Hurricane Francis remnants brought nearly 4 inches.

“Ivan wiped out the whole town,” Spoales said.

This week's storms prompted the third county disaster declaration of the year, Allegheny County Emergency Services Chief Matt Brown said.

The first was spurred by a series of landslides between February and April and the second declaration came after flooding on June 20, Brown said. The June flooding impacted 88 properties and resulted in one death, while this week's flooding likely damaged more than 20 properties but no one was injured, he said.

The disaster declaration authorizes county agencies to use all available resources and personnel necessary and to waive normal bid and contract procedures to help expedite cleanup.

Nearly 7.8 inches of rain have fallen since June 1, about 1.7 inches more than average, according to National Weather Service meteorologist Shannon Hefferan.

Hefferan said much of the rain fell during so-called training storms in which the storms remained in one place for an extended period and pelted the areas below with heavy rain, including Millvale on two occasions this week and in the South Hills on June 20.

The area should dry out over the weekend and avoid any chance of rain until Tuesday, Hefferan said.

The National Weather Service's 36-county region in Pennsylvania, Ohio, West Virginia and Maryland has recorded 57 “flood events” this year in which a storm closed roads, damaged properties and put people in danger, Hefferan said. Eighteen of them have been in Allegheny County.

The region has averaged 71 flood events a year since 1986, with the high being 320 in 2003 and the low 6 in 1988. June and July are the peak months for flash floods, records show.

“Can you ever be ready? You try to prepare as much as possible,” Millvale's Spoales said. “Somewhere over the line, it will happen again.”

Tom Davidson is a Tribune-Review staff writer.