While meteorologists reported a record overall 5.96-inch rainfall over a 24-hour period throughout the Pittsburgh region last Friday, the 3 Rivers Wet Weather rain gauge system recorded complete rainfall data for each of the communities throughout Allegheny County.

According to this sophisticated rain gauge system, more than half of the communities across the County were pummeled with at least 5.5 inches of rain while some communities in the western part of the County, such as Moon Township, North Fayette, Findlay, Collier, Bridgeville and Kennedy Township were hit with nearly eight inches from 4 a.m. Friday morning until the rain tapered off at 1 a.m. Saturday.

Rainfall data is collected through a network of 33 rain gauges strategically placed based on localized storm patterns and areas that are difficult for the radar to detect, such as hillsides, tall buildings and valleys. The data is then calibrated with the NEXRAD radar coverage area using specialized software. This calibration fills in the gaps between rain gauges and determines the virtual rainfall specific to each square kilometer (.4 square miles) in Allegheny County.

“The resulting data is so accurate, it’s equivalent to having a total of 2,275 rain gauges throughout the region,” said John Schombert, executive director of 3RWW.

As a non-profit organization charged with helping 83 municipalities in Allegheny County address the region’s aging and deteriorating sewer infrastructure, 3RWW developed the rain gauge network to help municipal engineers plan and design effective sewage and storm water control solutions in their communities. Accurate rainfall data helps determine how much rainfall a community is likely to experience over a given period of time and how its sewage system functions during a storm.

“This is extremely important information,” said Schombert, “because an error of as little as 10 percent on rainfall amounts when designing a storm water control basin, for example, could mean wasted money or an ineffective solution.”

Rainfall data is available via the 3 Rivers Wet Weather website where a near real-time section demonstrates the rainfall occurring over the last six hours (with a 15-minute delay) in the form of a color-coded map, and a historical section shows data collected for previous months, beginning in 2000. A beta site is being tested to access the current month’s specific data via a color-coded map and chart showing actual rainfall amounts.

NewsClip: Highest Rainfall Didn’t Always Add Up to Heaviest Flooding

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Keep Pennsylvania Beautiful

GreenTreks Networks

Lancaster Farmland Trust

9/24/2004