Study: New Parkway Interchange Had ‘Minimal’ Effect in 2018 Greenbriar Flood

Flooding in Greenbriar I, Aug. 13, 2018, captured by a Brick police drone. (Credit: Brick Twp. Police)

A study commissioned following a catastrophic flooding event in Brick Township’s Greenbriar community has determined that the new Garden State Parkway interchange 91 had “minimal” effects on the outcome.

Ocean County, which designed the new interchange and improvement along Burrsville Road, paid for the study, performed by French & Parrello Associates. It was recently completed and forwarded to the county engineer’s office as well as Brick officials. Greenbriar, an age-restricted community off Burnt Tavern Road, backs up to Burrsville Road, which in turn borders the Parkway’s northbound lanes. Dozens of homes in the community were flooded in the freak Aug. 13, 2018 storm, which dumped nearly 8-inches of rain on the township in a matter of two hours.

Among the study’s findings:

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• The Parkway’s road surface is about 5-feet higher than the westerly section of Greenbriar. Any backup in the Parkway’s drainage culverts due to severe rainfall would, indeed, result in flooding in Greenbriar, however this flooding would have occurred even if the new interchange was never constructed.
• After a study of hydrological patterns compared with a review of Brick police drone video taken in the immediate aftermath of the flooding, the researchers concluded that some runoff from the highway’s northern drainage culvert overflowed and streamed to the southern culvert. The storm itself, without even accounting for any overflow from the north culvert, resulted in double the normal rainstorm flow to the southern culvert – the one which has the potential to cause flooding in Greenbriar. The water was running at a staggering 352 cubic feet per second.
• The Burrsville Road improvement had no effect on the flooding, while the Parkway interchange improvements may have had a “minimal” effect on the flooding – but flooding would have occurred regardless of the new interchange being constructed.

The study did find, however, that there was some blockage of flow at the bank of the northern drainage culvert, though improvements were made to these areas after the Aug. 2018 rainfall event.