What’s Causing the Flooding in Monmouth Beach?

April 9, 2018
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Flooding on Monmouth Beach roadways, like here on Central Road in September, has increased since Super Storm Sandy hit the Jersey Shore in 2012. Recent studies from outside firms found that Monmouth Beach’s storm sewer systems are undersized and outfalls into the Shrewsbury River become submerged during high tide. Photo by Jay Cook.

By Jay Cook |

MONMOUTH BEACH – Flooded roadways continue to plague residents since Super Storm Sandy wreaked havoc over five years ago.

But what has caused the increase in flooding since that historic storm? Outdated, underground stormwater sewer systems, or larger homes being rebuilt in the place of former, smaller ones?

After commissioning two separate reports last year to solve the puzzle, Monmouth Beach finally has the answer – and it lies a few feet beneath the streets.

At a borough-wide presentation on March 28, professionals from T&M Associates and Matrix New World each presented voluminous reports detailing the current state of Monmouth Beach’s underground sewer infrastructure and what, if any, impact increased impervious lot coverage from larger post-Sandy home construction had on the town.

Both firms concluded that the overwhelming source of flooding stems from Monmouth Beach’s 40- to 50-year-old stormwater sewer systems. T&M Associates found the infrastructure is often backed up from high tides, is substantially undersized and is consistently clogged with Shrewsbury River debris, causing more frequent and intense flooding.

“Monmouth Beach is always going to be a flat, low-lying community,” said Bonnie Heard, of T&M Associates, who also serves as Monmouth Beach’s borough engineer. “We can’t stop the tides. We’re just going to go ahead and do what we can and educate people.”

The flooding issue has stumped borough officials and professionals since the October 2012 storm brought in nine-foot-high storm surges and barreled through the quiet, residential community. About 74 percent of all structures and 65 percent of all properties inside Monmouth Beach lie within Federal Emergency Management Area (FEMA) boundaries for the 100 Year Flood Plain Limits.

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That proximity has had a negative effect on how effectively floodwaters are pumped out of the town. Drainage pipes in Monmouth Beach only range from four inches to 36 inches in diameter. About 44 storm sewer outfalls from the existing infrastructure head out towards the Shrewsbury River. Yet when there is a high tide, each of the 44 outfalls are submerged underwater.

Heard said that causes major backflow issues. Any rain or river water that was supposed to be on its way out of Monmouth Beach never leaves and perpetually increases.

Also compounding the problem is Monmouth Beach’s remarkably flat topography, relatively consistent with shore towns.

“Because the pipes are very flat, when the tide comes in it will bring in all types of seagrass, debris, whatever floats in,” she said. “The debris doesn’t get out of those lines as easily, like if you were in Holmdel or someplace similar, where there is a lot of slope.”

But the solution to these problems isn’t easy and could be costly. T&M Associates suggested Monmouth Beach implement stormwater sewer system upgrades into its annual capital road programs. Hardware improvements – like outfall drainage replacements and flap valves on the ends of pipes – are estimated to cost up to $1.63 million, the company found.

A figure that large could fiscally impact residents if implemented immediately, said Monmouth Beach Mayor Sue Howard. The borough instead plans to spread the work out over time.

“We have a lot of new residents following Sandy,” Howard said. “We will do everything we can do that’s appropriate on each of our streets, through a road program, to upgrade the infrastructure.”

It was also a combination of those newer residents, and the ones who decided to stay and rebuild, which influenced the other half of the reports presented last week.

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“Because the houses are bigger, people felt that it was causing problems with drainage,” said Howard. “In the end, even though the homes are bigger, the coverage has not increased significantly.”

Howard’s conclusion was reinforced by a report compiled by David G. Eareckson, president of land development services for Matrix New World, an engineering consultation firm based in Eatontown.

Eareckson was tasked with analyzing the change in impervious coverage – any surface that can’t efficiently filter or absorb water – throughout Monmouth Beach since Sandy. Increases of impervious coverage can be linked to actual increases to building size, as well as more surface area dedicated to driveways or patios.

Total impervious lot coverage in the borough grew by over 407,000 square feet compared to pre-Sandy calculations, which is a 1.7 percent jump. That equates to an increase of 346 square feet per lot in Monmouth Beach.

For a town with about 1.1-square-miles of land, it didn’t raise any red flags, Eareckson said. That would only happen if he noticed a double-digit percentage hike.

“The people in town are noticing that it’s flooding more frequently and higher than it ever used to,” he said. “It’s not the impervious coverage because it’s such a small increase.”

“At 10 percent you’d start to see impacts from it; at 20 percent we’d start to be concerned,” he added. “Anything up in the double-digits is when you start to worry.”

While the borough hashes out any future infrastructure repairs, both Eareckson and Howard suggested residents utilize water-control apparatuses at their homes. Rain barrels are popular among self-sufficient homeowners looking to save money on their water bills.

“It’s the concept of holding your water on your property – what you can do to reduce water generated from going into the storm sewers or into the streets,” said Howard.

“Every little bit helps,” she said.

For copies of the reports generated by T&M Associates and Matrix New World, visit MonmouthBeach.org and access the Floodplain Management Plan.

This article was first published in the Apr. 5-12, 2018 print edition of the Two River Times.

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