Federal government explores a lower levee design
In 2023, after years of study, the Army Corps unveiled an early-stage plan for a 1,400-foot long, 15-foot tall earthen berm-style levee behind a row of homes along Cobbs Creek.
Army Corps officials said while the 15-foot levee would not prevent all flooding in Eastwick, it would dramatically reduce the impact of a 100-year storm, avoiding on average more than $4 million in flood damage per year to homes and infrastructure in the coming decades. But there was one problem: Army Corps modeling found that the levee would push some water up and downstream, likely causing more flooding for up to 328 structures near the Cobbs and Darby creeks in neighboring Delaware County.
Since the draft plan was released, Army Corps officials have tried to find ways to eliminate this induced flooding, but they weren’t successful, said Scott Sanderson, who leads the planning division at the Army Corps’ Philadelphia District. So they began investigating a lower levee.
The new design would follow a similar path as the previous one, but rise just 8 feet above ground level, Sanderson said.
While the original levee design would have protected against a 100-year flood, similar to the floods in Eastwick caused by Hurricane Floyd in 1999 and Hurricane Irene in 2011, the new, lower design would be less protective.
Floods like Floyd and Irene would overtop the 8-foot design, but the lower levee would still protect against smaller and more common five-year floods, like the one caused by Tropical Storm Isaias in 2020, Sanderson said.
Even the lower design is likely to cause some additional flooding in nearby places, Sanderson said. The Army Corps is now trying to determine whether that’s the case, and if so, where and how significant this induced flooding would be.
Sanderson said the multiple waterways and close proximity of homes in Eastwick makes the levee challenging to engineer.
“We’re really taking our time and looking at this thoroughly, because we don’t want to put a solution in place that moves the problem somewhere else,” he said.
It’s still not clear whether the new levee design will be built.
More analysis is needed before the Army Corps can make a final recommendation on the design, then the project would need to compete against other plans for federal funding, Sanderson said. The city would also need to sign off on the plan and raise its portion of the funding, around 35% of the total cost.
The soonest the project could begin construction would be 2030, Sanderson said.