A New Jersey woman caught in a flood survived a trip through its storm system, North Jersey reported. The 24-year-old DoorDash driver abandoned her car in heavy water only to be swept away under the city of Passaic and ejected into the Passaic River. Storm runoff is vital to city planning.
According to North Jersey, a woman from Newark took a risky gamble driving through a flooded street. “Nathalia Bruno, 24, was in Passaic when she attempted to drive through deep water near High Street and Benson Avenue,” the article said.
“Bruno’s car began to fill up with water and float as the tide moved it toward a large viaduct opening. Fearing the inevitable, Bruno escaped her car, but the current pulled her with the vehicle into the brook that runs below the city.”
When the Drainage System Isn’t Enough
Small amounts of rainfall can be managed with an ordinary storm drainage system, which consists of working around gravity—which will carry water downhill—and planning infrastructure such as housing to avoid consistently watery areas. However, excess rainfall can cause flash flooding, for which storm drainage systems aren’t designed.
“If all this extra water isn’t properly managed, torrents of water flowing over the road surfaces within a development are going to cause a safety hazard for drivers,” said Dr. Stephen Ressler, Professor Emeritus from the United States Military Academy at West Point. “The design engineer will address this problem by incorporating a storm sewer system into the design. A storm sewer is a network of underground pipes that collect storm water and convey it to a nearby watercourse, lake, or ocean.”
Dr. Ressler said that the water enters the storm system through aboveground inlets like curb openings and belowground inlets like precast concrete boxes with large holes to accommodate incoming and outgoing pipes—which he said are usually concrete, but steel, iron, and plastic pipes are used sometimes as well.
“The pipes themselves run from inlet structure to inlet structure arranged in a treelike network, with small branches feeding into larger trunks and these feeding into even larger main lines. All pipes in the system are placed on a steady downhill slope, so water will flow through the system by the force of gravity alone. The resulting network looks a lot like a natural river system, with the large river fed by many streams, each of which is fed by even smaller tributaries.”
Designing the Storm Sewer System
Dr. Ressler said that to design a storm sewer system, the first step is choosing appropriate locations for the aboveground inlets. They should be at the lowest point in a street; otherwise water will pool up. They should also be just uphill from intersections so water that flows along the curb won’t create a safety hazard by flowing into an intersection. Finally, extra inlets are placed at regular intervals so the inlets at the lowest points in the street don’t get overloaded.
“We still need to contend with a second major challenge—the substantial increase in discharge at the outlet,” he said. “A partial solution would be to route this discharge in a catch basin, and carry it directly to a stream through a large underground pipe. But this pipeline is only a partial solution, because dumping all this additional water into the stream will only increase the likelihood of flooding downstream.”
To combat this, engineers incorporate a storm-water detention pond into the system. A detention pond is an earthen enclosure that holds some excess water temporarily, allowing some of it to be absorbed by the soil and some of it to evaporate.
Underground systems for storm runoff are as elaborate as they are dangerous. Authorities in Passaic, New Jersey, said the woman who survived a trip through one to the outlet at Passaic River is lucky to be alive.
Dr. Stephen Ressler contributed to this article. Dr. Ressler is Professor Emeritus from the United States Military Academy at West Point and a Distinguished Member of the American Society of Civil Engineers (ASCE). A registered Professional Engineer in Virginia, he earned a BS from West Point and an MS and a PhD in Civil Engineering from Lehigh University, as well as a Master of Strategic Studies from the US Army War College.