Why the Hackensack River floods: New Milford, Hackensack, Teaneck and Ridgefield Park
The Hackensack behaves like two different rivers. Which one you live beside decides what kind of flood you get, and which forecast is worth watching.
The upper Hackensack is held back by four water-supply reservoirs, and the towns just below the last of them, New Milford and River Edge, flood when heavy rain meets storage that is already full. Further south the river is tidal, and FEMA attributes the principal flooding to the tides of Newark Bay. Hackensack and Ridgefield Park add a third ingredient, combined sewers. This guide sets out what the gauge records, the FEMA flood study and the county hazard plan show for each stretch.
The short version
- The Hackensack is tidal up to Oradell Dam. FEMA attributes the principal flooding in southern Bergen County to the tidal stages of Newark Bay.
- Upstream flow is regulated by four water-supply reservoirs operated for municipal supply. FEMA records that the lower river and Pascack Brook flood when Oradell Reservoir is at a high stage.
- The flood of record at New Milford is 12.36 feet on April 16, 2007; major flood stage there is 10.0 feet.
- New Milford has 49 severe repetitive loss properties in the county plan, the highest figure printed for any Bergen municipality.
- Hackensack and Ridgefield Park have combined sewers that discharge during heavy rain, so floodwater there may contain sewage.
- About 24 per cent of Ridgefield Park and 18 per cent of Hackensack lie in the FEMA one per cent annual chance flood zone.
Two rivers in one
The Hackensack River drains a watershed of 197 square miles in northeastern New Jersey and southern New York, on a course of about 50 miles that ends at Newark Bay. The US Fish and Wildlife Service describes three quarters of that watershed as urbanised. What divides the river is Oradell Dam. The Army Corps of Engineers describes the Hackensack as tidally influenced up to Oradell Reservoir, so the river that passes Hackensack, Teaneck, Bogota and Ridgefield Park rises and falls with the tide. Upstream, the flow is controlled by storage. The USGS gauge at New Milford, below the reservoir, where the drainage area is 113 square miles, carries the remark that flow is regulated by DeForest Lake, Lake Tappan, Woodcliff Lake and Oradell Reservoir, operated by Veolia Water for municipal supply. The state water supply plan gives Oradell Reservoir a storage capacity of 3.507 billion gallons and calls it the terminal impoundment of that system. Those two facts, a tidal lower river and a supply of water from upstream that is governed by reservoirs, explain almost everything that follows.
Below the reservoir: New Milford and River Edge
At the New Milford gauge the National Weather Service sets action stage at 5.5 feet, minor flood stage at 6.0, moderate at 8.0 and major at 10.0. The flood of record is April 16, 2007, at 12.36 feet and 11,600 cubic feet per second. Second by stage is September 16, 1999 (Floyd) at 11.45 feet. FEMA ranks by flow and puts Irene second at 10,500 cubic feet per second, ahead of Floyd at 9,760. The NWS impact statements name the same four New Milford streets at every level: minor flooding along Columbia Street, Harvard Street, Pine Avenue and Lenox Avenue at 6 feet, water into homes there at 8 feet, and evacuations at 10 feet. FEMA addresses the role of storage. Its flood study states that the lower portions of the Hackensack River and Pascack Brook flood when Oradell Reservoir is at a high stage, gives the spillway crest as 22.7 feet, and records a peak reservoir elevation of 26.2 feet on September 17, 1999. After flooding in April 2022, the state environmental department said, as reported by CBS New York, that Oradell serves as a water supply reservoir and that the dam was not built for flood control purposes.
What that has cost New Milford
The county hazard plan shows how concentrated the damage in New Milford has been. Only 13.80 per cent of New Milford lies in the FEMA one per cent annual chance flood zone, yet the plan lists 797 flood insurance losses there as of October 2024, more than in the city of Hackensack. In the repetitive loss table New Milford has 49 severe repetitive loss properties, the highest figure printed for any municipality, and repetitive loss payments of about 22.4 million dollars. The plan names New Milford and River Edge among the municipalities where repetitive loss properties are concentrated. River Edge has 10.67 per cent of its land in the flood zone and 103 recorded losses; Oradell has 9.70 per cent and 35. One caution on these figures: the county totals printed beneath the plan's insurance tables do not match the sum of the rows, so this guide quotes individual rows as printed and does not rely on the totals.
Further south: the tide decides
For the river further south, FEMA's flood study is unambiguous: the principal flooding in southern Bergen County results from the tidal stages of Newark Bay, which affect the Hackensack and Passaic rivers. The county plan lists the municipalities exposed to coastal surge on the Hackensack, among them portions of the City of Hackensack, portions of Teaneck, portions of Ridgefield Park and all of Bogota. The National Weather Service keeps a record of what specific tide levels at Bergen Point have done, measured in feet above mean lower low water. On October 27, 2018, at 8.9 feet, West Fort Lee Road along the river in Bogota was closed and a car was left stranded at the river end of Bergen Turnpike in Ridgefield Park. On December 23, 2022, at 9.1 feet, the record notes River Street flooded and closed and water rescues on South Newman Street, which it attributes to a combination of one and a half to two inches of rain and surge up the Hackensack River. The benchmark is Hurricane Sandy: 14.6 feet at Bergen Point on October 29, 2012, with FEMA noting that less than two inches of rain fell in Bergen County. That was a flood made almost entirely of tide.
A third ingredient: combined sewers
Hackensack and Ridgefield Park have something most Bergen towns do not. The Bergen County Utilities Authority states that Fort Lee, Hackensack and Ridgefield Park have drainage areas with combined sewer systems that discharge into local waters during heavy rainfall. In a combined system, stormwater and sewage share one pipe. A 2014 state bulletin recorded two active combined sewer outfalls in Hackensack and six in Ridgefield Park; the village says four of its six discharge to the Hackensack River and two to Overpeck Creek. The City of Hackensack links these systems to street flooding as well as to pollution, and in February 2025 it announced a compliance agreement with the state, Fort Lee, Ridgefield Park and the utilities authority. The city reports that some separation projects have already been completed and have reduced flooding, and the county plan describes a large sewer separation project. The authority cautions that the full long-term control plan may take 25 to 30 years to implement. For a property owner the point is practical. Water that backs up in these areas during heavy rain may contain sewage, which makes it a health hazard and a job for trained crews rather than a mop.
How much of each town is mapped as flood zone
The county plan gives the share of each municipality inside the FEMA one per cent annual chance flood zone, with the wider figure that adds the 0.2 per cent zone in brackets. Ridgefield Park: 24.03 per cent (24.92). Hackensack: 17.96 (19.97). New Milford: 13.80 (16.85). Bogota: 12.54 (13.07). River Edge: 10.67 (13.46). Teaneck: 9.80 (10.81). Oradell: 9.70 (11.85). The insurance record follows a similar order. As printed in the plan, Hackensack has 483 active flood policies, 504 losses and 75 repetitive or severe repetitive loss properties; Ridgefield Park has 210 policies, 246 losses and 47 such properties; Teaneck has 98 policies, 109 losses and 11. These are whole-town figures and say nothing about a particular address. One gap is worth stating. No official source reviewed for this guide gives a Sandy surge height or a street-level damage record for Hackensack, Teaneck or Ridgefield Park specifically, so none is quoted here.
What has been proposed, and what has been built
The largest proposal is federal. The Army Corps of Engineers' New York and New Jersey Harbor and Tributaries study examined storm surge barriers across the region, including one on the Hackensack River, and in 2022 put forward a comprehensive plan costed at 52.7 billion dollars. In July 2025 the Corps published an interim report recommending three smaller actionable elements at about 1.07 billion dollars. None of the three is on the Hackensack, Teaneck or Ridgefield Park stretch of the river. Locally the picture is incremental. The county plan records Hackensack's sewer separation work, a borough-wide flood warning system completed in Oradell, and Teaneck's plan to extend its warning siren and speaker system. For Bogota it lists a stormwater problem at Elm Avenue and River Road with the note that no progress has been made yet. Nothing in these records describes a structure, built or funded, that would keep a Sandy-scale tide out of the lower river.
What this means if you own property here
Start by working out which kind of flood your stretch of river produces. In New Milford and River Edge, the thing to watch is the New Milford gauge and the rainfall forecast, bearing in mind FEMA's note about flooding when the reservoir is at a high stage. Further south, watch the coastal flood forecast and the tide times: FEMA attributes the principal flooding there to tide, and the 2022 rescues in Hackensack came from ordinary rain arriving on a high tide. In Hackensack and Ridgefield Park, assume that water rising from drains in heavy rain may be contaminated. Wherever you are, stay out of standing water until the electricity is confirmed off. Flood is a separate policy from homeowners insurance, and FEMA states a new policy normally takes effect 30 days after purchase. Whether an individual address sits in a mapped flood zone is something only the FEMA Flood Map Service Center can answer.
Common questions
Is the Oradell Reservoir supposed to prevent flooding?
No. USGS records that the reservoirs on the Hackensack are operated for municipal water supply. After the April 2022 flood the New Jersey Department of Environmental Protection said, as reported by CBS New York, that the Oradell Reservoir serves as a water supply reservoir and that the dam was not built for flood control purposes. FEMA notes that the river below floods when the reservoir is at a high stage.
Why does Hackensack flood when it has not rained much?
Because the river there is tidal. FEMA attributes the principal flooding in southern Bergen County to the tidal stages of Newark Bay, and the county plan lists portions of Hackensack as exposed to coastal surge. The National Weather Service recorded water rescues on South Newman Street in December 2022 from under two inches of rain combined with surge up the river.
Which streets flood first in New Milford?
The National Weather Service impact statements for the New Milford gauge name Columbia Street, Harvard Street, Pine Avenue and Lenox Avenue. Minor flooding begins there at 6 feet, water enters homes at 8 feet, and evacuations are noted at 10 feet. These are the weather service's published descriptions for the gauge and are not a statement about any single property.
Is a flood barrier planned for the Hackensack River?
A storm surge barrier on the Hackensack was among the measures studied by the Army Corps of Engineers in its regional harbor study, whose 2022 plan was costed at 52.7 billion dollars. The interim report the Corps published in July 2025 recommends three smaller projects, none of them on the Hackensack, Teaneck or Ridgefield Park stretch of the river.
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