Flooding in Hillsdale, New Jersey: the flood zone, the record, and what to do
Hillsdale sits directly below one of the county's high hazard dams, with Pascack Brook running out of the Woodcliff Lake reservoir and through the borough. The flood record that follows is one of the heavier ones in northern Bergen County.
FEMA counts 399 National Flood Insurance Program claims in Hillsdale, the thirteenth-highest total of Bergen County's 70 municipalities, and lists 49 repetitive-loss properties, 21 of them severe. The Bergen County 2026 Hazard Mitigation Plan puts 11.25 per cent of the borough's land in the 1 per cent annual chance flood zone. Hurricane Irene, Hurricane Floyd and the April 2007 nor'easter account for most of the claims, and the borough is now using the state's Blue Acres programme to buy out some of its most often flooded homes.
The short version
- FEMA records 399 flood insurance claims in Hillsdale, the thirteenth-highest total in Bergen County.
- FEMA lists 49 repetitive-loss properties in the borough, 21 of them severe, as of August 2026.
- The Bergen County 2026 Hazard Mitigation Plan puts 11.25 per cent of Hillsdale's land in the 1 per cent annual chance flood zone.
- The Woodcliff Lake reservoir above the borough is a water supply reservoir, not a flood-control structure.
- The state has listed 10 Hillsdale properties for voluntary Blue Acres buyouts; six had closed or were being acquired by early 2025.
The flood zone and the claims, side by side
Table 4.6-1 of the Bergen County 2026 Hazard Mitigation Plan measures 211.22 acres of Hillsdale, or 11.25 per cent of its land, in FEMA's Special Flood Hazard Area, rising to 13.75 per cent with the 0.2 per cent annual chance zone included. FEMA's National Flood Insurance Program data record 399 claims over the life of the programme. Against the 3,602 housing units the US Census Bureau counts, that is roughly 111 claims per 1,000 homes by our arithmetic, the eighth-highest rate in the county. The worst year was 2011, with 132 claims, then 1999 with 68, 2007 with 54 and 2021 with 35. By named event, FEMA attributes 75 claims to Hurricane Irene, 65 to Floyd, 52 to the April 2007 nor'easter and 32 to Ida. FEMA's multiple-loss file, as of 2 August 2026, lists 49 Hillsdale properties as repetitive-loss, 21 of them severe.
A borough below a reservoir
FEMA's countywide Flood Insurance Study places the Woodcliff Lake reservoir on Pascack Brook in the Borough of Hillsdale, and the state lists the Woodcliff Lake Dam as a high hazard potential dam in Hillsdale. That classification describes the consequences if a dam failed, not its condition. The study notes that the reservoir and Lake Tappan steady the Oradell Reservoir and have a natural damping effect on most flood peaks, but that they are owned and run for public water supply and are not designed or used for flood control. The reservoir's spillway crest is 94.0 feet; its highest recorded level was 97.65 feet on 2 February 1973. When the lake is full, rain arriving upstream passes over the spillway into the brook that runs through town.
More than one stream
Pascack Brook is the main flood source, but it is not the only one. FEMA's flood study includes Hillsdale Brook in the borough, a small stream that flows to Holdrum Brook, and the Musquapsink Brook runs south through Hillsdale into Washington Township on its way to Westwood. Each has its own mapped floodplain, so being well away from the Pascack does not on its own put a house out of reach of water. Storm drainage matters too: the county plan records that a July 2002 thunderstorm, with rainfall rates of one to two inches an hour, left up to two feet of water at the Hillsdale Toll Plaza on the Garden State Parkway. Flash flooding of that kind can happen far from any mapped stream.
The floods residents remember
The county plan describes Tropical Storm Andrea in June 2013, when Pascack Brook flooded multiple streets in Hillsdale and the gauge downstream in Westwood rose above its 5-foot flood stage to crest at 5.27 feet. That was a small flood by local standards. Floyd in 1999 and Irene in 2011 were far larger on the same brook, and the April 2007 nor'easter came close behind in the claim count. Ida in September 2021 added 32 more, a reminder that the record is not only a story of the 1990s and 2000s.
Buyouts and warnings
Hillsdale's entry in the county plan reports a new flood warning siren, updated communication plans for residents in flood-prone areas, a mass alert system, and several homes taking part in the Blue Acres programme. It also commits the borough to work with Veolia, the water company, on managing the reservoir and its levels. In March 2025 Pascack Press reported that the council approved an agreement with NJDEP endorsing Blue Acres, after the state listed 10 Hillsdale properties on Beechwood Drive, Hazelwood Avenue, Sycamore Avenue, Glendale Drive and Riverside Drive. According to the borough administrator, six were closed or being acquired; the other four owners chose not to sell. Participation is voluntary, and bought-out land is kept as open space.
What this means if you own or rent here
The county plan counts only 67 active flood policies in Hillsdale as of October 2024, fewer than one for every 50 homes in a borough with 399 claims on record. If you live near Pascack Brook, Hillsdale Brook or the Musquapsink, check your address on the FEMA Flood Map Service Center and price a policy before you need it; FEMA states that a new policy normally takes 30 days to take effect. Sign up for the borough's emergency alerts and learn where your street sits relative to the brook. Most Hillsdale homes are owner-occupied, and the US Census Bureau puts the median year built at 1959, so many basements predate modern drainage standards. Whether a particular loss is covered is decided by your insurer and your policy wording.
Common questions
Does Hillsdale, NJ flood?
Yes. FEMA counts 399 flood insurance claims in Hillsdale, most of them from Hurricane Irene, Hurricane Floyd and the April 2007 nor'easter, and the county plan puts 11.25 per cent of the borough in the 1 per cent annual chance flood zone.
Does the Woodcliff Lake reservoir protect Hillsdale from floods?
Only partly. FEMA's flood study says the reservoir has a natural damping effect on most flood peaks, but it is run for water supply and is not designed or used for flood control. When it is full, storm water passes over the spillway into Pascack Brook.
Can I sell my flooded Hillsdale home to the state?
The NJDEP Blue Acres programme buys flood-prone homes from willing sellers, and Hillsdale has signed an agreement endorsing it. Eligibility depends on the property, so ask the borough and Blue Acres directly; participation is voluntary.
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