Flooding in Glen Rock, New Jersey: two brooks, a short record, and the storms that matter
Glen Rock is not a river town in the way Lodi or Rochelle Park are. Its flood claims are few. But two brooks cross the borough, and the storms that have flooded its streets were short, violent downpours more often than long river floods.
The Bergen County 2026 Hazard Mitigation Plan maps 8.21 per cent of Glen Rock’s land in the FEMA 1 per cent annual chance flood zone, and 10.9 per cent including the 0.2 per cent zone. FEMA records 39 National Flood Insurance Program claims for the borough and one repetitive-loss property. The flood land follows Ho-Ho-Kus Brook on the east and Diamond Brook on the west, and the county plan’s event list is mostly flash floods.
The short version
- The Bergen County 2026 Hazard Mitigation Plan maps 8.21 per cent of Glen Rock in the 1 per cent annual chance flood zone.
- FEMA records 39 NFIP claims in the borough and one repetitive-loss property.
- Ho-Ho-Kus Brook runs along the eastern side and Diamond Brook through the western part of the borough.
- The flood events on record are mostly flash floods: July 2007, October 2009 and Hurricane Ida in 2021.
A modest flood zone along two brooks
Of Glen Rock’s roughly 1,739 acres, the Bergen County 2026 Hazard Mitigation Plan (Table 4.6-1) places about 143 in the Special Flood Hazard Area, 8.21 per cent. With the 0.2 per cent annual chance zone the figure is 10.9 per cent. The borough’s own architectural history describes the two watercourses behind those numbers. Ho-Ho-Kus Brook winds along the eastern side and forms part of the boundary there, and the land west of it, east of Prospect Street and south of Grove Street, is flood plain. Diamond Brook flows south through the western part of the borough toward the Passaic River in Fair Lawn.
What the FEMA claim record shows
FEMA’s National Flood Insurance Program data, grouped by community, list 39 lifetime claims for the Borough of Glen Rock. The busiest years were 1999 with 9, 2011 with 6, 2010 with 5 and 2021 with 3. By named event, FEMA attributes 8 claims to Hurricane Floyd, 6 to Hurricane Irene, 5 to the March 2010 nor’easter and 3 to Hurricane Ida. FEMA’s Multiple Loss Properties data, as of 2 August 2026, list one repetitive-loss property and none in the severe category. Against 3,696 housing units counted by the US Census Bureau, that is roughly one claim per hundred homes, by our arithmetic. The county plan counts 35 active NFIP policies in the borough as of October 2024.
Diamond Brook and Ho-Ho-Kus Brook
Both brooks are small, and that shapes how they flood. FEMA’s flood study gives Diamond Brook a drainage area of only 2.9 square miles at Harristown Road, falling to 1.8 at Rock Road. A stream that size rises and falls within hours. Ho-Ho-Kus Brook is larger: by the time it reaches Glen Rock it carries water from Franklin Lakes, Wyckoff, Allendale, Waldwick and Ho-Ho-Kus, all places where the USGS has measured it. Its Weather Service gauge at Ho-Ho-Kus, upstream, has a minor flood stage of 3 feet and major of 7, and its record crest is 7.32 feet during Floyd on 16 September 1999, when FEMA’s flood study notes a record discharge there. Irene reached 6.71 feet on 28 August 2011.
Storms the county plan remembers
The county plan’s event history records a flash flood in Glen Rock and Midland Park on 11 July 2007, when up to just over two inches of rain across the region produced widespread street flooding and one person was taken to hospital after a water rescue from a flooded underpass. On 24 October 2009, after a day of steady rain, street flooding entered a house and garage on Prospect Street. During Ida in September 2021, Patch reported that overflow from Diamond Brook and the river caused significant flooding around the Boulevard and Lowell Road and near Prospect Street, that police handled 87 storm calls, and that gas service on lower Cornwall Road and Beekman Place was shut while water was cleared from the lines.
Why basements are the likelier problem
The US Census Bureau puts Glen Rock’s median year built at 1952, and fewer than one home in ten is rented, so most residents are owners of mid-century houses with basements. When a fast storm sends water down the street faster than the drains can take it, the openings at or below ground level are where it enters: window wells, stairwells, garage doors and floor drains. Insurers treat flood, sewer backup and seepage differently.
What this means if you own or rent here
Check your address on the FEMA Flood Map Service Center, particularly if you live near Ho-Ho-Kus Brook on the east side or Diamond Brook on the west. Keep gutters and downspout outlets clear, look at whether the ground slopes toward the house, and ask a licensed plumber whether a backwater valve suits your sewer line. A standard homeowners policy excludes flood; FEMA states that a new NFIP policy normally takes 30 days to take effect. Whether a particular loss is covered is decided by your insurer and your policy wording.
Common questions
Does Glen Rock, NJ flood?
Not often, by insurance claims: FEMA records 39 in total. But the county plan maps about 8 per cent of the borough in the high-risk zone along Ho-Ho-Kus Brook and Diamond Brook, and heavy downpours have flooded streets several times, most recently during Ida in 2021.
Which streams flood in Glen Rock?
Ho-Ho-Kus Brook on the eastern side, where the borough’s history notes a flood plain east of Prospect Street and south of Grove Street, and Diamond Brook through the western part. For an individual address, use the FEMA Flood Map Service Center.
Which gauge covers Glen Rock?
The National Weather Service gauge on Hohokus Brook at Ho-Ho-Kus, upstream of the borough, with a major flood stage of 7 feet. Diamond Brook has no Weather Service forecast point.
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