New Jersey Water Science Center
Bound Brook at Middlesex, NJ Flooding New Jersey Flood Links
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Summary of Flooding in New Jersey Caused by
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In the Raritan River Basin, flood peaks were the highest ever recorded at 8 of the 23 long-term gages. Two of these stations—South Branch Raritan River near High Bridge (01396500) and Millstone River at Blackwells Mills (01402000)—recorded the highest peaks in more than 90 years of record. The peak stage at the Stony Brook at Princeton (01401000) was nearly 2 feet higher than the previous record.
The gage on the Elizabeth River (01393450) and the two gages on the Rahway River at Springfield (01394500) and Rahway (1395000) recorded peaks of record for 89, 73 and 89, years of record, respectively. The peak stage at the Rahway River at Rahway was 2.5 feet higher than the previous peak of record.
Figure 9. Screen capture of hydrograph showing record high stage on August 28, 2011, at the continuous-record streamflow-gaging station on the Crosswicks Creek at Extonville, NJ (U.S. Geological Survey station 01464500).
Along the Delaware River tributaries north of Trenton, four of the nine long-term gages recorded peaks of record. Records were set at the Musconetcong River at Bloomsbury gage (01445000), the Flat Brook near Flatbrookville gage (01440000), Assunpink Creek at Trenton (01464000), and Pequest River at Huntsville (01445000) which have 94, 88, 88 and 31 years of record respectively. Four more gages on these tributaries recorded the second highest peaks of record. Along tributaries to the Delaware River in the Coastal Plain, 5 of the 14 long-term gages recorded peaks of record. The peak stage at the Crosswicks Creek at Extonville (01464500) was 3.2 feet higher than the previous peak of record (fig. 9). Four other gages on tributaries to the Delaware River in the Coastal Plain recorded the second highest peaks of record.
Figure 10. Flooding at streamflow-gaging station on the Toms River near Toms River, NJ (U.S. Geological Survey station 01408500), after the peak on August 29, 2011. (Photograph by Brian Painter, U.S. Geological Survey)
In the Atlantic coastal drainages, 5 of 14 long-term gages recorded peaks of record. The record peak at the Toms River gage was the highest in 82 years of record (fig. 10). Three other gages recorded the second highest peaks of record.
Statewide thirty-three gages recorded peaks greater than the 100-year recurrence interval (< 1.0% annual exceedance probability). Flood frequencies observed during this flood exceeded the 100-year flood frequency at gages in the Hackensack River, Passaic River, Elizabeth River, Raritan River, Manasquan River, Toms River, Maurice River, Rancocas Creek, Cohansey River, Musconetcong River, Raccoon Creek, and Salem River Basins (table 1).
Gages along the main stem of the Delaware River recorded only 4- to 6-year flood events (17–25% annual exceedance probabilities) during the hurricane. The gages on the Cedar Creek (01409000) and Westecunk Creek (01409280) recorded only 2-year events. The gage on East Branch Bass River near New Gretna (01410150) recorded less than 2-year events (>50-percent annual exceedance probability). The flood frequencies associated with these flood peaks are referenced from Watson and Schopp (2009) and Schopp and Firda (2008) . The flood frequency statistics for this flood are considered provisional and may change upon reanalysis.
The New Jersey Department of Environmental Protection (NJDEP) Bureau of Dam Safety reported the failure of six dams as a result of this storm. Three of these dams are located upstream from USGS gaging stations. Saffrin Pond Dam, failed completely. It is located on Weldon Brook, a tributary to Lake Hopatcong, upstream from the USGS stage-only gage on Lake Hopatcong and the continuous-record streamflow-gaging station on Musconetcong River at the outlet of Lake Hopatcong. The New Jersey No Name # 89 Dam, located on a tributary to Crosswicks Creek in North Hanover Township in Burlington County upstream from the gage on Crosswicks Creek at Extonville, failed completely. The Bureau of Dam Safety also reported damage to the spillway at Cassville Dam, located on a small tributary to the Toms River, upstream from the gage on Toms River near Toms River. Water stored in these impoundments contributed to the flow past these gages during the flood. The portion of the hydrograph contributed by the dam breaches is not distinguishable from the runoff contributed by the rainfall.
The NJDEP Bureau of Dam Safety reported the failure of five dams as a result of the storm on August 14. The Seeley’s Mill Pond Dam located upstream from the Cohansey River at Seeley gaging station failed completely.
Peak stage during high tide on Sunday morning, August 28, 2011, was the highest for the period of record at six USGS continuous-record tide-telemetry stations. The five gages with new record high peaks are Passaic River at PVSC at Newark (01392650), Raritan Bay at Keansburg (01407081), Shrewsbury River at Sea Bright (01407600), Shark River at Belmar (01407770), and Manasquan River at Point Pleasant (01408050). The datum of these gages is North American Vertical Datum of 1988.
Figure 11. Hydrograph showing record high stage on August 28, 2011, at the continuous-record tidal stage gage on the Shrewsbury River at Sea Bright, NJ (U.S. Geological Survey station 01407600)
The gage at Passaic River at PVSC, at Newark recorded a peak stage of 7.11 feet, 0.64 feet higher than the previous peak of record on March 13, 2010. The gage at Raritan Bay at Keansburg recorded a peak stage of 7.16 feet, 0.15 feet higher than the previous peak of record on March 13, 2010. The gage at Shrewsbury River at Sea Bright recorded a peak stage of 6.29 feet, 0.96 feet higher than the previous peak of record on March 13, 2010 (fig. 11). The gage at Shark River at Belmar recorded a peak stage of 5.98 feet, 0.39 feet higher than the previous peak of record on March 13, 2010. The gage at Manasquan River at Point Pleasant recorded a peak stage of 5.80 feet, 0.93 feet higher than the previous peak of record on March 13, 2010.
The New Jersey Department of Environmental Protection (NJDEP) Bureau of Dam Safety reported the failure of six dams as a result of this storm. Three of these dams are located upstream from USGS gaging stations. Saffrin Pond Dam, failed completely. It is located on Weldon Brook, a tributary to Lake Hopatcong, upstream from the USGS stage-only gage on Lake Hopatcong and the continuous-record streamflow-gaging station on Musconetcong River at the outlet of Lake Hopatcong. The New Jersey No Name # 89 Dam, located on a tributary to Crosswicks Creek in North Hanover Township in Burlington County upstream from the gage on Crosswicks Creek at Extonville, failed completely. The Bureau of Dam Safety also reported damage to the spillway at Cassville Dam, located on a small tributary to the Toms River, upstream from the gage on Toms River near Toms River. Water stored in these impoundments contributed to the flow past these gages during the flood. The portion of the hydrograph contributed by the dam breaches is not distinguishable from the runoff contributed by the rainfall.
The USGS New Jersey Water Science Center’s Hydrologic Data Assessment Program prepared for field work in response to the forecast of flood conditions the week before the high water occurred. Seven storm-surge sensors were deployed on Friday August 26 at tidal crest-stage gage sites along the coast in support of the USGS national storm-surge monitoring network. These sensors collected continuous water-level data throughout the storm to supplement the 24 long-term continuous-record tide gages along the back bays and tidal rivers along the coast.
Real-time data from USGS gaging stations across New Jersey were invaluable in planning the first line of response to the storm. The real-time data helped USGS personnel focus efforts on the watersheds experiencing the most flooding. Early Sunday morning, August 28, six crews were dispatched to selected gages to make discharge measurements. Two other crews collected water-quality samples on the rising limb of the hydrograph of the Delaware River at Trenton and Raritan River at Bound Brook gages for the USGS National Water Quality Assessment (NAWQA) Program. Sampling continued at these sites during the peak and recession on Monday and Tuesday, August 29–30. Samples were collected for bacteria analysis at six sites along the Passaic River on Wednesday, August 31, and Thursday, September 1.
Six crews continued to make high-water discharge measurements throughout the week. Over seventy-five discharge measurements were made from August 28 through September 2. Discharge measurements were the highest ever made at many long-term gages. Discharge measurements also were the highest ever made at many relatively new gages, defining the upper limb of the hydrograph. Discharge measurements were made at gages on small streams on August 28. Discharge measurements were made August 30–31 at or near the flood peak at gaging stations with drainage from large basins whose stream were slower to crest. Discharge measurements at some of these gages were made on the receding limb of the hydrograph during September 1–2. Photographs of the flooded areas were taken at many gaging stations.
Peak stage exceeded the upper end of the stage/discharge ratings at many gages. Discharge measurements were used to extend stage/discharge ratings at more than 25 stations. High-water marks were flagged for indirect measurements of peak flow at eight gaging stations.
The USGS New Jersey Water Science Center stayed in communication with the U.S. Army Corps of Engineers, New York District; the NWS Mount Holly forecast office; and the NWS Mid-Atlantic River Forecast office during the hurricane. Requests were answered for maximum recordable stages at flood-forecast gages, rating extensions at numerous gages, peak-stage and flow data from gages, comparisons of peaks from this storm with historic peaks, and the flood frequency of the event at various locations. The New Jersey Water Science Center participated in daily conference calls with the USGS National Flood Specialist and personnel at other Water Science Centers about flooding in east coast states. The Federal Emergency Management Agency (FEMA) was contacted by the New Jersey Water Science Center with an offer of assistance with flood-related work. A mission assignment was accepted to document high-water marks at more than 150 locations along streams that experienced record-breaking flooding.
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http://www.nola.com/hurricane/index.ssf/2011/08/hurricane_irene_makes_second_l.html.
National Weather Service, 2011a, National Weather Service—Advanced hydrologic prediction service, accessed August 30, 2011, at http://water.weather.gov/precip.
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New Jersey State Climatologist, 2011, Waterlogged NJ: August 2011 and Summer 2011 Summary, accessed September 12, 2011, at http://climate.rutgers.edu/stateclim/?section=menu&%20target=aug11.
Schopp, R.D., and Firda, G.D., 2008, Flood magnitude and frequency of the Delaware River in New Jersey, New York, and Pennsylvania: U.S. Geological Survey Open-file Report 2008–1203, 7 p. (Also available at http://pubs.usgs.gov/of/2008/1203/pdf/ofr2008-1203.pdf.)
U.S. Geological Survey, 2011, Summary of July 2011 monthly hydrologic conditions, accessed August 29, 2011, at http://nj.usgs.gov/special/monthly_summary/archive/2011/07/.
Watson, K.M., and Schopp, R.D., 2009, Methodology for estimation of flood magnitude and frequency for New Jersey streams: U.S. Geological Survey Scientific Investigations Report 2009-5167,51 p. (Also available at http://pubs.usgs.gov/sir/2009/5167/pdf/sir2009-5167.pdf.)