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Weather Forecast Office Philadelphia/Mount Holly, NJ

Middle Atlantic River Forecast Center

Hydrograph

River at a Glance

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NOTE: Please refer to our Coastal Hazard Message for specific information regarding Coastal Flood Watches, Warnings and Advisories.  During tropical cyclones, please refer here for additional storm surge information. NOTE: Flood impacts are based on long-term averages. Actual impacts from any tidal flooding event may vary due to factors such as rainfall, wave action, and the number of tide cycles during which there is an onshore flow. NOTE: Forecasts are not available for the Sluice Creek at S. Dennis (IN MLLW). Only observed stages are available for this point. Vertical Datum references a tidal datum (MLLW)...for more information see Tides and Currents .

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Flood Categories (in feet) Major Flood Stage: 9.1 Moderate Flood Stage: 8.1 Flood Stage: 7.1 Action Stage: 0 Low Stage (in feet): -2 Historic Crests (1) 10.08 ft on 09/27/1985 (2) 9.49 ft on 10/30/2012 (3) 7.16 ft on 12/17/2020 (P): Preliminary values subject to further review. Recent Crests (1) 7.16 ft on 12/17/2020 (2) 9.49 ft on 10/30/2012 (3) 10.08 ft on 09/27/1985 (P): Preliminary values subject to further review. Low Water Records Currently none available.

Zoom Level:16 Legend FEMA Layer Gauge Location Disclaimer Latitude/Longitude Disclaimer: The gauge location shown in the above map is the approximate location based on the latitude/longitude coordinates provided to the NWS by the gauge owner.

Flood Impacts & Photos

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10.08	(Mean Lower Low Water (MLLW)) The level reached on September 27, 1985 during Hurricane Gloria.
9.49	(MLLW) The level reached on October 30, 2012 during Post Tropical Cyclone Sandy.
9.1	(MLLW) MAJOR FLOODING. At this level, flooding starts to become severe enough to begin causing structural damage along with widespread flooding of roadways near the bay in Dennis Township and Middle Township. Vulnerable homes and businesses may be severely damaged as water levels rise further above this threshold. Numerous roads become impassable and some neighborhoods may be isolated. The flood waters become a danger to anyone who attempts to cross on foot or in a vehicle.
8.1	(MLLW) MODERATE FLOODING. At this level, widespread flooding of roadways begins with many roads becoming impassable near the bay in Dennis Township and Middle Township. Lives may be at risk when people put themselves in harm's way. Some damage to vulnerable structures may being to occur. COASTAL FLOOD WARNING LEVEL.
7.4	(MLLW) COASTAL FLOOD ADVISORY LEVEL.
7.3	(MLLW) Flooding occurs along the Delaware Bay shoreline in Dennis Township and Middle Township.
7.1	(MLLW) MINOR FLOODING.

About This Location

Latitude: 39.161700° N, Longitude: 74.832200° W, Horizontal Datum: NAD83/WGS84 River Stage Reference Frame Gauge Height Flood Stage Uses NWS stage 0 ft 7.1 ft Interpreting hydrographs and NWS watch, warnings, and forecasts, and inundation maps Vertical Datum Elevation (gauge height = 0) Elevation (gauge height = flood stage) Elevation information source NAVD88 -3.48 3.62 Survey grade GPS equipment, FEMA flood plain maps, newer USGS topographic maps NGVD 29 Not Available Not Available Older USGS topographic maps, NGVD29 benchmarks MSL Not Available Not Available Older USGS topographic maps, MSL benchmarks Other -2.88 0.74 NAVD88 to MHHW conversion from NOAA Vertical Datum Transformation (VDatum) Current/Historical Observations: U.S. Geological Survey (USGS) Data and Site Info for S. Dennis (IN MLLW)

Additional Information

All gage data has been converted to MLLW following the National Ocean Service protocal. Gage data displayed on the USGS website is in NAVD88. During winter months, cold and ice may result in inaccurate real-time stages. Adjustments or deletions of this data can only be done after detailed analysis.

Resources

Hydrologic Resources Text Products Past Precipitation Forecast Precipitation River Forecast Centers River Stage Summary Inundation Mapping Locations

Additional Resources Area Hydrographs NWS Precipitation and River Forecasting AHPS Iframes for Developers Mobile iNWS for emergency management Snow Information Ensemble River Forecasts Hourly Precipitation

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