Web Portal Changes: The Advanced Hydrologic Prediction Service (AHPS) hosted at https://water.weather.gov will be replaced by the National Water Prediction Service (NWPS), with a target of March 2024. Existing AHPS content and features will be preserved and expanded within NWPS.

Experimental National Water Center Products: The National Hydrologic Discussion, Area Hydrologic Discussion, and Flood Hazard Outlook, and real-time geospatial services depicting River Forecast Center and National Water Model forecasts, continue to be accessible via https://www.weather.gov/owp/operations, as described in the StoryMap here.

Weather Forecast Office Philadelphia/Mount Holly, NJ

Middle Atlantic River Forecast Center

Coastal Flood Advisory

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: Graphical forecasts are not available for the Rehoboth Bay at Dewey Beach (IN MLLW). During times of high water, forecast crest information can be found in the text products. 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: 5.3 Moderate Flood Stage: 4.3 Flood Stage: 3.3 Action Stage: 0 Low Stage (in feet): -2 Historic Crests (1) 7.34 ft on 03/06/1962 (2) 5.73 ft on 10/29/2021 (3) 5.68 ft on 10/29/2012 (4) 5.04 ft on 10/11/2019 (5) 4.99 ft on 10/03/2022 Show More Historic Crests (P): Preliminary values subject to further review. Recent Crests (1) 4.49 ft on 12/23/2022 (2) 4.74 ft on 12/16/2022 (3) 4.99 ft on 10/03/2022 (4) 4.59 ft on 05/08/2022 (5) 5.73 ft on 10/29/2021 Show More Recent Crests (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

If you notice any errors in the below information, please contact our Webmaster
7.34	(Mean Lower Low Water (MLLW)) The level reached on March 6, 1962.
5.73	(MLLW) The level reached on October 29, 2021.
5.68	(MLLW) The level reached on October 29, 2012 during Post Tropical Cyclone Sandy.
5.3	(MLLW) MAJOR FLOODING. At this level, flooding starts to become severe enough to begin causing structural damage along with widespread flooding of roadways near Rehoboth Bay and the tidal waterways that flow into it. 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.
4.3	(MLLW) MODERATE FLOODING. At this level, widespread flooding of roadways begins with many roads becoming impassable near Rehoboth Bay and the tidal waterways that flow into it. Lives may be at risk when people put themselves in harm's way. Some damage to vulnerable structures may begin to occur. COASTAL FLOOD WARNING LEVEL.
3.6	(MLLW) COASTAL FLOOD ADVISORY LEVEL.
3.5	(MLLW) Flooding begins at Old Landing on Rehoboth Bay. Flooding begins along sections of DE Route 1 between Dewey Beach and Indian River Inlet, including the Delaware Seashore State Park. Flooding begins in Dewey Beach.
3.3	(MLLW) MINOR FLOODING.

About This Location

Latitude: 38.690200° N, Longitude: 75.078500° W, Horizontal Datum: NAD83/WGS84 River Stage Reference Frame Gauge Height Flood Stage Uses NWS stage 0 ft 3.3 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 -1.12 2.18 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 -0.53 1.65 NAVD88 to MHHW conversion from NOAA Vertical Datum Transformation (VDatum) Current/Historical Observations: U.S. Geological Survey (USGS) Data and Site Info for Dewey Beach (IN MLLW)

Additional Information

All gage data is referenced in MLLW. 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

Collaborative Agencies The National Weather Service prepares its forecasts and other services in collaboration with agencies like the US Geological Survey, US Bureau of Reclamation, US Army Corps of Engineers, Natural Resource Conservation Service, National Park Service, ALERT Users Group, Bureau of Indian Affairs, and many state and local emergency managers across the country. For details, please click here. NWS Information National Weather Service Philadelphia/Mount Holly Weather Forecast Office 732 Woodlane Road Mount Holly, NJ 08060-9615 (609) 261-6600 Ask Questions/Webmaster Page last modified: 2-Nov-2020 7:30 PM Disclaimer Credits Glossary Privacy Policy About Us Career Opportunities