Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW)
Maryland — Water Level & Flood Stage
Located in Baltimore City County, Maryland on the Northwest Branch Patapsco River. Live water level data from USGS, updated every 15 minutes.
Current Water Level
Gage Height
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Streamflow
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Last Reading
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This is an NWS forecast point (LID: BLTM2). Live data may be limited. View on NWS AHPS →
Flood Stages
Major Flood
6 ft
Moderate Flood
4.6 ft
Minor Flood
3.4 ft
Action Stage
2.5 ft
Flood stages defined by the National Weather Service. Gage height data from USGS Water Resources.
What Floods at Each Level
6.5 ft
Water approaches Caroline Street.
6 ft
Water reaches the corner of Ann Street and Thames Street.
5.5 ft
Water begins to cover the Pier 4 promenade on the west side and Pier 5 on the west side.
5.25 ft
The boardwalk at Fells Point begins to flood. Water also begins to cover low spots in the promenade at the end of Broadway Street.
5 ft
Water begins to cover the Pier 4 promenade on the east side.
4.5 ft
The end of Ann Street begins to flood.
4.25 ft
The concrete promenade at Fells Point begins to flood. Water also begins to cover the boardwalk at the Maritime Park water taxi stop.
3.5 ft
Water begins to cover the promenade at the Inner Harbor at the electric boat dock west of the World Trade Center. A half foot of water covers parts of Thames Street in the Fells Point area.
3 ft
Flooding is occurring at the end of Thames Street. Water also nearly covers the promenade at the dragon boat dock in the Inner Harbor.
2 ft
Water begins to cover the lower promenade at the Harbor Place water taxi stop.
Impact statements from the National Weather Service, describing what typically happens at each water level.
7-Day Water Level Chart
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Historic Crests
| Date | Stage | Flow |
|---|---|---|
| Aug 13, 2025 | 9.77 ft | — |
| Aug 13, 2025 | 9.77 ft | — |
| Sep 19, 2003 | 8.15 ft | — |
| Sep 19, 2003 | 8.15 ft | — |
| Aug 22, 1933 | 7.69 ft | — |
About This Gauge
NWS LID
BLTM2
River
Northwest Branch Patapsco River
County
Baltimore City, MD
Coordinates
39.2700°N, 76.5800°W
Get Flood Alerts for Northwest Branch Patapsco River
StormCast monitors this gauge and sends a push notification to your phone when the water level crosses into a new flood category — even at 3 AM.
Frequently Asked Questions
What is the current water level of Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW)?
The Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW) gauge is maintained by USGS and reports water levels every 15 minutes. Visit this page to see the latest reading updated live, or download StormCast to get push alerts when levels rise.
What is flood stage for Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW)?
The NWS-defined flood stage for Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW) is 3.4 feet. Action stage begins at 2.5 feet. Moderate flooding starts at 4.6 feet, and major flooding at 6 feet.
How do I get alerts when Northwest Branch Patapsco River rises?
Download StormCast free on Google Play, go to River Gauges, and add Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW) to your watchlist. StormCast will send a push notification to your phone whenever the water level crosses into a new NWS flood category — even when your screen is off.
Where is the Northwest Branch Patapsco River at Baltimore/Fort McHenry (IN MLLW) gauge located?
The gauge is located in Baltimore City County, Maryland at coordinates 39.2700°N, 76.5800°W. Data is provided by the U.S. Geological Survey and the National Weather Service.
More Resources
Source & Notes
Data provided by: National Ocean Service
- <head> <meta charset="utf-8"> <style type="text/css"> .style1 { background-color: #FFFF00; } </style> </head> Please refer to <a href="https://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=CFW&format=CI&version=1&glossary=1"><font color="#0000ff"><span class="style1">Coastal Flood Advisories and Warnings</span></font></a> for official water level forecasts during periods of coastal flooding. During tropical cyclones, please refer<span class="style1"> </span> <span class="style1"> <a href="https://forecast.weather.gov/product.php?site=NWS&issuedby=lwx&product=TCV&format=CI&version=1&glossary=1">here</a></span> for additional storm surge information.
- Stage may be affected by ice.