Major Flood
35 ft
Current Water Level
Gage Height
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Streamflow
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Last Reading
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FLOOD STAGES
Know the flood categories.
Flood stages defined by the National Weather Service. Gage height data from USGS Water Resources.
Moderate Flood
26 ft
Minor Flood
18 ft
Action Stage
16 ft
What Floods at Each Level
40 ft
This is a disastrous...life threatening flood. This compares to the Great New England Flood of 1936. Follow the advice of local officials...and evacuate if told to do so.
35 ft
This is a major...life threatening flood event. The river has not reached this height since the Great New England flood of 1936. Major flooding will affect the communities of Merrimack and Litchfield through Nashua and Hudson. follow the advice of local officials...evacuate if told to do so. Stay away from the Merrimack River.
30 ft
This flood compares to the Hurricane of 1938 flood. This is a substantial flood event. Follow the directions of local officials...evacuate if told to do so. At this height the Merrimack River is moving very swiftly. Stay away from the river.
28 ft
The river has not reached this height since the Hurricane of 1938. This is a serious flood event. Follow the advice of local officials...evacuate if told to do so. At this height...the Merrimack River is moving very swiftly. Stay away from the river.
25 ft
The river has not reached this height since May 2006. This is a significant flood event. Follow the advice of local officials...evacuate if told to do so.
21 ft
Flooding will occur in low lying areas from Litchfield and Merrimack...to Hudson and Nashua.
18 ft
Flooding will begin in the lower lying sections of Hudson and Nashua as the river continues to climb above 18 feet.
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 |
|---|---|---|
| Mar 19, 1936 | 41.3 ft | — |
| Sep 22, 1938 | 30.5 ft | — |
| May 15, 2006 | 26 ft | — |
About This Gauge
USGS Site
NWS LID
NSHN3
River
Merrimack River
County
Hillsborough, NH
Coordinates
42.7634°N, 71.4428°W
Get Flood Alerts for Merrimack 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 Merrimack River at Nashua?
The Merrimack River at Nashua gauge is maintained by USGS (site 01096508) 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 Merrimack River at Nashua?
The NWS-defined flood stage for Merrimack River at Nashua is 18 feet. Action stage begins at 16 feet. Moderate flooding starts at 26 feet, and major flooding at 35 feet.
How do I get alerts when Merrimack River rises?
Download StormCast free on Google Play, go to River Gauges, and add Merrimack River at Nashua to your watchlist. StormCast will send a push notification to your phone whenever the water level crosses into a new NWS flood category.
Where is the Merrimack River at Nashua gauge located?
The gauge is located in Hillsborough County, New Hampshire at coordinates 42.7634°N, 71.4428°W. USGS site number: 01096508. Data is provided by the U.S. Geological Survey and the National Weather Service.
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Source & Notes
Data provided by: US Geological Survey, Observations courtesy of U.S. Geological Survey