St. Marys River at Great Mills, MD
River level and flood forecast · St. Marys County
The river is 5.3 ft below flood stage (7 ft).
Flow: 20 cubic feet per second (USGS).
The last 7 days and the forecast
NWS forecast issued Sun, Dec 31, 7 PM. Forecasts change as rain falls and as upstream water arrives.
Get flood alerts for this river
An email when the National Weather Service forecasts St. Marys River at Great Mills to flood, when it floods, and when it's over.
Flood stages
| Major flood stage | 10 ft |
| Moderate flood stage | 8 ft |
| Flood stage | 7 ft |
| Action stage | 5 ft |
| Record crest (August 20, 1969) | 13.34 ft |
What floods at each level
From the National Weather Service, highest first.
- 10 ftWidespread flooding is occurring in Great Mills with water approaching homes and businesses.
- 8 ftIndian Bridge Road begins to flood as flooding becomes more widespread in Great Mills.
- 7 ftFlat Iron Road begins to flood with water in some yards in Great Mills.
Highest crests on record
- 13.34 ft — August 20, 1969
- 12.98 ft — August 28, 2011
- 12.82 ft — September 16, 1999
- 12.08 ft — July 30, 1960
- 11.77 ft — August 13, 1955
Recent crests: 7.72 ft (January 10, 2024) · 9.16 ft (December 18, 2023) · 7.38 ft (May 1, 2023) · 6.04 ft (December 16, 2022) · 7.03 ft (July 26, 2022)
Up and down the river, and nearby
Not an official source. River levels, forecasts, flood stages and impacts are from the National Weather Service (GMRM2); flow from the U.S. Geological Survey. Readings are provisional. In a flood, follow your local officials and the NWS at weather.gov.