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Flooding in Maryland

On this page you learn what types of flooding are typical in Maryland and how do you protect yourself, your family and your home. You will also find out more about significant Maryland floods. Finally, you'll find links to NWS offices that provide forecast and safety information for Maryland as well as links to our partners who play a significant role in keeping you safe.

Flood Safety Home Page Turn Around Don't Drown Flood Safety Awareness Week Interactive Flood Map Types of flodding and associated risks NWS flood products forecasts and observations (AHPS) education and outreach partner agencies Flooding Navigation bar, hover for links Flood Safety Home Page Turn Around Don't Drown Interactive Flood Map Types of flodding and associated risks NWS flood products forecasts and observations (AHPS) flood safety education and outreach partner agencies National Water Center Whitemarsh Run in Whitemarsh, MD just below I-95 during Floyd. Photo by Maryland USGS Flood Safety Home Page Turn Around Don't Drown Flood Safety Awareness Week Interactive Flood Map Types of flodding and associated risks NWS flood products forecasts and observations (AHPS) education and outreach partner agencies
Significant Maryland Floods
  • Great Potomac and Susquehanna Flood of 1936, March 17-19

    Heavy snow fell throughout the winter of 1935-1936. Warmer temperatures and rainstorms in early March caused rivers to begin to rise. The primary flood-producing rains fell on March 17 and 18 when a storm dumped 1 to 6 inches of rain in 48 hours across much of the area. The Potomac River rose 10 feet above flood stage, setting record stages that still stand today at Paw Paw, Hancock, Williamsport, Harpers Ferry, Point of Rocks and Little Falls. The 1936 flood reached 17 feet above the C&O Canal towpath level, destroying lock houses and other operational aspects of the canal. Many businesses and homes in Point of Rocks were never rebuilt after the flood. Some 15 feet of water covered Main Street in Hancock, and the bridges crossing the Potomac in Hancock, Harpers Ferry and Shepherdstown were destroyed. Portions Cumberland were buried in mud and debris. Numerous fatalities were reported. This flood caused about $9.5 million in damage throughout the Potomac Basin. The U.S. Weather Bureau called it “the perfect storm” of its type. Similar severe flooding occurred on the Susquehanna, causing damage in Havre de Grace and Port Deposit. In the latter town, water was up to the second floor of homes, despite the recently-completed Conowingo Dam.

    President Franklin Delano Roosevelt toured the flood damage along the Potomac in March 1936, from The Washington Post, March 20, 1936.
    President Franklin Delano Roosevelt toured the flood damage along the Potomac in March 1936, from The Washington Post, March 20, 1936.

    High Water Mark in Williamsport, MD from the 1936 flood. Photo from the Herald-Mail, March 16, 2011.
    High Water Mark in Williamsport, MD from the 1936 flood. Photo from the
    Herald-Mail, March 16, 2011.

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  • Hurricane Agnes, June 22 -24, 1972

    Although Hurricane Agnes made landfall in the Florida Panhandle, the storm re-strengthened as it moved northward toward the Delmarva. Heavy rain had already occurred the week before Agnes, but nothing compared to what Agnes would bring. Nearly 15 inches of rain fell in Westminster (Carroll County), and Parkton (Baltimore County) recorded nearly a foot of rain in just 48 hours. Numerous smaller streams in the state set record high river levels that still stand today, including the Monocacy River, Patapsco River, NW Branch Anacostia River, and the Little Patuxent River. The Potomac at Little Falls crested more than 12 feet above flood stage, but well below the 1936 flood crest: $110 million in damages occurred in Maryland and DC combined.

    Rainfall totals compiled by WPC for the Agnes rainfall event
    Rainfall totals compiled by WPC for the Agnes rainfall event

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  • Twin Floods, January 19-20 and September 6-7, 1996

    Although these two floods were more than 7 months apart, they are being combined for one important reason: they affected much of the same area with almost the same impacts. In other words, two significant flood events happened in the same year in the same area, which is unusual. The January event was caused by a combination of warm air melting a snowpack combined with heavy rain. Wills Creek near Cumberland set a new flood of record, exceeding the 1936 flood by nearly three feet. The January 1996 flood was nearly a 100-year event (1 percent chance of occurrence in any given year). The September event, caused by the remnants of Hurricane Fran, produced significant rainfall, especially near the ridges. Although most of Maryland received little rain from the storm, the flow from the headwaters and Shenandoah River caused similar stream levels as those experienced in January, meaning two near-100-year, events occurred in the same year! The September flood caused significant damage along George’s Creek in Allegany County, including in the towns of Westernport and Lonaconing. The 1996 floods are the most recent major floods of the Potomac River; none has happened since to date.

    Tropical storm Fran rainfa,ll totals in Maryland

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  • Hurricane Floyd, September 16, 1999

    Hurricane Floyd made landfall in North Carolin then turned northeastward back out into the Atlantic Ocean. The storm, which was as strong as Category 4 before landfall, was still a Category 1 hurricane as it moved through the mid-Atlantic region. Chestertown, MD, recorded 12.59 inches of rain, and there were widespread reports of 2-4 feet of storm surge, with 5 to 7 foot storm surge in Somerset County. Unicorn Branch in Queen Anne's County, Morgan Creek in Kent County, and Little Elk Creek and Northeast Creek in Cecil County all reached or exceeded their calculated 500-year recurrence intervals. There were 5 injuries and $14.75 million in damages reported.

    Whitemarsh Run in Whitemarsh, MD just below I-95 during Floyd. Photo by Maryland USGS
    Whitemarsh Run in Whitemarsh, MD just below I-95 during Floyd. Photo by Maryland USGS

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  • Hurricane Isabel, September 18-19, 2003

    Hurricane Isabel made landfall on the outer banks of North Carolina on the 18th and moved into western Maryland by the 19th. An 8-foot storm surge was recorded on the Chesapeake Bay at Hoopers Island. Tolchester Beach set a record high tide of 7.91 feet above mean low water. Rainfall was not significant in this event for the state of Maryland, though much of the rain that fell in Virginia and West Virginia did drain into the Potomac and cause minor to moderate flooding. Storm surge, however, was a major factor; 6 foot waves battered the coastline of Saint Mary's County, destroying over 2,500 wharves and piers. The bridge to Saint George Island was destroyed along with 20 homes on the island. Some 6 feet of water filled the Annapolis Maritime Museum. Numerous buildings were damaged or destroyed along the Baltimore County shoreline and in Baltimore's Inner Harbor and Fells Point areas. The promenade boardwalk in Havre de Grace was destroyed.

    This flood marker, inside the National Aquarium at Baltimore’s Inner Harbor, is a reminder of the extreme flooding Isabel brought to the region.
    This flood marker, inside the National Aquarium at Baltimore's Inner Harbor, is a reminder of the extreme flooding Isabel brought to the region.


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Flood Hazard Information
  • Flash Flooding

    Flash flooding is a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (i.e., intense rainfall, dam failure, ice jam). More information...

  • River Flooding

    River flooding occurs when river levels rise and overflow their banks or the edges of their main channel and inundate areas that are normally dry. More information...
  • Tropical Systems and Coastal Flooding

    At any time of year, a storm from over the ocean can bring heavy precipitation to the U.S. coasts. Whether such a storm is tropical or not, prolonged periods of heavy precipitation can cause flooding in coastal areas, as well as further inland as the storm moves on shore. More information...

  • Ice/Debris Jams

    A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of ice or other debris. Debris Jam: A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of debris. More information...
  • Snowmelt

    Flooding due to snowmelt most often occurs in the spring when rapidly warming temperatures quickly melt the snow. The water runs off the already saturated ground into nearby streams and rivers, causing them to rapidly rise and, in some cases, overflow their banks.More information...
  • Dam Breaks/Levee Failure

    A break or failure can occur with little to no warning. Most often they are caused by water overtopping the structure, excessive seepage through the surrounding ground, or a structural failure. More information...
Protect Life and Property NWS Forecast Offices and River Forecast Centers (RFC) Covering Maryland