New Hampshire has more than 16,000 miles of rivers and streams covering 9,282 square miles. Initially, communities developed along the waterways which provided transportation and mills with water power. Recently, New Hampshire has experienced significant flood events. During the 10-day period from October 7th through the 16th, 2005, approximately 6 to 15 inches of rainfall fell when remnants of Tropical Storm Tammy and Subtropical Depression Twenty-Two merged with incoming continental cold fronts to produce torrential rains over interior New England. This caused flooding in the Connecticut River and its tributaries, Ashelot River, Cold River and Otter Brook. New Hampshire was particularly hard hit with roads and bridges wiped out, several reported deaths, and several buildings destroyed. This was considered a major flood event especially for the Town of Alstead, which was hit the hardest, and other southwestern NH communities. A heavy rainfall of 8-12 inches fell on May 13-15, 2006 in the Merrimack and Piscataquoq River basins causing the worst flooding in the Concord and Manchester areas since September 1938. The USGS estimated that the storm was equal or slightly greater than a 100-year flood event. Floods of record were observed in the Warner, Piscataquog, Soucook, Lamprey, and Exeter Rivers.
December 1740 |
Merrimack |
Unknown |
First recorded flood in New Hampshire |
October 23, 1785 |
Cocheco, Baker, Pemigewasset, Contoocook and Merrimack |
Unknown |
Greatest discharge at Merrimack and at Lowell, Mass. Through 1902 |
March 24-30, 1826 |
Pemigewasset, Merrimack, Contoocook, Blackwater and Ashuelot |
Unknown |
|
April 2 1-24, 1852 |
Pernigewasset, Winnespaukee, Contoocook, Blackwater, and Ashuelot |
Unknown |
Merrimack River at Concord; highest stream stage for 70 years. Merrimack River at Nashua,; 2 feet lower than 1785 |
April 19-22, 1862 |
Contoocook, Merrimack, Piscataquog, and Connecticut |
Unknown |
Highest stream stages to date on the Connecticut River; due solely to snowmelt |
October 3-5, 1869 |
Androscoggin, Pemigewasset, Baker, Contoocook, Merrimack, Piscataquog Soughegan, Ammonoosuc, Mascoma, and Connecticut |
Unknown |
Tropical storm lasting 36 hours. Rainfall, 6-12 inches |
November 3-4, 1927 |
Pemigewasset, Baker, Merrimack, Ammonoosuc and Connecticut |
25 to>5O |
Upper Pemigewasset River and Baker River; exceeded the 1936 Flood. Down stream at Plymouth; less severe than 1936 flood |
March 11-21, 1936 |
Statewide |
25 to> 50 |
Double flood; first due to rains and snowmelt; second, due to large rainfall |
September 21,1938 |
Statewide |
Unknown |
Hurricane. Stream stages similar to those of March 1936 and exceeded 1936 stages in Upper Contoocook River |
June 1942 |
Merrimack River Basin |
Unknown |
This was the fourth flood in the lower Merrimack River basin at Manchester, NH |
June 15-16,1943 |
Upper Connecticut, Diamond and Androscoggin |
25 to >50 |
Intense rain exceeding 4 inches; highest stream stages of record in parts of the affected area |
June 1944 |
Merrimack River |
Unknown |
This was one of the five highest known floods at Manchester on the Merrimack |
November 1950 |
Contoocook River and Nubanusit Brook |
Unknown |
Localized storm resulted in flooding of this area |
March 27, 1953 |
Lower Androscoggin, Saco, Ossipee, Upper Amrnonoosuc Israel, and Ammonoosuc |
25 to>50 |
Peak of record for the Saco and Ossipee Rivers. |
August 1955 |
Connecticut River Basin |
Unknown |
Heavy rains caused extensive damage throughout the basin area |
October 25, 1959 |
White Mountain Area; Saco, Upper Pemigewasset and Ammonoosuc Rivers |
25 to>50 |
Largest of record on Ammonoosuc at Bethlehem Junctions; third largest of record on the Pemigewasset and Saco Rivers |
December 1959
|
Piscataquog - Portsmouth |
Unknown |
A Northeaster brought tides exceeding maxim tidal flood levels in Portsmouth. Damage was heavy along the coast |
April 1960 |
Merrimack and Piscataquog |
Unknown |
Flooding resulted from rapid melting of deep snow covering and the moderate to heavy rainfall. This was the third highest flood of record on the rivers |
April 1969 |
Merrimack River Basin |
Unknown |
A record depth of snow cover in the Merrimack River Basin and elsewhere resulted in excessive snowmelt and runoff when combined with sporadic rainfall |
February 1972 |
Coastal Area |
Unknown |
The Coastal Area was declared a National Disaster Area as a result of the devastating effects of a severe coastal storm, damage was extensive |
June 1972 |
Pemigewasset River
- |
Unknown |
Five days of heavy rain caused some of the worst flooding since 1927 along streams in the upper part of the State, damage was extensive along the Pemigewasset River and smaller streams in northern areas |
June 30, 1973 |
Ammonoosuc River |
25 to >50 |
Northwestern White Mountains |
April 1976 |
Connecticut River |
Unknown |
Rain and snowmelt brought the river to 1972 levels, flooding roads and croplands. |
March 14,1977 |
South-central and Coastal New Hampshire |
25 to 50 |
Peak of record for Soucook River |
Februaiy 1978
(“The Blizzard of ‘78) |
Coastal New Hampshire |
Unknown |
A Nor’easter brought strong winds and precipitation to the entire state. Hardest hit area was the coastline, with wave action and floodwaters destroying homes. Roads all along the coast were breached by waves flooding over to meet the rising tidal waters in the marshes |
July 1986-August 10,1986 |
Statewide |
Unknown |
Severe summer storms with heavy rains, tornadoes; flash flood and severe winds
FEMA DR-71l-NH |
March31 to April 2, 1987 |
Androscoggin, Saco, Ossipee, Pi5c2:taquOg, Pemigewasset, Merrimack & Contoocook River |
25 to >50 |
Caused by snowmelt and Sense rain Precursor to a significant, following event |
April 6-7, 1987 |
Lamprey River and Beaver Brook |
25 to>50 |
Large rainfall quantities following the March 31- April 2 storm. FEMA DR-789-NH |
August 7-11, 1990 |
Statewide |
Unknown |
A series of storm events from August 7-11, 1990 with moderate to heavy rains during this period produced widespread flooding. FEMA DR-876-NH |
August 19, 1991 |
Statewide |
Unknown |
Hurricane Bob struck New Hampshire causing extensive damage in Rockingham and Stafford counties, but the effects were felt statewide.
FEMA DR-917-NH |
October 1996 |
Northern and Western Regions |
Unknown |
Counties Declared Carroll, Cheshire, Coos, Grafton, Merrimack, and Sullivan. FEMA DR-1077-NH |
October – November 1995 |
Northern and Western Regions |
Unknown |
Counties Declared:Grafton, Hillsborough, Merrimack, Rockingham, Strafford & Sullivan.
FEMA DR-1144-NH |
June — July 1998 |
Central and Southern Regions |
Unknown |
Series of rainfall events. Counties Declared: Belknap, Grafton, Carroll, Merrimack, Rockingham and Sullivan. (1fatality) (Several weeks earlier, significant flooding, due to rain and rapid snowpack melting, occurred in Coos County, undeclared in this event. Heavy damage to secondary roads occurred) FEMA DR-1231-NH |
September 18- 19, 1999 |
Central and Southwest Regions |
Unknown |
FEMA DR-1305-NH: Heavy rains associated with Tropical Storm/Hurricane Floyd. Counties Designated: Belknap, Cheshire and Grafton. |
July 21 - August 18, 2003 |
Southwestern Region |
Unknown |
FEMA-1489-DR: Severe Storms and Flooding occurred in Cheshire and Sullivan counties. Public Assistance provided for repair of disaster damaged facilities. |
October 7 -16, 2005 |
Southwestern Region |
Exceeded 100 in some areas |
FEMA-1610-DR: Heavy rains associated with Tropical Storm Tammy and Subtropical Depression 22 resulted in 6-15 inches of rain. |
May 13-15, 2006 |
Central and Southern NH |
Exceeded 100 |
FEMA-1643-DR: Heavy Rainfall 8-16 inches |
April 27, 2007 |
Statewide |
100 |
FEMA – 1695-DR – Severe storms and flooding, starting on April 15th. |
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