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New Hampshire has more than 16,000 miles of rivers and streams and the state's settlement pattern is confluent with these locations. Communities developed along the waterways that provided mills with power and transportation. As a result of this development pattern, the floodplains of the state were rapidly settled. The shift to industrialization during the mid-nineteenth century compounded the problem, residents moved to the floodplains of the cities and larger villages. Such encroachment leads to flooding problems, as the floodplains naturally extend the watercourses during significant storm events.

Since October of 2005, New Hampshire has experienced three presidential disaster declarations. These and prior events are captured in the table below.

 

 

New Hampshire’s Flood History

Date

Area Affected
(River Basins or Region)

Recurrence
Interval (yr)

Remarks

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, MA until 1902

March 24-30, 1826

Pemigewasset, Merrimack, Contoocook, Blackwater and Ashuelot

Unknown

 

April 21-24, 1852

Pemigewasset, 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, Souhegan, 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 the 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

Fourth flood recorded in the lower Merrimack River basin at Manchester, NH

June 15-16, 1943

Upper Connecticut, Diamond and Androscoggin

25 to >50

Intense rainfall exceeding 4 inches; highest stream stages of record in parts of the affected area

June, 1944

Merrimack River

Unknown

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 Ammonoosuc, 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

Piscataqua - Portsmouth

Unknown

Northeaster brought tides exceeding maximum 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 cover and the moderate to heavy rainfall. Third highest flood of record on the rivers

April, 1969

Merrimack River Basin

Unknown

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

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

February, 1978
(“The Blizzard of ‘78)

Coastal New Hampshire

Unknown

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

FEMA DR-71l-NH: Severe summer storms with heavy rains, tornadoes; flash flood and severe winds

March 31 - April 2, 1987

Androscoggin, Saco, Ossipee, Piscataquog, 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

FEMA DR-789-NH: Large rainfall event following the March 31- April 2 storm.

August 7-11, 1990

Statewide

Unknown

FEMA DR-876-NH: Series of storm events from August 7-11, 1990 with moderate to heavy rains during this period produced widespread flooding.

August 19, 1991

Statewide

Unknown

FEMA DR-917-NH: Hurricane Bob struck New Hampshire causing extensive damage in Rockingham and Strafford counties, but the effects were felt statewide.

October, 1996

Northern and Western Regions

Unknown

FEMA DR-1077-NH: Counties declared: Carroll, Cheshire, Coos, Grafton, Merrimack, and Sullivan.

October – November, 1995

Northern and Western Regions

Unknown

FEMA DR-1144-NH: Counties declared: Grafton, Hillsborough, Merrimack, Rockingham, Strafford, and Sullivan.

June — July, 1998

Central and Southern Regions

Unknown

FEMA DR-1231-NH: 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)

September 18- 19, 1999

Central and Southwest Regions

Unknown

FEMA DR-1305-NH: Heavy rains associated with Tropical Storm/Hurricane Floyd. Counties declared: 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.

August 11, 2008

Central and Southeastern Regions

Unknown

FEMA-1782-DR: Severe storms, tornado, and flooding, starting on July 24th.

September 5, 2008

Northern Region

Unknown

FEMA-1787-DR: Severe storms and flooding, between July 24th and August 14th.

October 3, 2008

Central and Southern Regions

Unknown

FEMA-1799-DR: Severe storms and flooding, starting on September 6th and 7th and continuing.

May 12, 2010

Rockingham County

10 to 25

FEMA-1913-DR: Severe storms and flooding, between March 14th and 31st.

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