The October 2005 Flood in New Hampshire and the Westfield River in Massachusetts

The drainage area of the Connecticut River Basin is 11,250 square miles. Over a 10-day period in October, 2005, remnants of Tropical Storm “Tammy” and Subtropical Depression Twenty-Two merged with incoming continental cold fronts to produce torrential rains over interior New England. Particularly hard hit was the state of New Hampshire that saw roads and bridges wiped out, several reported deaths, and whole buildings destroyed. During this 10-day period, October 7-16, 2005, approximately 6-15 inches of rainfall occurred within the Connecticut River Basin.

The storm system was actually two rainfall events separated by about 1 week. The first event, influenced by remnants of Tammy, produced rainfall between 4” and 10” between October 7-10, with some 24-hr rainfall totals approaching 8”-9” at Surry Mountain and Otter Brook Dams in Keene, NH (100-year rainfall frequency is slightly over 6” in 24 hrs). The recorded peak discharge at the USGS in Hinsdale, NH was about 11,000 cfs. This is the highest recorded discharge since construction of Surry Mountain and Otter Brook and cursory analysis indicates that this event would have exceeded the historic September, 1938 flood at Hinsdale had Surry Mountain and Otter Brook not been constructed. The second rainfall event, influenced by moisture from remnants of Sub-tropical depression 22, produced between 3” and 8” from October 14-16. Rainfall totals during the entire 10-day period ranged from 10”-15” within the Connecticut River basin, which slightly exceeds 100-year frequency 10-day totals of 12”-13”.

This was considered a major flood event within some watersheds of New England and is estimated to be equal to or slightly greater than a 100-year flood event within the Keene, NH area downstream of our Surry Mountain and Otter Brook Dams. During these runoff events, flood control storage utilized at Corps reservoirs ranged from 30-96 percent within the Connecticut River basin. Surry Mountain Dam reached 96% full, peaking 1.5 ft. below spillway crest, and nearby Otter Brook Dam reached about 80% full.

The uncontrolled Cold River and its tributaries, located along the Connecticut River north of Hinsdale in the town of Alstead, NH also experienced extensive flooding. Other isolated pockets of high rainfall such as the headwaters of the West Branch Westfield near Huntington, MA (these areas are located in the Berkshire Mountains ) experienced record flooding. West Branch Westfield at Huntington Gage recorded about 31,000 cfs, which surpassed the previous flood of record of August, 1955 of about 26,000 cfs. Corps dams located in the Westfield watershed experienced rapid rises in their reservoirs but only utilized 41% storage at Knightville Dam and 35% storage at Littleville Dam.

Compact
The signatory states of Connecticut, Massachusetts, New Hampshire, and Vermont ratified this Compact (PDF printable file. Need Acrobat to read. Click here to download Acrobat for free).

Bylaws
Read or print the CRVFCC Bylaws adopted at the quarterly meeting of the Commission, held at Keene, New Hampshire, June 25, 1954. (PDF printable file. Need Acrobat to read. Click here to download Acrobat for free).