March 2010 floods in New London County, Conn., and Washington County, R.I.: Impacts and Implications NRE 2215 / project / Benson, Judy / April 19, 2011 1
On March 30 and 31, 2010, southeastern New England was hit by the worst flooding in decades. In New London County, the USGS declared it a 100-year flood, and in Washington County, USGS declared it a 200- to 500-year flood. 1 Rescue workers evacuate a family in Westerly, R.I. 2
More than $42 million in property damage Applications approved for individuals and households for FEMA assistance: New London County: 2,480 Washington County: 4,981 FEMA funds approved for individuals and households: New London County: $3.6 million Washington County: $7.7 million Number of residences impacted: New London County: 4,228 Washington County: 25,943 Number of businesses impacted: New London County: 279 Washington County: 718 Total impact estimate: New London County: $5.3 million Washington County: $37.1 million Population: New London County, Conn.: 266,830* Washington County, R.I.: 126,925* *2009 Estimate 3
USGS streamgage data from floods: Levels at five of 10 streamgages in the two counties reached record heights. Pawcatuck River at Westerly: Peak height during 2010 flood: 15.4 feet Previous peak for total record of gauge: 15 feet, 1938 Pawcatuck River at Wood River Junction: Peak height during 2010 flood: 11.16 feet Previous peak for total record of gauge: 7.8 feet, 1968 Wood River at Hope Valley: Peak height during 2010 flood: 13.7 feet Previous peak for total record of gauge: 10.3 feet, 1982 Wood River near Arcadia: Peak height during 2010 flood: 10.6 feet Previous peak for total record of gauge: 9 feet, 1982 Pendleton Hill Brook, North Stonington: Peak height during 2010 flood: 7.6 feet Previous peak for total record of gauge: 6.73 feet, 1982 4
Gage height and discharge hydrographs show rapid rise of floodwaters. 5
Evacuations, many roads impassible; bridges and dams damaged 6
Residents of Old Mystic try to stop floodwaters with sandbags. Below, an old mill building that housed a popular restaurant in the village center of North Stonington collapsed during the flood. 7
Blue Pond dam collapsed; 179 million gallons of water released, swamping roads and properties.2 Harold Ward, Brown U. professor emeritus of environmental studies, was among those whose properties were flooded by the dam. He estimated the dam break added three feet to the peak flood heights. Others affected by the dam break are considering a class-action lawsuit. Dam owner had been under state orders to make repairs. 8
A year later, signs of the damage remain: Two bridges in Washington County still closed. Bridge in North Stonington that is the main access to the town center awaits replacement. Some dams still awaiting repairs. A bridge on River Road in Old Mystic is badly undermined and has been reduced to a single lane since the floods. 9
Some businesses that were flooded have not fully recovered 3 10
and homeowners are still making repairs. Owners of a home on Chapman Pond in Westerly are replacing a deck and stairway that was destroyed by the flood. This is in a neighborhood that was isolated for a week because of impassible roads. 11
Total rainfall in Feb. and March 2010 was 25.4 inches in New London County and Washington County, more than half of the yearly total. 12
How much rain? 4 March 2010 precipitation: 16.34 inches (wettest March in 116-year record) Average monthly precipitation: 3.87 inches Average March precipitation: 4.43 inches Number of heavy rainstorms in March 16-30, 2010: 4 Total rainfall in February and March 2010: 25.4 inches Average annual precipitation total: 46.45 inches Figures for Washington County, R.I. All figures f 13
The Big Picture: 2010 was a year filled with natural disasters, such as the record heat wave and drought in Russia that destroyed 40 percent of the grain crop 14
and major flooding in 7 countries. The most severe flooding was in Pakistan. 15
Across the U.S., FEMA responded to 81 disasters in 2010, Flooding in Nashville, Tenn. the highest number since the start of the record in 1953. Average is 33 per year. La Nina weather pattern that year is cited as one factor in the number of disasters worldwide that year, but climate change is also a factor, scientists say. 16
In this part of the world 5 Annual precipitation across the Northeast has been increasing by about ¾ inch per year over the last 60 years. 73 percent of 219 weather stations showed increases in heavy rainstorms (4 inches or more in 48 hours); 92 percent also showed increases in moderate rainstorms (2-4 inches in 48 hours) 86 percent of stations showed increases in the amount of rainfall coming during the top one percent of precipitation events in a year in other words, the trend is for the heaviest rainfalls in a year to dump more rain than the heaviest storms of previous years. 17
Extreme rainfalls occurring more often 6 10-year events (4.5 inches or more in 24 hours): 74 percent increase 5-year events (3.9 inches or more): 76 percent increase 1-year events (2.6 inches or more): 85 percent increase Stations with data from 1900 show the rate of increase of extreme precipitation events has accelerated since 1948. 18
Rainfall increases and temperature Warming trend globally and regionally (1.5 to.33 degrees C per decade) Warmer air holds more water vapor, more rain. Pattern in keeping with climate change projections. 7 Data from New England streamgages in place an average of 75 years shows trend of more frequent and larger floods; pattern seen throughout Northern hemisphere. 8 Rivers in the sky are flooding the world with tropical waters. - RA Kerr, Nature vol. 313:435, 2006. 19
This was an extreme event, but it certainly fits into the patterns of climate change. It should serve as a warning that these types of events are much more likely to occur more frequently. It will probably happen again. - Prof. Thomas Boving, hydrologist in the College of the Environment and Life Sciences at the University of Rhode Island. He did an analysis of the flood and was himself affected by it. 20
What might this mean for the future? A streamgage on the Quinebaug River is surrounded by floodwaters, so USGS hydrologists needed a boat to check the instruments. High-water marking and data collection during and just after floods by the USGS and other agencies is more important than ever for planning decisions about wetlands preservation, bridge construction, culvert size, dam maintenance and intensity of development allowed in flood-prone areas. 9 21
Climate conditions are in flux, so old data can t be relied upon to project future patterns. We re dealing with a moving target. - Phil Zarriello, water surface specialist for the USGS office in Northborough, Mass., that collected data on the 2010 floods in R.I. and southeastern Massachusetts. Andrew Waite, USGS hydrologist, checks flow measurements at the streamgage on the Pawcatuck River at Wood River Junction, R.I. During the flood, he helped set high water marks throughout the area. At this spot, the waters rose as high as the top of the visible portion of the concrete gage house shown in this photo. 22
Requirements for how and where we build our homes, businesses, roads, wastewater treatment plants, power lines and other structures need to be re-evaluated. The problem with increasing frequency and intensity of extreme precipitation is that the 100-year flood is now occurring much more frequently Future increases in extreme precipitation are very likely. 10 23
Conclusions / Key Points The flood of 2010 was a significant, record-setting event in New London County, Conn., and Washington County, R.I. Damage was widespread. Levels of rainfall that preceded the flood set new records. Data from the flood is a valuable tool for future planning and riskreduction actions. The flood holds important lessons about the importance of dam maintenance, limiting development in flood-prone areas and emergency management. The experience of New London and Washington counties fits in with trends seen throughout New England, the Northeast and the world for increased flooding and flood intensity that are expected to continue. In this context, it appears very likely that these two counties will experience another flood of similar magnitude in the coming decades. 24
Footnotes 1 Zarriello, Phillip J. and Bent, Gardner C., U.S. Geological Survey, Elevation of the March-April 2010 Flood High Water in Selected River Reaches in Rhode Island, Open File Report 2011-1029. 2 Phone interview with David Chopy, chief of the Office of Compliance and Inspection, R.I. Dept. of Environmental Management. 3 Phone interview with Westerly Town Manager Steve Hartford 4 Boving, Thomas, The Great R.I. Flood of 2010: A Hydrological Assessment, PowerPoint presentation to the Wood-Pawcatuck Watershed Association, April 2011. 5, 6, 7 Wake, Cameron and Spierre, Susan, Trends in Extreme Precipitation Events for the Northeast United States, 1948-2007, University of New Hampshire, Carbon Solutions for New England, March 2010. 8 Kundzewicz, Zbigniew W.; Hirabayashi, Yukiko and Kanae, Shinjiro, River Floods in the Changing Climate Observations and Projections, Water Resources Manager, Dec. 2009, pgs. 2634 2646; Collins, Mathias J.; Evidence for Changing Flood Risk in New England Since the Late 20 th Century, Journal of the American Water Resources Association, April 2009, Vol. 45, No. 2, pgs. 279 290. 9 Phone interview with Phil Zarriello, USGS water surface specialist; and Collins, Mathias J.; Evidence for Changing Flood Risk in New England Since the Late 20 th Century, Journal of the American Water Resources Association, April 2009, Vol. 45, No. 2, pgs. 279 290. 10 Wake, Cameron and Spierre, Susan, Trends in Extreme Precipitation Events for the Northeast United States, 1948-2007, University of New Hampshire, Carbon Solutions for New England, March 2010. 25
Sources Zarriello, Phillip J. and Bent, Gardner C., U.S. Geological Survey, Elevation of the March-April 2010 Flood High Water in Selected River Reaches in Rhode Island, Open File Report 2011-1029 March 31, April 1 and April 2, 2010 editions of The Day, New London, Conn. Phone or in-person interviews with: William McGarry, town manager of Hopkinton, R.I.; Steve Hartford, town manager of Westerly, R.I.; David Choppy, chief of the Office of Compliance and Inspection for the Rhode Island Department of Environmental Management; Harold Ward, professor emeritus of environmental studies at Brown University; Christopher Fox, executive director of the Wood-Pawcatuck Watershed Association; Prof. Thomas Boving, hydrologist in the College of Environmental and Life Sciences at the University of Rhode Island; USGS hydrologists/water surface specialists Phillip Zarriello, Andrew Waite and Elizabeth Ahearn. Data from 10 USGS streamgages in New London County and Washington County: http://waterwatch.usgs.gov/new/?m=real&r=ct&w=map Federal Emergency Management Agency website, www.fema.gov; and phone interview with Dennis Pinkham, FEMA external affairs director, FEMA Region 1 Boving, Thomas, The Great R.I. Flood of 2010: A Hydrological Assessment, PowerPoint Presentation to the Wood-Pawcatuck Watershed Association, March 2010 Wake, Cameron and Spierre, Susan, Trends in Extreme Precipitation Events for the Northeast United States, 1948 2007, University of New Hampshire, Carbon Solutions New England, March 2010. Kundzewicz, Zbigniew W.; Hirabayashi, Yukiko and Kanae, Shinjiro, River Floods in the Changing Climate Observations and Projections, Water Resources Manager, Dec. 2009, pgs. 2634 2646. Collins, Mathias J.; Evidence for Changing Flood Risk in New England Since the Late 20 th Century, Journal of the American Water Resources Association, April 2009, Vol. 45, No. 2, pgs. 279 290. 26