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Floods of 2010: Examining Observed and Future Impacts of Increased Rainfall and Flooding

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1. The Floods of March 2010Examining Observed and Future Impacts of Increased Rainfall and Flooding<br />David R. ValleeHydrologist-in-ChargeNWS/Northeast River…
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  • 1. The Floods of March 2010Examining Observed and Future Impacts of Increased Rainfall and Flooding<br />David R. ValleeHydrologist-in-ChargeNWS/Northeast River Forecast Centerhttp://weather.gov/nerfc<br />Providence Street – West Warwick, RI at 1030 am Wednesday 3/31/10<br />
  • 2. The NOAA Hurricane Outlook for the Atlantic Basin!<br />But first: A Public Service Announcement!<br />Hurricane Bob – Landfall 8/19/1991<br />Bonnet Shores after Carol - 8/31/1954<br />
  • 3. What is forecast for the 2011 Season?<br />ACE Index Estimate<br />Conditions Setup <br />Named Storms: 12-18Hurricanes: 6-10Major Hurricanes: 3-6 (Cat 3, 4 or 5) <br />
  • 4. Active Season = Greater Threat?<br />Consider the following regarding hurricanes which <br /> made landfall on the coast of southern New England:<br />1938 Season storm total = 8 (Cat 3)<br /> 1944 Season storm total = 11 (Cat 3)<br /> Carol/Edna ‘54 Season storm total = 10 (2 Cat 3’s)<br /> Donna/1960 Season storm total = 7 (Cat 2)<br /> Gloria 1985 Season storm total = 11 (Cat 2)<br /> Bob 1991 Season storm total = 8 (Cat 2)<br />
  • 5. The theme of the prevailing summer weather pattern ultimately determines our vulnerability<br />Point at which New Englanders needs to take action!<br />
  • 6. The Floods of March 2010Examining Observed and Future Impacts of Increased Rainfall and Flooding<br />Outline<br />* A bit about the Northeast River Forecast Center<br />* What ingredients brought us to such a remarkable flood event in March 2010?<br />* Historical Perspective<br />* What does this all mean in light of climate change? <br />Providence Street – West Warwick, RI at 1030 am Wednesday 3/31/10<br />
  • 7. River Forecast Center Responsibilities<br />Calibrate and implement a variety of hydrologic and hydraulic models to provide:<br />River flow and stage forecasts at 180 locations<br />Guidance on the rainfall needed to produce Flash Flooding<br />Ensemble streamflow predictions<br />Ice Jam and Dam Break support <br />Water Supply forecasts<br />Partner with NOAA Line Offices to address issues relating to Hazard Resiliency, Water Resource Services, Ecosystem Health and Management, and Climate Change<br />Moderate flooding - Connecticut River at Portland, CT.<br />
  • 8. http://www.weather.gov/nerfc<br />Click on “Self Brief Page”<br />NERFC Hydromet Self-briefing Page<br />
  • 9. So what brought us to the tipping point during the last week of March 2010?<br />It was not caused by<br />One single Nor’easter or one Coastal Storm<br />Snowmelt<br />Improper water management<br />
  • 10. So what brought us to the tipping point?<br />It was caused by:<br />The atmospheric river – “energized” by El Nino<br />Blocking high pressure over Greenland<br />A sequence of heavy rainfall events over 5 weeks<br />Record monthly rainfall totaling 12-18 inches<br />Axis of each event over Pawcatuck & Pawtuxet Valleys<br />Saturated ground<br />A “chuck-full” Scituate Reservoir <br />Designed for Water Supply not Flood Control!<br />Swollen streams and ponds running well above normal<br />The lack of nature’s grasses, flowers and trees<br />Pre-growing season – no Evapo-transpiration to help us out<br />
  • 11. Major to Record flooding across southeast New England<br />
  • 12. The Blackstone ResponseDodged a huge bullet – as heaviest rains stayed south of the basin Considerable flooding on mainstem and many small streams<br />
  • 13. The Pawtuxet’s Record Response<br />Dramatic “urban response” in the lower basin followed by record reservoir flows from Scituate Reservoir<br />
  • 14. Pawcatuck Basin – similar responses<br />Pawcatuck River – Wood River Junction<br />Pawcatuck River – Westerly, RI<br />
  • 15. Historical Footnotes<br />Extremely rare to set two record flood elevations in two weeks – as was done on the Pawtuxet<br />Consider this fact:<br />The storms in March 2010 dumped over 16 inches of rain<br />The record Flood for the Blackstone in 1955 was the result of over 10 inches in ONE DAY with over 14 to 16 inches of rain in 1 week in Woonsocket northward through the head waters in Worcester.<br />Fits pattern of more intense heavy rainfall events which have been impacting the Northeast since the mid 1990s.<br />Merrimack Oct’96, Hurricane Floyd flooding Sept ‘99, Connecticut, Merrimack, Blackstone Oct’05, Mother’s Day 2006 Merrimack valley, May 2007, and now March 2010<br />An accumulation of “change” <br />
  • 16. The Basin itself…many twists/turns and tremendous urbanization of the lower watershed post 1968 – which corresponds to the jump in flood frequencies<br />Natic Dam<br />Royal Mill Dam<br />Arctic Dam<br />
  • 17. Pawtuxet River Flood Frequency<br />Post Mall and I-95 construction<br />
  • 18. Blackstone River Flood History<br />Post USACE Flood Control Product Construction<br />
  • 19. Rhode Island Temperature Trend<br />Annual TemperatureProvidence, RI 1933-2010<br />*<br />Trend line: y=1/61x +18.65<br />*<br />Prediction for 2020= 51.8F<br />Courtesy of Ryan ValleeClass of 2015 NCMS<br />
  • 20. Rhode Island Precipitation Trend<br />Annual PrecipitationProvidence, RI 1933-2010<br />*<br />*<br />Courtesy of Ryan ValleeClass of 2015 NCMS<br />
  • 21. Rhode Island Snowfall Trend<br />Seasonal SnowfallProvidence, RI 1933-2010<br />*<br />*<br />Courtesy of Ryan ValleeClass of 2015 NCMS<br />
  • 22. Climate Change Scenarios:Shorter snow season – less days with snow on the groundMore precipitation falling as rain prior to spring “green-up”<br />Burakowski et al., 2008, JGR<br />
  • 23. Climate Change Scenarios:Increase in 1 inch and 2 inch rainfall events<br />1 inch events (1947-2007)<br />2 inch events (1947-2007)<br />Spierre et al., 2008<br />Spierre et al., 2008<br />
  • 24. There has been a shift in Return Frequency<br />Most significant in the 25 to 100 yr recurrence interval.<br />
  • 25. Implications:<br />Impacts on the floodplain, land use, infrastructure, dam spillway requirements, drainage requirements, non-point source runoff, bridge clearances, “hardening” of critical facilities in the floodplain, property values etc…<br />Flood Insurance – work to increase participation<br />How much risk are we willing to insure and accept?<br />Graphic courtesy of Cameron Wake<br />University of New Hampshire<br />
  • 26. The Floods of March 2010Examining Observed and Future Impacts of Increased Rainfall and Flooding<br />David R. ValleeHydrologist-in-ChargeNWS/Northeast River Forecast Centerhttp://weather.gov/nerfc<br />Providence Street – West Warwick, RI at 1030 am Wednesday 3/31/10<br />
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    Aug 19, 2017
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