January 2007 June 2006 Flood A summary of the flood and performance of the Basin Commission Susquehanna Flood Forecast and Warning System

Prior to June 2006, hydrologic conditions in the basin were dry, and the entire state of Pennsylvania was in

“Drought Watch” status. June brought Photo: D. Lupardo rapid change to the existing conditions as severe thunderstorms occurred during the first part of the month across the basin. On Friday, June 23, a weak The Susquehanna River Basin is one surface cold front moved through of the most flood prone watersheds in Pennsylvania scattering strong storms the nation and experiences flood-related and depositing as much as an inch of damages in excess of $150 million on Aerial photo of Lourdes Hospital, Broome County, NY. average every year. June 2006 will rain over parts of the basin, with most be remembered by some in the of the basin receiving one-quarter to Upper Susquehanna subbasin, moderate Susquehanna River Basin as producing one-half inch of rain. to major flooding occurred in the the worst flooding in recorded history. The weather pattern persisted Middle Susquehanna subbasin, and The most severe flooding in the basin through the end of June when a stalled minor to moderate flooding occurred occurred in the southern tier of front characterized by low pressure in the Lower Susquehanna subbasin. along the Susquehanna and Chenango centered over the Midwest and high The storm’s track spared the Chemung, Rivers and the eastern and central pressure centered off the Atlantic West Branch and Juniata subbasins, areas of Pennsylvania. Coast south of New Jersey affected resulting in only minor flooding. Low While a number of flood control projects contributions of flow from the western are in place to protect the citizens of the subbasins allowed the middle and lower basin, studies have determined the best mainstem Susquehanna River to way to further reduce flood damages accommodate excessive flows from the in the basin is through nonstructural Upper and Middle Susquehanna sub- measures such as flood forecast and basins without causing major flooding. warning systems. The Susquehanna Flood Forecast and Warning System (SFFWS) — The most severe flooding occurred coordinated by the Susquehanna River in New York along the Susquehanna Basin Commission since 1986 — provides and Chenango Rivers, devastating residents of the basin with warning and many communities including forecast information in advance of and Binghamton, Conklin, Greene, during flooding events. The program is June 23 cold front satellite photo. Oneonta, Owego, Sidney, Unadilla, a cooperative effort involving NOAA's the Northeast for about a week. The Union, Vestal, and Waverly. Preliminary National Weather Service, the U.S. opposing rotation of the two pressure results from the U.S. Geological Survey Geological Survey, U.S. Army Corps of systems channeled tropical moisture (USGS) indicate that discharges along Engineers, and the states of New York, directly over the Susquehanna River the Susquehanna River in New York Pennsylvania and Maryland. Basin. The National Weather Service were greater than the 100-year flood This report provides a summary of the (NWS) projected record flooding based and in some locations exceeded the June 2006 flood and SFFWS performance on this weather pattern and the rainfall 500-year flood — breaking long-standing during that flood for the purpose of it was expected to produce. records in several locations by as much developing and implementing Localized flash flooding began as 4 feet (see Table 1). In Pennsylvania, the recommendations that will improve June 25. The heaviest widespread gages at Tunkhannock, Bloomsburg, and the system for future flood events. rainfall occurred from June 26 to Hershey reached new record high levels. SUSQUEHANNA RIVER June 28, and by the time the storm The flood impacted 48 of 67 counties BASIN COMMISSION moved out of the basin on June 29, within the Susquehanna River Basin; 1721 North Front Street some areas had received 8 to 15 inches 11 in New York and 37 in Pennsylvania. Harrisburg, Pennsylvania 17102-2391 or more of rain (see Figure 1, next page). In each of these counties, a disaster 717.238.0423 • 717.238.2436 fax [email protected] • www.srbc.net As a result of widespread heavy declaration was made at either the state rainfall, record flooding occurred in the or federal level (see Figure 2, page 3), Figure 1. 2 making those counties eligible for disaster USGS GAGE RECORD CREST JUNE 06 relief funding. Some areas in the Maryland RIVER NAME (YEAR) CREST (ft) portion of the basin did receive heavy rainfall, but no significant flooding occurred. At the Chenango Sherburne, NY 11.20 (1914) 11.35 time of this report, estimated damages in Susquehanna Unadilla, NY 16.60 (1936) 17.73 New York and Pennsylvania are still being Susquehanna Bainbridge, NY 23.10 (1914) 27.03 compiled. Basinwide, thousands of homes Susquehanna Conklin, NY 20.83 (1948) 25.02 and businesses were severely impacted or Susquehanna Vestal, NY 30.50 (1936) 33.50 destroyed, hundreds of bridges were swept Susquehanna Waverly, NY 21.40 (1936) 22.52 away or left unstable, hundreds of miles of Tunkhannock Creek Tunkhannock, PA 19.97 (1996) 20.90 roadways were impacted, and hundreds Fishing Creek Bloomsburg, PA 15.18 (1972) 15.67 of millions of dollars in property damage Swatara Hershey, PA 15.36 (1975) 16.12 were incurred. Flood forecasts prompted Table 1. Record Flood Crests emergency response in many counties, including activation of evacuation plans, closures of flood levees, and installation of temporary berms and other flood damage reduction measures. In Pennsylvania, emergency managers reported that seven fatalities occurred in the Susque- hanna basin. Three fatalities occurred in the New York portion of the basin; one in Chenango County and two at the collapse of a culvert under Interstate 88 in Delaware County. Photo: C. Haupt

Washington Street Bridge, Binghamton, N.Y.

The flood impacted 48 of 67 counties within the Susquehanna River Basin.

“ Figure 2. ” 3 Susquehanna Flood Forec

The mission of the Susquehanna emergency management agencies Program Goals of the Flood Forecast and Warning System distribute the information to the Susquehanna Flood Forecast (SFFWS) is to provide timely and counties, and the counties then distribute and Warning System accurate forecasts and warnings to the information to local emergency reduce flood damages in the management officials and others who Develop a sustainable, state-of-the-art Susquehanna basin. need the forecasts. observational network Daily river stage forecast guidance • Develop a gridded observational is issued by the Middle Atlantic River The successful network Forecast Center (MARFC), which provides • Incorporate the use of radar-based specific estimates of flood crest stages 20-year effort behind streamflow velocity measurements at selected locations on rivers and Provide as much lead-time and accuracy major tributaries in the Susquehanna the SFFWS is a in forecasts and warning as practicably basin. The forecast stages are based possible on model results incorporating large model for interagency • Increase frequency of forecast amounts of hydrometeorological data updates including precipitation measured at a cooperation and • Evaluate the need for new number of gages, precipitation estimates forecast points from several weather radars, and partnership. Evaluate the spatial distribution of quantitative precipitation forecasts (QPF)“ flood damages in the basin prepared by support offices of the NWS. • Assess adequacy of existing The forecasts generated by MARFC The successful 20-year effort behind system for dealing with increased are disseminated to NWS offices in the SFFWS is a model for interagency urbanization and flooding in State College, Pa., Binghamton, N.Y., cooperation and partnership. The small watersheds and Mount Holly, N.J. Those offices in members of the Interagency Committee Expand the flood warning system to turn are responsible for issuing flood are committed to continued improvements support water resources management and flash flood watches and warnings to the Susquehanna program through of public water supply, drought, and in the basin. Watches indicate there is periodic evaluations of the system’s potential for flooding, and warnings performance. Through” development recreation within the basin • Develop long-term reservoir indicate flooding is imminent. of a strategic plan, the committee has inflow and basin outlet forecasts The NWS forecast offices disseminate identified methodologies and goals to • Adapt monitoring network for the information to state emergency ensure that the program continues to detection of water supply threats management agencies, other governmental meet the forecasting and warning needs bodies, and the news media. The state of the Susquehanna River Basin. Improve flood warning dissemination through the use of technology • Develop flood inundation maps Interagency Committee Members for prioritized areas Susquehanna River Basin Commission Increase public awareness, support, National Weather Service and utility of NWS products U.S. Geological Survey • Conduct education and outreach activities to promote loss reduction U.S. Army Corps of Engineers • Seek partnerships to leverage NY State Department of Environmental Conservation resources for warning and NY State Emergency Management Office dissemination Pennsylvania Department of Environmental Protection Develop a mechanism for administration Pennsylvania Emergency Management Agency and secure source of funding Pennsylvania Department of Community and Economic Development • Investigate options for ensuring adequate funding for anticipated Maryland Department of the Environment needs Maryland Emergency Management Agency

4 cast and Warning System

SFFWS Performance The initial forecast for the June 2006 flood event predicted a storm track that would have concentrated significantly more precipitation in the Susquehanna River Basin. The storm’s final track shifted 50 to 75 miles eastward and brought considerably less precipitation and runoff to the basin than initially anticipated. While the shift spared the Western and Lower portions of the basin from major flooding, it caused significant variability in predicted flood levels, particularly on the lower main stem Susquehanna River. Once the storm’s track was established, NWS issued accurate forecasts, and the overall performance of the SFFWS was good. Nevertheless, the Interagency Committee conducted an evaluation of all aspects of the SFFWS; the following discussion covers the performance of the SFFWS and any problems encountered during the 2006 flood.

Data Acquisition Heavy rainfall intensity in parts of New York caused river levels at some gages to rise to flood levels at a rate greater than the data transmittal window (4 hours) and forecast interval (6 hours). Nevertheless, overall feedback on forecast performance was positive for the region north of Wilkes-Barre. Radar rainfall algorithms failed to accurately estimate rainfall amounts, necessitating the incorporation of real-time rain gage and satellite data to improve accuracy of rainfall estimates. Overall, radar operation and transmission worked well. Record high flood elevations caused a number of problems at New York stream gages. River flows at both Conklin and Vestal exceeded the physical measurement capability of the gages, leaving forecasters Visit the SFFWS web site with no indication of how much water was flowing past those locations. Also, www.susquehannafloodforecasting.org several sites had water inside the gage house above the floor level, and 5 flood elevations at several gages exceeded The NWS convened a number of Aylesworth and Stillwater reservoirs the established rating curves. All gages conference calls during the June 2006 flood reached 70 to 75 percent of flood stor- in the Pennsylvania portion of the event with the intent of disseminating age capacity. basin remained functional during the weather and flood forecasts. Participants on The capacity of the levees in the storm and performed well. the calls included SFFWS partners and Vestal-Johnson City-Binghamton area USGS staff in New York made county emergency managers. The confer- was slightly exceeded and some minor 21 discharge measurements during the ence calls with county-based emergency overtopping occurred. The Pennsylvania event. The measurements are vital for managers were especially beneficial. developing and maintaining accurate USACE Baltimore District staff Estimated Damages Prevented relationships between water elevation expressed the need for better information by Federal Flood Damage (stage) at the gages and flows in the about downstream conditions to assist Reduction Projects river. However, USGS staff encountered decision making for releases from flood (provided by the Baltimore District problems obtaining information and damage reduction projects. of the U.S. Army Corps of Engineers) gaining access to closed roads and The NWS identified need for better • $130 million by the Binghamton bridges, which impacted their ability communication about releases from flood levee system in Broome County, N.Y. to obtain flow measurements. damage reduction projects for incorpo- • $230 million by the Endicott-Johnson ration into forecast models. City-Vestal levee system in Broome Forecasting Varying and fluctuating forecasts County, N.Y. On average, the forecast lead-time caused concern among some community • $460 million by the Wyoming Valley in the Susquehanna basin ranged from officials, particularly in Harrisburg, and levee system in Luzerne County, Pa. 7 to 17 hours, which met the 6-hour served to underscore the need to explain • $2 million by the Wyoming Valley goal of the SFFWS. Nevertheless, the uncertainties inherent in using the levee system in Lackawanna County, Pa. event posed challenges for the NWS in quantitative precipitation forecast (QPF). preparing forecasts. Forecast updates were occasionally • $45 million by East Sidney Lake in Delaware County, N.Y., along the Although the final storm track difficult to track due to problems with Upper Susquehanna River lessened flooding in the Lower Susquehanna the NWS web server. • by Whitney Point Lake basin, it caused severe flooding in the Discussions with community $35 million in Broome County, N.Y., along the Delaware and Mohawk River Basins. The emergency managers revealed that there Tioughnioga River simultaneous severe flooding in three may have been gaps in communications • $13 million by Stillwater Lake in river systems posed challenges for MARFC between release of NWS forecasts and Susquehanna County, Pa., along and Binghamton forecast office staff. their transmittal through the counties the Predicting rainfall locations with the to local entities. June 2006 flood was difficult due to the Department of Environmental Protection “mesoscale structure” of the storm and Flood Damage reported that seven small low-hazard the variability of precipitation amounts Reduction Projects dams failed in the Pennsylvania portion within that structure. As a result, rainfall No significant problems were reported of the Susquehanna basin. One high- predictions were overestimated in some at any of the USACE Baltimore District hazard dam (Big Elk dam in Susquehanna areas and underestimated in other areas. flood damage reduction projects. County) was overtopped and will require As river forecast modeling is highly Preliminary damage prevention repairs, but did not fail. dependent on rainfall input, some river estimates total $950 million in the forecasts failed to accurately capture Susquehanna basin ($850M prevented Emergency Response actual runoff and peak flow. Additionally, by levees and flood walls; $100M prevented •A temporary floodwall erected in intense rainfall caused rapid runoff that by dams). Scranton saved 1,800 homes could not be captured by the 6-hour Reductions in flood stage were from flooding. interval of MARFC forecast models, estimated at 2 to 2.5 feet on the Chenango • The Lackawanna Emergency and some flood crests occurred several and Upper Susquehanna Rivers, and 1 Management Office evacuated hours in advance of predictions. to 1.5 feet on the Chemung, Lackawanna, 250 people out of Old Forge, Pa. and mainstem Susquehanna below the •A forecast for flood levels at the top Dissemination and confluence with the . of Binghamton’s levee prompted an Communications The East Sidney and Aylesworth evacuation of 3,000 people from the city. NWS Eastern Region’s Advanced dams stored record volumes of water; •A precautionary decision was made Hydrologic Prediction Services (AHPS) use of the spillway at East Sidney for to order the evacuation of 200,000 web server experienced performance the first time in the 56-year history of people in the Wyoming Valley, and reliability problems due to excessive the project prompted erroneous reports including the City of Wilkes-Barre. user demand. of dam failure. The Whitney Point, Refined flood forecasts led to the 6 evacuation order being rescinded. Ultimately, about 60,000 people Recommendations for evacuated the area. • More than 1,200 people were successfully Improving the SFFWS rescued by emergency responders throughout Pennsylvania. • 300 people in the Town of Conklin Hydrologic Monitoring • Install and maintain real-time were airlifted. Forecast accuracy is limited by stream gages at the following sites: performance of data collection networks and o Middletown, Pa. (stage only) Community Outreach accuracy of QPF. By identifying gaps in (). Susquehanna River Basin Commission data coverage and addressing performance o Oneonta, N.Y. (SRBC) staff tracked forecasts and shortcomings, the quality and reliability of (Susquehanna River). hydrologic conditions leading up to hydrometeorological data can be improved, o Binghamton, N.Y. (stage only) and during the event, and shared thereby improving the accuracy and timeli- (Susquehanna River). information with the media, basin ness of forecasts. Based on the evaluation of •Establish and maintain rating curves legislators and community officials the SFFWS performance, recommendations at the following stage-only sites: as requested. SRBC staff handled are being made to improve existing gages, o Sherburne, Norwich and an unusually high volume of media provide gage coverage in areas that suffered Greene, N.Y. (). inquiries related to flooding effects on flooding but lack data, and generally o Oneonta, Unadilla, Bainbridge, water quality. The inquiries were largely enhance techniques used to collect and Windsor, Vestal and Owego, N.Y. in response to failure of a sewage treatment interpret hydrometeorological data. (Susquehanna River). plant in Oneonta, N.Y., and boil water The recommendations, to date, include: o Owego, N.Y. (Owego Creek). advisories in the Harrisburg area. •Raise the gagehouse floors and • Expand precipitation monitoring network SRBC staff and others encountered flood-proof the Rockdale, Unadilla, (telemetered gages with temperature significant problems trying to obtain Vestal and Conklin stream gages. sensors) to fill gaps in coverage at up-to-date information about NWS •Evaluate performance and implement or near the following locations: forecasts due to the aforementioned enhancements to reduce radar limi- o Vestal, Waverly, Oneonta, problems with the AHPS web site. tations in tracking observed rainfall. Cuyler/Homer area and As a follow up to the flood, SRBC • Extend the rating curves at all river Haskinville/Cohocton, N.Y., area. convened “Community Dialogue” forecast points to 125 percent above the •Reinstate functioning webcam at sessions in Binghamton, N.Y., and record flow, as time and funding allow. Conklin, N.Y.; evaluate expansion of Harrisburg, Pa., to garner local perspec- Priority locations identified to date: webcam network. tives on what worked well and what did Rockdale, Unadilla, Bainbridge, •Provide more site-specific monitoring not. These sessions gave participants Conklin, Cortland, Sherburne, Greene, and forecasting for smaller watersheds an opportunity to interact with flood Chenango Forks, Vestal, Owego, with shorter response time. management officials and to offer Waverly, and Chemung, N.Y.; and •Have agencies evaluate data manage- recommendations for improvements to Tunkhannock, Old Forge, ment problems associated with the SFFWS (see below for more information). and Bloomsburg, Pa. inadequate or too frequent data transmissions from gages. • Make available real-time information DIALOGUE SESSIONS WITH IMPACTED COMMUNITIES on road and bridge closures to On August 15 and 16, SRBC convened sessions in concern such as flood mapping and protection facilitate USGS operations and Binghamton, N.Y., and Harrisburg, Pa., respectively, of water quality against failure of wastewater measurements during flood events. to assess the performance of the SFFWS and treatment plants. the basin's flood damage reduction projects. Recommendations coming out of the two Forecast and Warning Products The sessions gave community officials and community dialogue sessions included: Generation others impacted by the flooding an opportunity • Designate a local contact in each municipality Gathering hydrometeorological to: (1) hear from agency officials responsible for to receive forecasts. data is the first step in flood forecasting. flood forecasting and emergency response; and • Evaluate implemention of a reverse 911 call system. Computer modeling, updating of forecasts (2) share their local perspectives on what • Undertake a basinwide “detention study” to and presentation of the forecast and worked well and what did not. assess efficacy of stormwater retention warning information are all vital to These sessions also gave participants an to reduce flood elevations. the generation of forecast and warning opportunity to offer comments and recommenda- • Secure funding for mitigation planning, products. Lessons learned during the tions for improvements to flood forecasting, flood as well as funding for pumps and hoses protection, communications, and other areas of for municipalities. June 2006 flood should allow improvements to the generation of these products if 7 Recommendations for Improving of flood inundation to provide the public to react to potential flood emergency managers a functional events. The following recommendations the SFFWS (continued) tool to facilitate emergency response. are designed to improve the value of the the following recommendations are • Increase public and agency understand- forecast by raising the general public’s implemented: ing of the QPF and its use in forecasts. understanding of the information they offer: •Evaluate modeling time steps and • Encourage NWS and local county •Improve understanding of NWS forecasting intervals and assess need partnership efforts to improve predicted flood characterization to provide more frequent updates communication, mitigation and (minor, moderate, major). of river stages and flood forecasts. response through participation in the •Emphasize that river forecasts •Develop modeled forecast points NWS “StormReady” community generally cover a range of 2 to 3 feet, at the following locations: program and county emergency and emphasize the inherent uncertainty o Oneonta, Windsor and planning and mitigation meetings. of forecasts using QPFs. Owego, N.Y. (Susquehanna River). Interagency Communications Water Quality •Develop crest-crest relationships for and Operations Water quality concerns associated forecasts at the following locations: The interaction between SFFWS with flooding are typically short term o Norwich, N.Y. partners is critical, particularly during in duration and mostly the result of (Chenango River). a flooding event. It is important that failed sewage treatment plants, oil o Binghamton, N.Y. information flow between partners is spills, and combined sewer overflows. (Susquehanna River). seamless. Challenges encountered The following recommendations could •Provide more forecast information on during the June 2006 flood present provide valuable data in the interest of the Lower Lackawanna River in the area an opportunity to improve the flow of public health and safety and assessing of the flood damage reduction project; information between agencies, through environmental impacts of flood events: evaluate reliability of local gages. the following recommendations: •Perform bacteriological monitoring •Provide forecast information on the •Establish direct and reliable at select locations during and after in the York, Pa., area; communication routes for flood events to assess water quality evaluate need for improvements to forecasts to the SFFWS partners. impacts to recreational uses. the gage, including relocation of • Continue the use of conference calls •Report nutrient and sediment load the gage off private property and with county emergency management data routinely gathered during each development and maintenance agencies (EMAs) and FEMA. individual flood event. of a rating curve. • Include PEMA, USGS, and SRBC • Modify graphical forecast products in the conference calls held between PROGRESS REPORT to display the range of probability NWS and the county EMAs. for river forecasts at each site, instead • Enhance communications with •USGS is currently working with the of one discrete forecasted stage. USACE regarding reservoir releases. Borough of Middletown, Pa., to complete •Refine and enhance techniques •Investigate the coordination of reservoir for monitoring and forecasting releases with MARFC; improve the initial installation for the new Swatara flash flooding. accessibility of release data to MARFC. Creek stage-only gage at Middletown. •Develop an internal emergency Full installation should be complete in Warning Dissemination action plan at SRBC to identify early 2007. The forecasts and warnings are only roles, responsibilities, and contacts as good as their distribution. The warnings for use during floods. •NWS has addressed AHPS performance need to reach the appropriate audiences through timely, reliable, and convenient Public Information and and reliability problems by increasing means. Successful dissemination of Education web server capacity. warnings requires clear communication A major component of successful of the forecast details and reliable flood forecasting and warning is proper •SRBC, in partnership with USGS and NWS, transmission of the forecast through understanding and application of the is developing flood inundation GIS layers. various media. Shortcomings encountered forecast information by the public. during the June 2006 flood can be Reactions to forecasts during the June 2006 •SRBC, in conjunction with SFFWS partners, addressed through the following flooding indicate that general understanding identified specific locations for precipitation recommendations: of the meaning, limitations, and applicability • Increase and enhance AHPS of forecasts can be improved. The better and stream gages in New York and is web server capacity. informed the audience is, the more useful currently finalizing installation logistics. •Develop GIS layers depicting areas and successful the products will be in aiding 8