Prior to June 2006, hydrologicconditions in the basin were dry, andthe entire state of Pennsylvania was in“Drought Watch” status. June broughtrapid change to the existing conditionsas severe thunderstorms occurred duringthe first part of the month across thebasin. On Friday, June 23, a weaksurface cold front moved throughPennsylvania scattering strong stormsand depositing as much as an inch ofrain over parts of the basin, with mostof the basin receiving one-quarter toone-half inch of rain.

The weather pattern persistedthrough the end of June when a stalledfront characterized by low pressurecentered over the Midwest and highpressure centered off the AtlanticCoast south of New Jersey affected

the Northeast for about a week. Theopposing rotation of the two pressuresystems channeled tropical moisturedirectly over the Susquehanna RiverBasin. The National Weather Service(NWS) projected record flooding basedon this weather pattern and the rainfallit was expected to produce.

Localized flash flooding beganJune 25. The heaviest widespreadrainfall occurred from June 26 toJune 28, and by the time the stormmoved out of the basin on June 29,some areas had received 8 to 15 inchesor more of rain (see Figure 1, next page).

As a result of widespread heavyrainfall, record flooding occurred in the

Upper Susquehanna subbasin, moderateto major flooding occurred in theMiddle Susquehanna subbasin, andminor to moderate flooding occurredin the Lower Susquehanna subbasin.The storm’s track spared the Chemung,West Branch and Juniata subbasins,resulting in only minor flooding. Lowcontributions of flow from the westernsubbasins allowed the middle and lowermainstem Susquehanna River toaccommodate excessive flows from theUpper and Middle Susquehanna sub-basins without causing major flooding.

The most severe flooding occurredin New York along the Susquehannaand Chenango Rivers, devastatingmany communities includingBinghamton, Conklin, Greene,Oneonta, Owego, Sidney, Unadilla,Union, Vestal, and Waverly. Preliminaryresults from the U.S. Geological Survey(USGS) indicate that discharges alongthe Susquehanna River in New Yorkwere greater than the 100-year floodand in some locations exceeded the500-year flood — breaking long-standingrecords in several locations by as muchas 4 feet (see Table 1). In Pennsylvania, thegages at Tunkhannock, Bloomsburg, andHershey reached new record high levels.

The flood impacted 48 of 67 countieswithin the Susquehanna River Basin;11 in New York and 37 in Pennsylvania.In each of these counties, a disasterdeclaration was made at either the stateor federal level (see Figure 2, page 3),

The Susquehanna River Basin is one of the most flood prone watersheds in

the nation and experiences flood-relateddamages in excess of $150 million on

average every year. June 2006 will be remembered by some in the

Susquehanna River Basin as producing the worst flooding in recorded history. The most severe flooding in the basin

occurred in the southern tier of New Yorkalong the Susquehanna and Chenango

Rivers and the eastern and central areas of Pennsylvania.

While a number of flood control projectsare in place to protect the citizens of thebasin, studies have determined the best

way to further reduce flood damages in the basin is through nonstructural measures such as flood forecast and

warning systems. The Susquehanna FloodForecast and Warning System (SFFWS) —

coordinated by the Susquehanna RiverBasin Commission since 1986 — provides

residents of the basin with warning and forecast information in advance of and

during flooding events. The program is a cooperative effort involving NOAA's

National Weather Service, the U.S.Geological Survey, U.S. Army Corps ofEngineers, and the states of New York,

Pennsylvania and Maryland.

This report provides a summary of theJune 2006 flood and SFFWS performance

during that flood for the purpose of developing and implementing

recommendations that will improve the system for future flood events.

Susquehanna RiverBasin Commission

June 2006 FloodA summary of the flood and performance of the

Susquehanna Flood Forecast and Warning System

Aerial photo of Lourdes Hospital, Broome County, NY.

June 23 cold front satellite photo.

S U S Q U E H A N N A R I V E R B A S I N C O M M I S S I O N

1 7 2 1 N o r t h F r o n t S t r e e tH a r r i s b u r g , P e n n s y l v a n i a 1 7 1 0 2 - 2 3 9 1

7 1 7. 2 3 8 . 0 4 2 3 • 7 1 7. 2 3 8 . 24 3 6 f a xs r b c @ s r b c . n e t • w w w. s r b c . n e t

Pho

to: D

. Lup

ardo

January 2007

Figure 1.2

USGS GAGE RECORD CREST JUNE 06RIVER NAME (YEAR) CREST (f t)

Chenango Sherburne, NY 11.20 (1914) 11.35Susquehanna Unadilla, NY 16.60 (1936) 17.73Susquehanna Bainbridge, NY 23.10 (1914) 27.03Susquehanna Conklin, NY 20.83 (1948) 25.02Susquehanna Vestal, NY 30.50 (1936) 33.50Susquehanna Waverly, NY 21.40 (1936) 22.52Tunkhannock Creek Tunkhannock, PA 19.97 (1996) 20.90Fishing Creek Bloomsburg, PA 15.18 (1972) 15.67Swatara Hershey, PA 15.36 (1975) 16.12

Figure 2.

making those counties eligible for disasterrelief funding. Some areas in the Marylandportion of the basin did receive heavy rainfall,but no significant flooding occurred. At thetime of this report, estimated damages inNew York and Pennsylvania are still beingcompiled. Basinwide, thousands of homesand businesses were severely impacted ordestroyed, hundreds of bridges were sweptaway or left unstable, hundreds of miles ofroadways were impacted, and hundreds of millions of dollars in property damagewere incurred.

Flood forecasts promptedemergency response in manycounties, including activationof evacuation plans, closures offlood levees, and installation of temporary berms and other flooddamage reduction measures.

In Pennsylvania, emergencymanagers reported that sevenfatalities occurred in the Susque-hanna basin. Three fatalitiesoccurred in the New York portionof the basin; one in ChenangoCounty and two at the collapseof a culvert under Interstate 88 in Delaware County.

Table 1. Record Flood Crests

Pho

to: C

. Hau

pt

“”The flood

impacted 48 of 67counties within

the SusquehannaRiver Basin.

Washington Street Bridge, Binghamton, N.Y.

3

Susquehanna Flood ForecThe mission of the Susquehanna

Flood Forecast and Warning System(SFFWS) is to provide timely andaccurate forecasts and warnings toreduce flood damages in theSusquehanna basin.

Daily river stage forecast guidanceis issued by the Middle Atlantic RiverForecast Center (MARFC), which providesspecific estimates of flood crest stagesat selected locations on rivers andmajor tributaries in the Susquehannabasin. The forecast stages are basedon model results incorporating largeamounts of hydrometeorological dataincluding precipitation measured at anumber of gages, precipitation estimatesfrom several weather radars, andquantitative precipitation forecasts (QPF)prepared by support offices of the NWS.

The forecasts generated by MARFCare disseminated to NWS offices inState College, Pa., Binghamton, N.Y.,and Mount Holly, N.J. Those offices inturn are responsible for issuing floodand flash flood watches and warningsin the basin. Watches indicate there ispotential for flooding, and warningsindicate flooding is imminent.

The NWS forecast offices disseminatethe information to state emergencymanagement agencies, other governmentalbodies, and the news media. The state

emergency management agenciesdistribute the information to thecounties, and the counties then distributethe information to local emergencymanagement officials and others whoneed the forecasts.

The successful 20-year effort behindthe SFFWS is a model for interagencycooperation and partnership. Themembers of the Interagency Committeeare committed to continued improvementsto the Susquehanna program throughperiodic evaluations of the system’sperformance. Through developmentof a strategic plan, the committee hasidentified methodologies and goals toensure that the program continues tomeet the forecasting and warning needsof the Susquehanna River Basin.

Program Goals of theSusquehanna Flood Forecast

and Warning SystemDevelop a sustainable, state-of-the-artobservational network

• Develop a gridded observational network

• Incorporate the use of radar-basedstreamflow velocity measurements

Provide as much lead-time and accuracyin forecasts and warning as practicablypossible

• Increase frequency of forecast updates

• Evaluate the need for new forecast points

Evaluate the spatial distribution of flood damages in the basin

• Assess adequacy of existing system for dealing with increased urbanization and flooding in small watersheds

Expand the flood warning system tosupport water resources managementof public water supply, drought, andrecreation within the basin

• Develop long-term reservoir inflow and basin outlet forecasts

• Adapt monitoring network for detection of water supply threats

Improve flood warning disseminationthrough the use of technology

• Develop flood inundation maps for prioritized areas

Increase public awareness, support,and utility of NWS products

• Conduct education and outreach activities to promote loss reduction

• Seek partnerships to leverage resources for warning and dissemination

Develop a mechanism for administrationand secure source of funding

• Investigate options for ensuring adequate funding for anticipated needs

4

Interagency Committee MembersSusquehanna River Basin Commission

National Weather Service U.S. Geological Survey

U.S. Army Corps of Engineers NY State Department of Environmental Conservation

NY State Emergency Management Office Pennsylvania Department of Environmental Protection

Pennsylvania Emergency Management Agency Pennsylvania Department of Community and Economic Development

Maryland Department of the Environment Maryland Emergency Management Agency

“”

The successful 20-year effort behind

the SFFWS is amodel for interagency

cooperation andpartnership.

cast and Warning System

The initial forecast for the June 2006flood event predicted a storm track thatwould have concentrated significantlymore precipitation in the SusquehannaRiver Basin. The storm’s final trackshifted 50 to 75 miles eastward andbrought considerably less precipitationand runoff to the basin than initiallyanticipated. While the shift spared theWestern and Lower portions of the basinfrom major flooding, it caused significantvariability in predicted flood levels,particularly on the lower main stemSusquehanna River. Once the storm’strack was established, NWS issued accurateforecasts, and the overall performanceof the SFFWS was good. Nevertheless,the Interagency Committee conducted anevaluation of all aspects of the SFFWS; thefollowing discussion covers the performanceof the SFFWS and any problemsencountered during the 2006 flood.

Data AcquisitionHeavy rainfall intensity in parts of

New York caused river levels at somegages to rise to flood levels at a rategreater than the data transmittal window(4 hours) and forecast interval (6 hours).Nevertheless, overall feedback on forecastperformance was positive for the regionnorth of Wilkes-Barre.

Radar rainfall algorithms failed toaccurately estimate rainfall amounts,necessitating the incorporation ofreal-time rain gage and satellite data toimprove accuracy of rainfall estimates.Overall, radar operation and transmissionworked well.

Record high flood elevations caused anumber of problems at New York streamgages. River flows at both Conklin andVestal exceeded the physical measurementcapability of the gages, leaving forecasterswith no indication of how much waterwas flowing past those locations. Also,several sites had water inside the gagehouse above the floor level, and

5

V i s i t t h e S F F WS we b s i t ewww.susquehannafloodforecasting.org

SFFWS Performance

flood elevations at several gages exceededthe established rating curves. All gagesin the Pennsylvania portion of thebasin remained functional during thestorm and performed well.

USGS staff in New York made21 discharge measurements during theevent. The measurements are vital fordeveloping and maintaining accuraterelationships between water elevation(stage) at the gages and flows in theriver. However, USGS staff encounteredproblems obtaining information andgaining access to closed roads andbridges, which impacted their abilityto obtain flow measurements.

ForecastingOn average, the forecast lead-time

in the Susquehanna basin ranged from7 to 17 hours, which met the 6-hourgoal of the SFFWS. Nevertheless, theevent posed challenges for the NWS inpreparing forecasts.

Although the final storm track lessened flooding in the Lower Susquehannabasin, it caused severe flooding in theDelaware and Mohawk River Basins. Thesimultaneous severe flooding in threeriver systems posed challenges for MARFCand Binghamton forecast office staff.

Predicting rainfall locations with theJune 2006 flood was difficult due to the“mesoscale structure” of the storm andthe variability of precipitation amountswithin that structure. As a result, rainfallpredictions were overestimated in someareas and underestimated in other areas.As river forecast modeling is highlydependent on rainfall input, some riverforecasts failed to accurately captureactual runoff and peak flow. Additionally,intense rainfall caused rapid runoff thatcould not be captured by the 6-hourinterval of MARFC forecast models,and some flood crests occurred severalhours in advance of predictions.

Dissemination andCommunications

NWS Eastern Region’s AdvancedHydrologic Prediction Services (AHPS)web server experienced performanceand reliability problems due to excessiveuser demand.

The NWS convened a number ofconference calls during the June 2006 floodevent with the intent of disseminatingweather and flood forecasts. Participants onthe calls included SFFWS partners andcounty emergency managers. The confer-ence calls with county-based emergencymanagers were especially beneficial.

USACE Baltimore District staffexpressed the need for better informationabout downstream conditions to assistdecision making for releases from flooddamage reduction projects.

The NWS identified need for bettercommunication about releases from flooddamage reduction projects for incorpo-ration into forecast models.

Varying and fluctuating forecastscaused concern among some communityofficials, particularly in Harrisburg, andserved to underscore the need to explainuncertainties inherent in using thequantitative precipitation forecast (QPF).Forecast updates were occasionallydifficult to track due to problems withthe NWS web server.

Discussions with communityemergency managers revealed that theremay have been gaps in communicationsbetween release of NWS forecasts andtheir transmittal through the countiesto local entities.

Flood Damage Reduction Projects

No significant problems were reportedat any of the USACE Baltimore Districtflood damage reduction projects.Preliminary damage preventionestimates total $950 million in theSusquehanna basin ($850M preventedby levees and flood walls; $100M preventedby dams).

Reductions in flood stage wereestimated at 2 to 2.5 feet on the Chenangoand Upper Susquehanna Rivers, and 1to 1.5 feet on the Chemung, Lackawanna,and mainstem Susquehanna below theconfluence with the Chemung River.

The East Sidney and Aylesworthdams stored record volumes of water;use of the spillway at East Sidney forthe first time in the 56-year history ofthe project prompted erroneous reportsof dam failure. The Whitney Point,

Aylesworth and Stillwater reservoirsreached 70 to 75 percent of flood stor-age capacity.

The capacity of the levees in theVestal-Johnson City-Binghamton areawas slightly exceeded and some minorovertopping occurred. The Pennsylvania

Department of Environmental Protectionreported that seven small low-hazarddams failed in the Pennsylvania portionof the Susquehanna basin. One high-hazard dam (Big Elk dam in SusquehannaCounty) was overtopped and will requirerepairs, but did not fail.

Emergency Response• A temporary floodwall erected in

Scranton saved 1,800 homes from flooding.

• The Lackawanna EmergencyManagement Office evacuated250 people out of Old Forge, Pa.

• A forecast for flood levels at the topof Binghamton’s levee prompted anevacuation of 3,000 people from the city.

• A precautionary decision was madeto order the evacuation of 200,000people in the Wyoming Valley,including the City of Wilkes-Barre.Refined flood forecasts led to the

6

Estimated Damages Prevented

by Federal Flood Damage

Reduction Projects

(provided by the Baltimore District

of the U.S. Army Corps of Engineers)

• $130 million by the Binghamton levee system in Broome County, N.Y.

• $230 million by the Endicott-JohnsonCity-Vestal levee system in BroomeCounty, N.Y.

• $460 million by the Wyoming Valleylevee system in Luzerne County, Pa.

• $2 million by the Wyoming Valley levee system in Lackawanna County, Pa.

• $45 million by East Sidney Lake inDelaware County, N.Y., along the Upper Susquehanna River

• $35 million by Whitney Point Lake in Broome County, N.Y., along theTioughnioga River

• $13 million by Stillwater Lake inSusquehanna County, Pa., along the Lackawanna River

evacuation order being rescinded.Ultimately, about 60,000 peopleevacuated the area.

• More than 1,200 people were successfullyrescued by emergency respondersthroughout Pennsylvania.

• 300 people in the Town of Conklinwere airlifted.

Community OutreachSusquehanna River Basin Commission

(SRBC) staff tracked forecasts andhydrologic conditions leading up toand during the event, and sharedinformation with the media, basinlegislators and community officialsas requested. SRBC staff handledan unusually high volume of mediainquiries related to flooding effects onwater quality. The inquiries were largelyin response to failure of a sewage treatmentplant in Oneonta, N.Y., and boil wateradvisories in the Harrisburg area.

SRBC staff and others encounteredsignificant problems trying to obtainup-to-date information about NWSforecasts due to the aforementionedproblems with the AHPS web site.

As a follow up to the flood, SRBCconvened “Community Dialogue”sessions in Binghamton, N.Y., andHarrisburg, Pa., to garner local perspec-tives on what worked well and what didnot. These sessions gave participantsan opportunity to interact with floodmanagement officials and to offerrecommendations for improvements tothe SFFWS (see below for more information).

Hydrologic MonitoringForecast accuracy is limited by

performance of data collection networks andaccuracy of QPF. By identifying gaps indata coverage and addressing performanceshortcomings, the quality and reliability ofhydrometeorological data can be improved,thereby improving the accuracy and timeli-ness of forecasts. Based on the evaluation ofthe SFFWS performance, recommendationsare being made to improve existing gages,provide gage coverage in areas that sufferedflooding but lack data, and generallyenhance techniques used to collect andinterpret hydrometeorological data.The recommendations, to date, include:• Raise the gagehouse floors and

flood-proof the Rockdale, Unadilla,Vestal and Conklin stream gages.

• Evaluate performance and implementenhancements to reduce radar limi-tations in tracking observed rainfall.

• Extend the rating curves at all riverforecast points to 125 percent above therecord flow, as time and funding allow.Priority locations identified to date:Rockdale, Unadilla, Bainbridge,Conklin, Cortland, Sherburne, Greene,Chenango Forks, Vestal, Owego,Waverly, and Chemung, N.Y.; andTunkhannock, Old Forge, and Bloomsburg, Pa.

• Install and maintain real-timestream gages at the following sites:

o Middletown, Pa. (stage only) (Swatara Creek).

o Oneonta, N.Y. (Susquehanna River).

o Binghamton, N.Y. (stage only) (Susquehanna River).

• Establish and maintain rating curvesat the following stage-only sites:

o Sherburne, Norwich and Greene, N.Y. (Chenango River).

o Oneonta, Unadilla, Bainbridge, Windsor, Vestal and Owego, N.Y. (Susquehanna River).

o Owego, N.Y. (Owego Creek).• Expand precipitation monitoring network

(telemetered gages with temperaturesensors) to fill gaps in coverage at or near the following locations:

o Vestal, Waverly, Oneonta, Cuyler/Homer area and Haskinville/Cohocton, N.Y., area.

• Reinstate functioning webcam atConklin, N.Y.; evaluate expansion of webcam network.

• Provide more site-specific monitoringand forecasting for smaller watershedswith shorter response time.

• Have agencies evaluate data manage-ment problems associated withinadequate or too frequent datatransmissions from gages.

• Make available real-time informationon road and bridge closures tofacilitate USGS operations andmeasurements during flood events.

Forecast and Warning ProductsGeneration

Gathering hydrometeorologicaldata is the first step in flood forecasting.Computer modeling, updating of forecastsand presentation of the forecast andwarning information are all vital tothe generation of forecast and warningproducts. Lessons learned during theJune 2006 flood should allow improvementsto the generation of these products if

On August 15 and 16, SRBC convened sessions inBinghamton, N.Y., and Harrisburg, Pa., respectively,to assess the performance of the SFFWS andthe basin's flood damage reduction projects.The sessions gave community officials andothers impacted by the flooding an opportunityto: (1) hear from agency officials responsible forflood forecasting and emergency response; and(2) share their local perspectives on whatworked well and what did not.

These sessions also gave participants anopportunity to offer comments and recommenda-tions for improvements to flood forecasting, floodprotection, communications, and other areas of

concern such as flood mapping and protection of water quality against failure of wastewatertreatment plants.

Recommendations coming out of the two community dialogue sessions included:• Designate a local contact in each municipality

to receive forecasts.• Evaluate implemention of a reverse 911 call system.• Undertake a basinwide “detention study” to

assess efficacy of stormwater retention to reduce flood elevations.

• Secure funding for mitigation planning, as well as funding for pumps and hoses for municipalities.

7

Recommendations for Improving the SFFWS

DIALOGUE SESSIONS WITH IMPACTED COMMUNITIES

Recommendations for Improving the SFFWS (continued)

the following recommendations areimplemented:• Evaluate modeling time steps and

forecasting intervals and assess needto provide more frequent updates of river stages and flood forecasts.

• Develop modeled forecast points at the following locations:

o Oneonta, Windsor andOwego, N.Y. (Susquehanna River).

• Develop crest-crest relationships forforecasts at the following locations:

o Norwich, N.Y. (Chenango River).

o Binghamton, N.Y. (Susquehanna River).

• Provide more forecast information onthe Lower Lackawanna River in the areaof the flood damage reduction project;evaluate reliability of local gages.

• Provide forecast information on theCodorus Creek in the York, Pa., area;evaluate need for improvements tothe gage, including relocation of the gage off private property anddevelopment and maintenance of a rating curve.

• Modify graphical forecast productsto display the range of probabilityfor river forecasts at each site, insteadof one discrete forecasted stage.

• Refine and enhance techniques for monitoring and forecasting flash flooding.

Warning DisseminationThe forecasts and warnings are only

as good as their distribution. The warningsneed to reach the appropriate audiencesthrough timely, reliable, and convenientmeans. Successful dissemination ofwarnings requires clear communicationof the forecast details and reliabletransmission of the forecast throughvarious media. Shortcomings encounteredduring the June 2006 flood can beaddressed through the followingrecommendations:• Increase and enhance AHPS

web server capacity.• Develop GIS layers depicting areas

of flood inundation to provide emergency managers a functionaltool to facilitate emergency response.

• Increase public and agency understand-ing of the QPF and its use in forecasts.

• Encourage NWS and local countypartnership efforts to improvecommunication, mitigation andresponse through participation in theNWS “StormReady” communityprogram and county emergencyplanning and mitigation meetings.

Interagency Communicationsand Operations

The interaction between SFFWSpartners is critical, particularly duringa flooding event. It is important thatinformation flow between partners isseamless. Challenges encounteredduring the June 2006 flood presentan opportunity to improve the flow ofinformation between agencies, throughthe following recommendations:• Establish direct and reliable

communication routes for forecasts to the SFFWS partners.

• Continue the use of conference callswith county emergency managementagencies (EMAs) and FEMA.

• Include PEMA, USGS, and SRBCin the conference calls held between NWS and the county EMAs.

• Enhance communications withUSACE regarding reservoir releases.

• Investigate the coordination of reservoirreleases with MARFC; improve theaccessibility of release data to MARFC.

• Develop an internal emergencyaction plan at SRBC to identifyroles, responsibilities, and contactsfor use during floods.

Public Information andEducation

A major component of successfulflood forecasting and warning is properunderstanding and application of theforecast information by the public.Reactions to forecasts during the June 2006flooding indicate that general understandingof the meaning, limitations, and applicabilityof forecasts can be improved. The betterinformed the audience is, the more usefuland successful the products will be in aiding

the public to react to potential floodevents. The following recommendationsare designed to improve the value of theforecast by raising the general public’sunderstanding of the information they offer:• Improve understanding of NWS

predicted flood characterization(minor, moderate, major).

• Emphasize that river forecasts generally cover a range of 2 to 3 feet,and emphasize the inherent uncertaintyof forecasts using QPFs.

Water QualityWater quality concerns associated

with flooding are typically short termin duration and mostly the result offailed sewage treatment plants, oilspills, and combined sewer overflows.The following recommendations couldprovide valuable data in the interest ofpublic health and safety and assessingenvironmental impacts of flood events:• Perform bacteriological monitoring

at select locations during and afterflood events to assess water qualityimpacts to recreational uses.

• Report nutrient and sediment loaddata routinely gathered during eachindividual flood event.

PROGRESS REPORT

• USGS is currently working with the

Borough of Middletown, Pa., to complete

initial installation for the new Swatara

Creek stage-only gage at Middletown.

Full installation should be complete in

early 2007.

• NWS has addressed AHPS performance

and reliability problems by increasing

web server capacity.

• SRBC, in partnership with USGS and NWS,

is developing flood inundation GIS layers.

• SRBC, in conjunction with SFFWS partners,

identified specific locations for precipitation

and stream gages in New York and is

currently finalizing installation logistics.

8