flood warning and forecasting issues in the srwmd

Flood Warning and Forecasting Flood Warning and Forecasting Issues in the SRWMDIssues in the SRWMD

Suwannee Suwannee River BasinRiver Basin

Georgia

Florida

240 Miles Long, 9,950 Square Miles

Headwaters

Okefenokee Swamp: Suwannee River

Cordele, GA: Alapaha River

Tifton, GA: Withlacoochee River

State Line at River Mile 207Only 43% of Basin is in Florida

Suwannee River BasinSuwannee River Basin Non-Structural Floodplain Non-Structural Floodplain

Management StrategyManagement Strategy

Floodplain RegulationFloodplain Regulation Floodplain AcquisitionFloodplain Acquisition Forecasting and EducationForecasting and Education

Floodplain Floodplain RegulationRegulation

Elevate StructuresElevate Structures Limit Fill and Obstructions in Limit Fill and Obstructions in

FloodplainFloodplain Riverbank Setbacks and Erosion Riverbank Setbacks and Erosion

ControlControl

Floodplain Acquisition Floodplain Acquisition StrategyStrategy

Provide natural storage for flood Provide natural storage for flood waterswaters

Reduce loss of life and property due Reduce loss of life and property due to floodsto floods

Protect ground and surface water Protect ground and surface water resourcesresources

Protect natural systems associated Protect natural systems associated with floodplain ecosystemswith floodplain ecosystems

Flood Warning and EducationFlood Warning and Education Emergency Management Emergency Management

CoordinationCoordination Flood Forecast ModelingFlood Forecast Modeling Forecast DisseminationForecast Dissemination– TelephoneTelephone– InternetInternet– NOAA Weather RadioNOAA Weather Radio

Georgia

Florida

FloodMonitoringNetwork in theSuwannee RiverBasin

USGS-GA

USGS-FL

Georgia

Florida

FloodForecastPoints in theSuwannee RiverBasin

USGS-GA

USGS-FL

Automated Automated RainfallRainfallNetworkNetwork

Current StationCurrent Station

Planned StationPlanned Station

Major Floods in the Suwannee Major Floods in the Suwannee BasinBasin

1928 - Earliest Documented Flood1928 - Earliest Documented Flood 1948 - Flood of Record on Alapaha, 1948 - Flood of Record on Alapaha,

Withlacoochee, Suwannee below Withlacoochee, Suwannee below EllavilleEllaville

1964 - Hurricane Dora - Flood of 1964 - Hurricane Dora - Flood of Record on Santa Fe RiverRecord on Santa Fe River

1973 - Flood of Record at White 1973 - Flood of Record at White Springs and Suwannee SpringsSprings and Suwannee Springs

1998 - Roughly a 20-year flood1998 - Roughly a 20-year flood

Recent Flood Events on the Recent Flood Events on the Santa FeSanta Fe

March/April 1991 - Last major March/April 1991 - Last major Suwannee flood before 1998 El NiñoSuwannee flood before 1998 El Niño

1992 – October Surprise 1992 – October Surprise February/March 1998 - Highest water in February/March 1998 - Highest water in

upper Santa Fe since 1964upper Santa Fe since 1964 March 2003 – NWSRFS Model Tune-upMarch 2003 – NWSRFS Model Tune-up

STAGE-STAGE RELATIONSHIPThree Rivers Estates and near Fort White

21 23 25 27 29 31 33Santa Fe River near Fort White

10/929/85 9/88

Pure Santa Fe Flood

4/84Pure Suwannee Flood

Mixed Flood

Monitoring GoalsMonitoring Goals Obtain near-real-time river level and Obtain near-real-time river level and

rainfall data for forecast model inputrainfall data for forecast model input

Improve our understanding of the Improve our understanding of the interaction between ground and surface interaction between ground and surface waterwater

Develop/maintain tools for evaluating Develop/maintain tools for evaluating changes in flow ratings in the changes in flow ratings in the Suwannee River BasinSuwannee River Basin

Rating MechanicsRating Mechanics

Primarily stage versus dischargePrimarily stage versus discharge Model mechanicsModel mechanics If stage-discharge relationship is If stage-discharge relationship is

unreliable, river forecast results will unreliable, river forecast results will be unreliable.be unreliable.

Sample River at Suchandsuch, FLFlow Rating Curve

0 1000 2000 3000 4000 5000 6000

Flow (cubic feet per second)

Rain, Soil Moisture, Travel Time

Rose Creek/Walter Little Road

Precipitation Depth-Duration-Frequency Table (rainfall amounts in inches)

ReturnPeriodin Years 1 day 2 day 3 day 4 day 5 day 6 day 8 day 10 day 30 day 60 day CAL YEAR

2 3.57 4.38 4.79 4.89 5.02 5.42 6.14 6.64 11.17 17.36 n/a5 4.87 5.99 6.51 6.74 6.97 7.46 8.23 8.93 14.2 21.43 n/a

10 5.73 7.01 7.59 8.05 8.45 8.96 9.63 10.54 16.11 24.1 n/a20 6.52 7.95 8.59 9.31 9.93 10.42 10.95 12.1 17.88 26.6 n/a25 6.77 8.24 8.9 9.71 10.4 10.89 11.37 12.6 18.42 27.38 n/a40 7.29 8.83 9.54 10.54 11.41 11.87 12.22 13.63 19.54 28.99 n/a50 7.53 9.11 9.83 10.93 11.88 12.34 12.63 14.12 20.06 29.74 n/a

100 8.26 9.95 10.73 12.15 13.36 13.77 13.85 15.61 21.64 32.03 n/a200 8.98 10.76 11.6 13.34 14.84 15.21 15.06 17.1 23.17 34.27 n/a

1000 10.59 12.59 13.54 16.09 18.28 18.51 17.78 20.5 26.6 39.33 n/a10000 12.83 15.08 16.2 19.97 23.19 23.2 21.58 25.3 31.28 46.34 n/a

PMP 24.86 30.88 33.06 35.27 37.67 39.18 40.42 44.22 61.01 84 n/a

Record 8 10.3 11.69 15.1 17.5 18.2 18.48 21.03 28.95 37.13 82.96 Maximum Record 1920 2004 1964 2004 2004 2004 2004 2004 2004 2004 1964 Year