Michael Schaffner, NOAA National Weather Service, Binghamton Weather Forecast Office

1. Real-Time Flash Flood Forecasting in Small Fast-RespondingWatersheds using a Distributed Rainfall-Runoff Model Michael Schaffner, NOAA National Weather Service, Binghamton Weather Forecast Office Carl L. Unkrich, Hydrologic Engineer, USDA ARS Tucson David C. Goodrich, USDA ARS Tucson Eastern Region Flash Flood Conference June 3, 2010

2. What are current National Weather Service (NWS) methods of providing site specific/basin specific services? • Flash Flood Monitoring and Prediction Program (FFMP) • Site Specific rainfall-runoff models • Headwater Guidance • Flash Flood Guidance

3. FFMP • This allows the forecaster to pinpoint (i.e. provide site specific information) which basins are receiving the heaviest rainfall. • Does not allow the forecaster in most cases to determine the timing and magnitude of an event.

4. Available Site Specific Model in the Middle Atlantic Region • Antecedent Precipitation Index (API) • One-hour time steps • Hourly Multi-Sensor Precipitation Estimator (MPE) input • Manual hourly QPF input

5. KINEROS (kinematic runoff and erosion model) • Distributed model. • Runs on a PC. • Event-based model. Not a continuous model. • Must be started up at about the start time of a heavy rainfall event. • Runs using finer time steps than available models. • Runs using precipitation resolution which is smaller in terms of spatial and temporal resolution than existing models. • Kinematic wave equations.

6. KINEROS Setup • Is accomplished by using the Automated Geospatial Assessment Tool (AGWA). • AGWA runs using ESRI GIS with Spatial Analyst. • Uses readily available GIS datasets which can be obtained free of charge. • Automated Geospatial Watershed Assessment (AGWA) Tool provided by USDA: • http://www.tucson.ars.ag.gov/agwa/

7. Schematic View Composed of a cascade of overland flow planes and open channel elements. Plan View Above image from: http://www.tucson.ars.ag.gov/kineros/

8. Precipitation Input • The Digital Hybrid Reflectivity Product (DHR). • DHR provides the highest resolution available in terms of temporal (every volume scan – 4 to 5 min.) and spatial (1 Km by 1 degree) scale. • DHR has a Z-R Relationship applied to it and quality control measures included within the PPS (e.g. for hail) to produce rainfall for KINEROS. • KINEROS requires DHR available in real time. • A new solution is generated every time a new volume scan of data comes in.

9. Field Work* / Data Collection • Required to collect average manning roughness for each open channel element. Manning roughness is defined as the average for each channel element. • Required to define up- and down-stream channel widths for each open channel element. *High resolution aerial imagery can also be used for width measurements,and in some cases, Manning n.

10. Starting up the model • Select initial flow rate • Select initial soil moisture state (very dry, dry, wet, or very wet) • Select date and time of simulation start • Select Z-R Relationship / QPF (optional)

11. KINEROS GUI

12. Platte Kill near Dunraven, NY • 35 square miles. • Tributary to the East Branch of the Delaware River. • Collected channel widths and manning roughness values at 19 locations. • Manning roughness varied from 0.030 to 0.042

13. Model Calibration Process • Involves manual calibration using parameter multipliers. • Parameter multipliers function on a global basis maintaining the relative differences across model elements. • Saturated hydrologic conductivity multiplier is used to calibrate the magnitude of the peak flow. • Channel length multiplier is used to calibrate timing of the peak flow.

14. Displaying calibration results… • Plotting model parameter multipliers as a function of maximum basin average rainfall intensity. • A linear regression line is fit to the data. • This allows a reasonable solution to be produced for a range of rainfall intensity values.

15. Typical Hydrographs for Platte Kill • Reasonable simulation of peak flow in terms of magnitude and timing. • Rapid rise in rising limb of hydrograph from gage data is likely due to saturation excess flow generation and lateral subsurface flow into channel which the model does not account for.

16. Lead Time: Beaver Kill near Cook Falls, NY 241 square mile fast responding headwater point. KINEROS can provide lead time of almost 3 hours on the flood crest vs. minimal lead time when compared to the typical flood warning issued. Further lead time is possible when QPF is added. USGS web cam image: http://ny.water.usgs.gov/rt/pub/01420500.htm

17. Ungaged Basins • Represent an unmet need in forecasting within the NWS. • Data can be collected on small basins using indirect discharge methods. • Timing of onset of flooding and peak flooding can be noted.

18. Callicoon Creek, NY Calibrated originally for the USGS stream gage at Callicoon. May not be representative of flooding further upstream along the East Branch at Jeffersonville.

19. Callicoon Creek at Jeffersonville Watershed in KINEROS

20. KINEROS Calibration Low R2 still allows “categorical” forecasting at Jeffersonville.

21. Summary of Current use of KINEROS • Used for gaged and ungaged basins. • Peak flow forecasting for gaged basins including some headwater river forecast points. • Peak flow forecasting for ungaged basins under the limitation of categorical forecasting.

22. Future Improvements • Develop best practices for the use of QPF in KINEROS. • COMET grant with University of Arizona, USDA-ARS, and Penn State to couple a sub-surface lateral flow model and snow model with KINEROS.

23. Questions / Comments?