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Brian Cosgrove

Brian Cosgrove Collaborators: Seann Reed, Michael Smith , Feng Ding, Yu Zhang, Zhengtao Cui, Ziya Zhang NOAA/NWS/OHD. Distributed Modeling DHM-TF: Monitoring and Predicting Flas h Floods with a Distributed Hydrologic Model Eastern Region Flash Flood Conference June 3 rd 2010. Photo: NOAA.

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Brian Cosgrove

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  1. Brian Cosgrove Collaborators: Seann Reed, Michael Smith, Feng Ding, Yu Zhang, Zhengtao Cui, Ziya Zhang NOAA/NWS/OHD Distributed ModelingDHM-TF: Monitoring and Predicting Flash Floods with a Distributed Hydrologic ModelEastern Region Flash Flood ConferenceJune 3rd 2010 Photo: NOAA Distributed ModelingDHM-TF: Monitoring and Predicting Flash Floods with a Distributed Hydrologic ModelEastern Region Flash Flood ConferenceJune 3rd 2010 Brian Cosgrove Collaborators: Seann Reed, Michael Smith, Feng Ding, Yu Zhang, Zhengtao Cui, Ziya Zhang NOAA/NWS/OHD

  2. Focus:Leveraging distributed modeling to more effectively analyze and predict flash flooding • Hydrologic Modeling: Distributed versus lumped • Overview of OHD’s Distributed Hydrologic Model Threshold Frequency (DHM-TF) flash flood application • DHM-TF Precipitation forcing data • Visualization and interpretation of DHM-TF data • DHM-TF Flash flood case studies • Summary and future plans Outline:

  3. Lumped Versus Distributed Models Distributed models are well-suited for flash flood prediction and monitoring, offering high-resolution streamflow at outlet and interior points with ability to route flow Distributed Lumped • Rainfall, soil properties vary by grid cell • Rainfall/runoff model applied separately to each grid cell • Prediction/verification at any grid cell • Advantages over lumped—cell-to-cell routing, higher resolution, ingest gridded observations • Rainfall and soil properties averaged over basin • Single rainfall/runoff model computation for entire basin • Prediction/verification at one point 3

  4. DHM-TF: An application of distributed modeling • What is DHM-TF? • A generic approach to leverage strengths of distributed modeling and statistical processing to monitor and predict flash floods • Provides way to cast flood severity in terms of return period by converting model flow forecasts to frequency (return period) • Similar approach to that used/developed at CBRFC • Why this method? • Fills gaps in existing flash flood tools (routing, rapid updates, interior pts) • Return periods directly relate to existing engineering design criteria • Resistance to uniform bias in modeled flow (only rankings used) DHM-TF Distributed Hydrologic Model Frequency Post Processor Gridded Discharge Gridded Frequency (Return Period)

  5. DHM-TF Ingests MPE, HPE, and HPN Precipitation MPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009 HPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009 Observations 1-2 Hour HPN Forecast (mm) 23Z April 21st to 00Z April 22nd 2009 0-1 Hour HPN Forecast (mm) 23Z April 21st to 00Z April 22nd 2009 Forecasts

  6. DHM-TF Output DHM-TF Discharge (m3/s) DHM-TF Return Period (Years) • Both discharge and return period output available • Return period superior for flash flood depiction • Resistance to bias in flow values versus raw discharge • Relates directly to existing engineering design criteria

  7. Interpreting DHM-TF Output Compare DHM-TF Return Period Map -with- Return Period Threshold Map Return Period (Years) DHM-TF Output Return Period (Years) Uniform 2-Year Value Spatially Varying Values (Generated from local knowledge, engineering design criteria) Superior Choice: Better-reflects actual channel conditions Flooding judged to occur in grid cells which exceed two year return period -or- Flooding judged to occur in grid cells which exceed values on varying threshold map 7

  8. DHM-TF Performance Photo credit: NOAA APRFC • Factors leading to good DHM-TF simulations: • Temporally static (or zero) model flow bias • Hydrologic model which accurately represents flow distribution • Adequate length of underlying precipitation record (need ≥ 10 years) • High-quality precipitation forcing data • Good fit of Log Pearson Type III distribution to actual flow values • Few instances of water regulation in simulation domain • Skill of end-user • Interpretation of return period map affected by local knowledge • Low water crossings • Vulnerable infrastructure • Well-protected / highly engineered areas • Water regulation structures 8

  9. Current Status of DHM-TF • How is DHM-TF currently implemented? • Sacramento model with kinematic wave routing…but generic approach which can be applied to any distributed model • Executed with and without cell-to-cell routing • DHM-TF pilot studies are underway in coordination with NWS Weather Forecast Offices (WFOs) and River Forecast Centers (RFCs) • DHM-TF executed over Baltimore/Washington WFO domain on OHD server • Pittsburgh WFO domain DHM-TF simulation run on Pittsburgh WFO server • Imminent expansion to Binghamton WFO domain (on BGM server) Pittsburgh, Binghamton, and Balt/Wash WFO Domains Binghamton 57,500 km2 89,000 km2 Balt/Wash Pittsburgh 11,000 km2

  10. Real-time Pittsburgh DHM-TF Prototype Return Periods Calculated Optional HPN No Precipitation OHRFC MPE (4km, high confidence) OHRFC MPE or PBZ HPE Model States Saved Switch Time T-24 hrs T-23 hrs Present T+3 hrs T+1 hr DHM-TF Run 2 (forecast run) DHM-TF Run 1 (state update) *Cycle automatically repeated every hour in current setup

  11. DHM-TF Verification • Two flash flood case studies from the Pittsburgh WFO • August 9th-10th, 2007: 25 flash flood warnings issued, large event with two waves of rain • March 22nd-23rd, 2010: 4 flash flood warnings issued, smaller event • Following slides will detail several comparisons: • Location of spotter-reports versus DHM-TF output • DHM-TF output with and without cell-to-cell routing • Model-produced flow versus measured USGS stream gauge flow • DHM-TF timing versus timing of WFO flash flood warnings • Highlights: • Good overall results versus observations • Cell-to-cell and local routing each have unique strengths

  12. DHM-TF Verification: August 9th, 2007 Flash Flood Maximum DHM-TF Return Period Values (Years) 12Z 8/9/07 through 12Z 8/10/07) • Overall, good match between areas of high DHM-TF return periods and spotter-reported events (wave symbols) • Local routing performs slightly better than cell-to-cell routing • Difficult to determine storm report location Standard Cell-to-Cell Routing Local Routing (only internal cell routing) Reported Flash Floods

  13. DHM-TF Verification: August 9th, 2007 Flash Flood Pittsburgh Area DHM-TF maximum event return period difference plot (years) over 12Z 8/9 to 12Z 8/10 time period Computed as: Local Routing minus Cell-to-Cell Routing Reported Flash Floods Local routing yields higher return periods over main stem rivers, better representing flash floods in pixels that include large channels 13

  14. Girty’s Run dischargewith input precipitation derived with standard Z-R relationship Local = Only internal cell routing Std = Standard cell-to-cell routing Precipitation forcing greatly impacts modeled flows Girty’s Run discharge withinput precipitation derived with tropical Z-R relationship Local = Only internal cell routing Std = Standard cell-to-cell routing 14

  15. DHM-TF Verification: August 9th, 2007 Flash Flood NWS FF Warning NWS FF Warning • County-wide comparison of DHM-TF with FF warnings • Simulations used MPE data • NWS Flash flood warnings • Westmoreland County (3 issued, 3rd not verified) • Allegheny County (4 issued, 4th not verified) • DHM-TF peaks (and time above 2 year return period threshold) agree well with verified warning periods • Local routing performs better toward end of event

  16. DHM-TF Verification: March 22-23, 2010 Flash Flood DHM-TF Return Periods (Years) at 12Z on March 23rd, 2010 Pittsburgh WFO-Issued Warnings and Spotter-Reported Flash Floods Standard Routing Option Local Routing Option PBZ WFO: Use of cell-to-cell routing enabled accurate depiction of flood extent FF FF 3/22 23:59Z – 3/23 03:00Z 3/22 23:42Z – 3/23 02:45Z 3/23 13:48Z – 3/23 22:45Z AF FF FF 3/22 23:42Z – 3/23 03:45Z 3/23 01:09Z – 3/23 07:15Z Reported Flash Floods FF = Flash Flood Warning AF = Areal Flood Warning

  17. DHM-TF: Summary and Future Work • Summary • DHM-TF: Combines distributed hydrologic model with threshold frequency post-processor  return periods • Capitalizes on strengths of distributed modeling • Fills gaps in existing flash flood tools (routing, rapid updates, interior pts) • Collaborative development and promising assessment effort • Future Work • Validation and deployment at additional field locations • Operation at higher temporal and spatial resolutions • In-depth validation using NSSL SHAVE data • Collaborative Assessment…Further refine DHM-TF to better match the needs of forecasters

  18. Thank You

  19. Extra slides that follow are only for reference if needed

  20. Return Period Calculation probability p(y) LP3 Probability Distribution Cumulative LP3 Probability Distribution • Distributed model outputs flow within each grid cell (m3/s) • Method needed to translate flow into return period • DHM-TF uses Log Pearson Type III (LP3) procedure • Established procedure with good availability of supporting data sets • Create probability distribution curve for each grid cell from log of annual max flow values (over ≥ 10 years) • Mean, standard deviation, and skew of flow data control shape of curve • Use cumulative probability distribution and flow for each grid cell to compute annual exceedance probability (AEP) and return period (1/AEP) • Procedure is automated within DHM-TF subroutines

  21. Specifics: OHD Research Distributed Hydrologic Model (RDHM) Precipitation Temperature Potential Evaporation Snow17 Snow Model rain + melt Sacramento Soil Moisture Model surface/impervious/direct runoff base flow / interflow Hillslope Routing (delays within-cell flow into channel) Cell-to-Cell Channel Routing *** Currently, full version only available as separate package from OHD (not within AWIPS) but will eventually be integrated in upcoming Community Hydrologic Prediction System (CHPS). Flows and State Variables Optional DHM-TF Flash Flood Post Processor

  22. Distributed Model Overview = Basin boundary = Model grid cell • RDHM ingests temperature, precip, and PE and produces discharge, soil temperature and soil moisture at each cell • Routes flow between cells via channel network • Accurately reflects impact on flow (timing/magnitude) of non-uniform precipitation • Produces verifiable discharge values at any location (including interior points.) • HRAP (16km2) resolution most common, but ½ and ¼ HRAP are future possibilities = Channel network Various types of output locations = Outlet Point = Interior Point = Headwater Point

  23. Distributed Modeling for Improved River Forecasts Model Parameters Heavy Rain Rainfall Application of OHD Distributed Model to Blue River, OK April 3, 1999 Surface Runoff Flow Direction

  24. Distributed Modeling for Improved River Forecasts 200 160 120 80 40 0 4/3/99 0:00 4/3/99 12:00 4/4/99 0:00 4/4/99 12:00 4/5/99 0:00 4/5/99 12:00 4/6/99 0:00 200 160 A 120 80 40 B 0 4/3/99 0:00 4/3/99 12:00 4/4/99 0:00 4/4/99 12:00 4/5/99 0:00 4/5/99 12:00 4/6/99 0:00 200 Blue River, Oklahoma 160 120 80 40 0 4/3/99 0:00 4/3/99 12:00 4/4/99 0:00 4/4/99 12:00 4/5/99 0:00 4/5/99 12:00 4/6/99 0:00 Hydrologic Response at Different Points in the Blue River Basin Distributed Lumped Observed Hydrograph at Location A Flow (CMS) • Lumped model output limited to basin outlet, distributed model able to output at interior points • Lumped model underestimates and delays peak at outlet due to basin averaged precip • Distributed model captures spatial variability and produces better simulation Hydrograph at Location B Flow (CMS) Heaviest Rain O Hydrographs at Basin Outlet (O) Flow (CMS)

  25. Current DHM-TF Requirements • Model operation • OHD RDHM software package (obtain from NWS LAD) • Operating System: Red Hat Enterprise Linux 4.0 • Compiler: GNU GCC/G++ 3.4.6 or later and PGF90 4.1-2 • Software Libraries • C++ BOOST library 1.36.x • GNU Scientific Library (GSL) 1.6 or later • Miscellaneous • Autoconf 2.13 • Automake 1.4-p5 • GNU Make 3.79.1 • RDHM Supporting data sets • Meteorological: Precipitation (long-term ~10 years, quality controlled), potential evaporation (can use monthly climatology), temperature (if using Snow17) • Parameters: Can often use pre-defined a priori data sets as solid starting point • Visualization of output • Google Earth (KML) • Google Earth software (runs best on PC, Pro version ingests shapefiles) • xmrgtoasc and a2png conversion utilities, luxisr.ttf font, Linux zip utility • Simple PNG image • GRASS GIS

  26. Sterling WFO DHM-TF Prototype Sterling WFO DHM-TF Domain Domain = 11,000 km2 DHM-TF with cell-to-cell routing currently running in real-time on OHD server over LWX WFO domain Analyzed June and September 2009 flash flood events with both cell-to-cell and local routing simulations Monitoring real-time DHM-TF simulations

  27. DHM-TF Verification: August 9th, 2007 Flash Flood PBZ WFO CWA outlined in red Warned counties outlined in green DHM-TF domain covers shaded area MPE Precipitation (mm) 12Z 8/9 to 12Z 8/10 Warned counties outlined in green Wave symbol indicates reported flash flood • Three mesoscale convective systems caused widespread flooding over Ohio, Pennsylvania, West Virginia, and Maryland • 25 Flash flood warnings issued by Pittsburgh WFO 12Z 8/9 to 02Z 8/10 • 24 Reported flash flood events • 10 Flash flood warnings with no corresponding reported event in county • Verification: Difficult to determine storm report location

  28. Girty’s Run Discharge USGS Gauge at Millvale Modeled flows (using local and cell-to-cell routing options) are too small in magnitude Precipitation input was too small (PBZ WFO has provided updated precipitation) Two HRAP pixels cover Girty’s Run (upstream pixel and pixel at gauge)

  29. DHM-TF Precipitation Forcing: Multisensor Precipitation Estimator (MPE) Data MPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009 • Characteristics • Several hour latency time may exist due to repeated manual adjustments and quality control of input fields as additional gauge reports are received • Latency makes real-time use in flash flood forecasting impractical • Description • One hour temporal resolution, 4km spatial resolution, > 1 hour latency • Uses a combination of radar, gauge, and satellite rainfall estimates • Production • Produced in AWIPS environment by each field office • Bias correction factors developed from a comparison of radar and gauge data • Bias-corrected radar blended with gauge-only field to produce merged radar/gauge product ~18 pixels within City of Baltimore

  30. DHM-TF Precipitation Forcing: High Resolution Precipitation Estimator (HPE) HPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009 • Description • Sub-hourly temporal resolution, 1km spatial resolution, < 1 hour latency • Uses radar rainfall estimates • Production • Produced in AWIPS environment at each field office • HPE leverages recent MPE gauge/radar bias information to automatically generate radar-based rainfall and rain rate products statistically corrected for bias • A user-defined radar mask determines how overlapping radars will be blended for each pixel within domain of interest • Characteristics • No manual quality control • Low latency, and high spatial/temporal resolution makes real-time use practical for flash flood forecasting ~72 pixels within City of Baltimore

  31. DHM-TF Precipitation Forcing: High Resolution Precipitation Nowcaster (HPN) HPN 15 minute precipitation forecasts (mm) out to 2 hours • Description • Sub-hourly temporal resolution, 4km spatial resolution, 1 hour (operational) or 2 hour (research) forecast lead time • Production • Dependent on HPE, produced in AWIPS environment at each field office • Local motion vectors are derived through a comparison of radar rain rates spaced 15 minutes apart, and are used to project current radar echoes forward in time out to two hours • Rain rates are then variably smoothed by a method based on the observed changes in echo structure over the past 15 minutes, as well as the current observed rain rate field • Characteristics • High spatial/temporal resolution well-suited for flash flood forecasting

  32. Bias Correction of Precipitation Monocacy at Jug Bridge (2116 km2) Cumulative Bias, Monocacy River at Jug Bridge (2100 km2) • Time-changing bias detected in MARFCMPE archives prior to 2004 • Bias corrected precipitation needed to support unbiased simulation statistics for a reasonable historical period (~10 years) • Analysis of Monocacy River flow shows reduction in cumulative bias and improved consistency when bias corrected precipitation is used • Consistent bias can be removed through calibration or addressed through DHM-TF approach

  33. Bias Correction of Precipitation Monthly RFCMPE Precipitation 03/97 (mm) Monthly PRISM Precipitation 3/97 (mm) RFC Hourly MPE Precipitation 03/01/97 12z (mm) Adjusted RFC Hourly MPE Precipitation 03/01/97 12z (mm) Monthly Bias (ratio, log scale) Key end result: time-changing, inconsistent precipitation biases are removed

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