HEC-RAS and HEC-HMS Review

HEC-RAS and HEC-HMS Review

Continuous Hydrologic Simulation of Johnson Creek Basin and Assuming Watershed Stationarity Rick Shimota, P.E. Hans Hadley, P.E., P.G. The Oregon Water Conference 2011 Corvallis, OR Engineering Hydrology Often a minor project component Watershed stationarity typically assumed Historical data preferred methodology (look back) Regression equations Log Pearson III NOAA Atlas 2 2 Outline Background information

Purpose of study Watershed description Hydrologic Model Development Calibration Continuous Simulation Comparison of Model Results Lessons learned 3 Purpose of study To develop peak discharge-frequency estimates for revision to the FEMA Flood Insurance Study 10, 50, 100, and 500 year peak discharge estimates

18 small basins (< 4 mi2) hydrology for 29 points Current land use conditions 4 Johnson Creek Watershed Located in Portland Metropolitan area Mixed land use Study area approximately 26 mi2 Data rich 5 precipitation gages

18 61 years of hourly precipitation data 3 stream gages 9 23 years of hourly discharge data 69 years of annual peak flow data 5 Johnson Creek Watershed 6 Hydrology by Continuous Simulation Peak flow estimates of small watersheds with unique characteristics

Land use Soil Characteristics Watershed slope Data availability Statistical approach using current land use conditions 7 Peak Discharge Development Hydrologic Model Development Basin parameter development Calibration / Verification Continuous Simulation

Extract annual peak flow events Flood Frequency Analysis (Log Pearson III) on peak events 8 Hydrologic Model Development HEC-HMS Loss method Deficit and constant rate Simplified soil moisture accounting method Transform Method

Clark Unit Hydrograph Storage Component R Time of Concentration Tc Related by Constant C = R/(Tc + R) 9 Hydrologic Model Development Meteorological Data Five precipitation gages available 4 gages near or within watershed 18 33 years of hourly data Portland Airport precipitation gage

61 years of hourly data Pleasant Valley Station Pleasant Valley Annual precip (in) 80 y = 1.23x R = 0.80 70 60 50 40 30 20 10 0 0 10

20 30 40 50 Portland Airport annual precip (in) 10 60 70 Calibration Calibration storm event - January 2, 2009 Current land use conditions 3rd largest flow event of record

14-yr recurrence interval 11 Calibration 2500 USGS Gage 14211500 Johnson Creek at Sycamore 2000 Peak discharge (cfs) RunoffVolume (ac -ft) Observed Simulation 2,430 2,445 6,390 % difference +0.6 6,280

- 1.7 discharge (cfs) 1500 1000 500 0 31-Dec-08 1-Jan-09 2-Jan-09 3-Jan-09 simulated flow 4-Jan-09 observed flow

12 5-Jan-09 6-Jan-09 7-Jan-09 Calibration Results Peaks and volumes comparable at three gages Confident of model is a representation of basin rainfall-runoff process Limitation Not a base flow model 13 Continuous Simulation - Issues HEC-HMS / DSS data processing limitation

file size (~8 GB) 61 years broken into 10 year intervals Soil moisture recovery Direct function of ET only No deep infiltration Model calibrated to winter storm events Large events in summer 14 Limitation of loss method? FEMA Model Acceptance Hydrologic model 100-yr result must compare

within one standard error to other discharge frequency relationships USGS regression equations (NSS - urban equations) Log Pearson III analysis of stream gage data Comparison at USGS Gage 14211500 Downstream extent of study area 69 years of annual peak data 15 FEMA Model Acceptance Comparison of 100-yr peak discharges Regression equation 3,890 cfs (2,990

4,780 cfs) Log Pearson Analysis 3,300 cfs (2,490 3480 cfs) Simulation - 3,870 cfs 16 FEMA Model Acceptance Model results do not agree within one standard error of most reliable dischargefrequency relationship Assumption of stationarity valid?? Land use change Climate change? 17 Land Use Changes City of Gresham approximately 30% of basin area

1940 Population 1,951 2008 Population 101,221 120,000 City of Gresham Population (US Census) 100,000 80,000 Population 60,000 40,000 20,000 0 1940

1950 1960 1970 1980 18 1990 2000 2008 PDX Annual Precipitation record length 1950 2009 Average - 36.6 in/yr Last 30 years 35.4 in/yr Previous 30 years 37.7 in/yr 70

Portland Airport Annual Precipitation 60 annual precipitation (inches) 50 40 30 20 19 10 1950 1955 1960 1965

1970 1975 1980 year 1985 1990 1995 2000 2005 2009 FEMA Model Acceptance- Continued Comparison at USGS Gage 14211500

Assume hydrologic stationarity last 20 years of gage record Comparison of 100-yr peak discharges Log Pearson Analysis 3,580 cfs (2,990 3,990 cfs) Simulation - 3,870 cfs 20 Lessons Learned Stationarity Dead? Continuous Simulation acceptable approach Need for look forward hydrologic tools Standardized Simplistic Accepted


Recently Viewed Presentations

  • Romeo and Juliet Act One

    Romeo and Juliet Act One

    BENVOLIO At this same ancient feast of Capulet'sSups the fair Rosaline whom thou so lovest,With all the admired beauties of Verona:Go thither; and, with unattainted eye,Compare her face with some that I shall show,And I will make thee think thy...
  • Chapter 5

    Chapter 5

    Osmosis. Osmosis is the diffusion of WATER from high to low concentration. Direction of osmosis (water movement) depends on the relative concentration of . solutes. inside and outside the cell. Review: Solute —substance dissolved in water (Ex: sugar, salt) Solvent...
  • The Body of the Condemned - University of California, Davis

    The Body of the Condemned - University of California, Davis

    The Body of the Condemned Philosophy 157 G. J. Mattey ©2002 Discipline and Punish Published in 1975 Topic is the conversion from torture to mere confinement as punishment Sub-theme is the way in which bodies are regulated as the result...
  • Nerve activates contraction

    Nerve activates contraction

    Chapter 3 continued … PART bV. The Plasma Membrane-- Transport. Terms To Fill Into PPT prior to Class. semipermeable, solvent, solute, Intercellular, extracellular, and interstitial fluids
  • American Postal Workers Union ALL CRAFT CONFERENCE 2015

    American Postal Workers Union ALL CRAFT CONFERENCE 2015

    Likewise, PS Form 2609 will be made available, upon request, at Step 3 or any time thereafter. If any part of a video tape has been or is intended to be used as a basis for disciplinary action, those portions...
  • The Earth and it&#x27;s Layers - Suffolk City Public Schools

    The Earth and it's Layers - Suffolk City Public Schools

    The Earth and it's Layers. The Earth's Structure. A. Earth consists of a series of concentric layers or spheres which differ in chemical and physical properties. B. The compositional layers of the Earth are the Crust, the Mantle, and the...
  • Mining and Summarizing Customer Reviews

    Mining and Summarizing Customer Reviews

    Features that are domain synonyms should be grouped together. Many techniques can be used to deal with the problem, e.g., ... But notice again (a simplistic way): Some opinion words have context independent orientations, e.g., "great".
  • The Efficient Markets Hypothesis  Explained, Demythologized, Buried, and

    The Efficient Markets Hypothesis Explained, Demythologized, Buried, and

    1962 - Jack Treynor wrote his unpublished manuscript 'Toward a theory of market value of risky assets', the first paper on the Capital Asset Pricing Model (CAPM) 1963 - Granger and Morgenstern found that short-run movements of the series obey...