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Green-Ampt Parameterization for Rainfall Excess Determination

Green-Ampt Parameterization for Rainfall Excess Determination. Harry Downing SWFWMD April 18, 2008. Green-Ampt (GA) Parameter Outline. The District has changed to GA? GA Process (General) Data Sources for Developing GA Parameters Look-Up Table Development (Soils and LU)

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Green-Ampt Parameterization for Rainfall Excess Determination

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  1. Green-Ampt Parameterization for Rainfall Excess Determination Harry Downing SWFWMD April 18, 2008

  2. Green-Ampt (GA) Parameter Outline • The District has changed to GA? • GA Process (General) • Data Sources for Developing GA Parameters • Look-Up Table Development (Soils and LU) • ArcHydro Tools for GA • Parameter Generation • Questions

  3. Rainfall Excess Process

  4. Soil Parameter Sources • NRCS - ‘Soil Survey’ and Soil Survey Geographical (SSURGO) Database - Depth to Water Table and Ksat • IFAS - ‘Site Specific Soil Characterization’ – Soil Moisture Retention Information • Table Information from Other Studies (Text Books) • Site Specific Characteristics from ERP Applications

  5. Soil Survey Information

  6. Soil Survey Information Continued

  7. Soil Moisture Saturation / Soil Porosity Height Above Water Table Centimeters Soil Moisture Content % Soil Moisture for 200 cm Depth to WT

  8. Soil Look-Up Table

  9. Land Use Look-up Table

  10. Creative Land Use Look-Up Table

  11. ESRI ArcHydro Tools

  12. ESRI Sub-Catchment Assignment of GA Parameters

  13. Questions?

  14. Infiltration and Percolation Parameterization Take You Through Process that the District has Used

  15. Parameters Generation • Area Of Unsaturated and Saturated Infiltration • Perimeter Development • Hydraulic Properties of the Soil • Expected Depth to the Water Table (SHGWT or Higher) • Development of Parameters for Input Into ICPR

  16. Area of Infiltration

  17. Area of Unsaturated Infiltration • First Make a Run with the GA Excess Option Only • Obtain the Maximum Inundation Area and Elevation from the Model Results • Develop a GIS feature class of the Inundation areas (area & perimeter) - units • Use this Information for the Infiltration and Percolation Parameters for ICPR regarding initial area

  18. Hydraulic Properties of Soils • SSURGO and IFAS Data • ERP Information • Geotechnical Information Reports • Soil Testing

  19. Location of Soil Bores Within Hernando County

  20. Vertical Hydraulic Conductivity Results

  21. Results from ERP Tests SSURGO Results for Hydrologic ‘A’ Soils • Minimum Value 0.028 inches/hr • Mean 21.25 • Max 35 inches/hr

  22. Assumptions • Horizontal Hydraulic Conductivity Greater Than Vertical • Use of Vertical for Horizontal Should be Conservative

  23. Depth to SHGWT Use SSURGO Potentiometric Surface Map Land Use Map Imagery

  24. ICPR Parameterization

  25. ICPR Parameterization Continued

  26. Questions?

  27. Floodplain ResultComparisons

  28. Stage Plot Comparison at Node

  29. Stage Plot Comparison at Node

  30. Stage Plot Comparison at Node

  31. Reasonableness of Floodplain

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