Green-Ampt Parameterization for Rainfall Excess Determination

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

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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) - PowerPoint PPT Presentation

Transcript of Green-Ampt Parameterization for Rainfall Excess Determination

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Green-Ampt Parameterization for Rainfall Excess

Determination

Harry Downing

SWFWMD

April 18, 2008

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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

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Rainfall Excess Process

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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

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Soil Survey Information

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Soil Survey Information Continued

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Soil Moisture for 200 cm Depth to WTH

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Soil Moisture Content %

Soil Moisture

Saturation / Soil Porosity

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Soil Look-Up Table

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Land Use Look-up Table

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Creative Land Use Look-Up Table

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ESRI ArcHydro Tools

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ESRI Sub-Catchment Assignment of GA Parameters

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Questions?

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Infiltration and Percolation Parameterization

Take You Through Process that the District has Used

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Parameters Generation

1. Area Of Unsaturated and Saturated Infiltration

2. Perimeter Development

3. Hydraulic Properties of the Soil

4. Expected Depth to the Water Table (SHGWT or Higher)

5. Development of Parameters for Input Into ICPR

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Area of Infiltration

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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

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Hydraulic Properties of Soils

• SSURGO and IFAS Data• ERP Information• Geotechnical Information Reports• Soil Testing

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Location of Soil Bores Within Hernando County

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Vertical Hydraulic Conductivity Results

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Results from ERP Tests

SSURGO Results for Hydrologic ‘A’ Soils

• Minimum Value 0.028 inches/hr

• Mean 21.25

• Max 35 inches/hr

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Assumptions

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

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Depth to SHGWT

• Use SSURGO

• Potentiometric Surface Map

• Land Use Map

• Imagery

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ICPR Parameterization

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ICPR Parameterization Continued

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Questions?

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Floodplain ResultComparisons

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Stage Plot Comparison at Node

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Stage Plot Comparison at Node

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Stage Plot Comparison at Node

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Reasonableness of Floodplain

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ITEMS TO CHECK !!

• Double Accounting - Between GA, and Infiltration and Percolation

• Area of Influence Around Infiltration Areas

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Questions?