Carneros Watershed: Map of Soil Erodibility Index

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Carneros Watershed: Soil Erodibility Index Map

Metadata

  • Original source of data: SSURGO
  • Data analysis: Fred Watson and Kathy Pugh
  • Map produced by: Kathy Pugh
  • Map produced using: ArcMap
  • Coordinate system: Geographic Coordinate System - GCS_North_American_1983
  • Datum: D_North_American_1983

Data Analysis Steps Taken

  1. 1. Download SSURGO data
  2. 2. Receive zip file of zip files, each one like soil_ca069.zip.
  3. 3. Extract, and open basic shapefile of map-units (MU): soilmu_a_ca069.shp in Arc
  4. 4. Can't read tables in this zip, because need special MS Access Template
  5. 5. Download Access template from http://soildatamart.nrcs.usda.gov/templates.aspx
  6. 6. Open template in Access; Enable Macros; and it should prompt for location of your tables
  7. 7. Wait a few minutes while Access imports your tables
  8. 8. Create some custom queries in Access to extract some kind of Kf for each map unit
    1. 8a. Review the SSURGO data model: http://soildatamart.nrcs.usda.gov/documents/SSURGO_2_2_DataModel_Part_1.pdf
    2. 8b. Each MapUnit contains several Components, each containing several Horizons.
    3. 8c. First query selects the surface horizons:
    4. 8c1 - it joins tables muaggatt+component+chorizon,
    5. 8c2 - joining on keys mukey and cokey
    6. 8c3 - selecting only horizons whose hzdept_r is 0 (i.e. surface horizons)
    7. 8c4 - includes the kffact (Kf-factor) and comppct_r (Percentage of map-unit occupied by Component) fields that will be used below
    8. 8d. Second query takes first as input, and is a MakeTable query, making the table that will be used in Arc
    9. 8d1 - computes an expression 'yournamekf: Sum([comppct_r]*[kffact]/100)'
    10. 8d2 - it is a Summation query, and the Summation is done on the fredkf field (above)
    11. 8d3 - the other two fields are musym and mukey, and they are GroupBy fields
    12. 8e. RUn the second query; it will make a table
    13. 8f. Export the table to DBF format (one way of getting it to Arc)
  9. 9. Back in Arc, add the DBF table as a layer
  10. 10. Join the soilmu_a_ca069.shp layer to the DBF layer, using the mukey
  11. 11. Change the soilmu_a_ca069.shp symbology to display quantitative based on the yournamekf field

Alternate versions

  • None

Links

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