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

Alternate versions

  • None

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