USDA SSURGO COUNTY SOIL REFERENCE

Polk County, Iowa Soil Summary

This page summarizes USDA SSURGO mapped soil information for Polk County, Iowa.

Mapped Land Coverage
99.95%378,616.17 mapped acres of 378,808.56 Census land acres

Coverage measures mapped SSURGO intersection with Census land geometry. It does not mean that every parcel or point has complete soil information.

Soil at a Glance

Largest mapped soil unit
Bearden-Colvin silty clay loams, 0 to 2 percent slopes
Symbol: I123A2.51% of mapped area
Largest estimated component
Water
13,743.65 acres (3.63% of mapped area)
Mapped units & components
15 soil units • 15 component series
Distinct SSURGO map units & series
Dominant drainage class
Well drained
Highest acreage drainage class
Dominant hydrologic group
Group C
Runoff potential classification
Weighted average slope
8.23%
Terrain slope analysis
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County summaries provide regional context across mapped soil units. Address lookup combines available public datasets for the Census-matched location.

Mapped SSURGO Soil Units

Largest mapped soil units in Polk County ranked by intersected vector acreage
SymbolMap Unit NameMapped Acres% of Mapped Area
I123ABearden-Colvin silty clay loams, 0 to 2 percent slopes9,494.622.51%
17Smyrna and Myakka fine sands7,251.651.92%
PfBPinetucky fine sandy loam, 1 to 5 percent slopes6,998.351.85%
HatAHatliff-Pluck-Kian complex, 0 to 1 percent slopes, frequently flooded6,930.91.83%
3864Hastings silt loam, 0 to 1 percent slopes5,672.021.5%
99Water5,262.331.39%
I666AColvin-Perella silty clay loams, 0 to 1 percent slopes5,008.831.32%
3Candler sand, 0 to 5 percent slopes4,885.411.29%
7Pomona fine sand4,588.471.21%
DoBDoucette loamy fine sand, 1 to 5 percent slopes3,355.590.89%
WWater3,255.420.86%
31DSherless-Littlefir complex, 8 to 15 percent slopes, stony3,101.640.82%
WoDWoodville fine sandy loam, 5 to 12 percent slopes3,068.560.81%
13Samsula muck, frequently ponded, 0 to 1 percent slopes2,700.520.71%
15Tavares fine sand, 0 to 5 percent slopes2,689.790.71%

Estimated Soil Components

Component acreage estimated from SSURGO component percentages
ComponentDrainage ClassHydrologic GroupEstimated Acres% of Mapped Area
WaterSubaqueousD13,743.653.63%
ColvinVery poorly drained, Poorly drainedC/D, B/D8,087.362.14%
BeardenSomewhat poorly drainedC7,529.831.99%
PinetuckyModerately well drainedC7,159.261.89%
HastingsWell drainedC6,492.411.71%
SherlessWell drainedC6,255.071.65%
WoodvilleSomewhat poorly drainedD5,462.561.44%
CandlerExcessively drainedA5,083.591.34%
FullertonWell drainedB4,830.21.28%
SmyrnaPoorly drainedA/D4,340.331.15%
PomonaPoorly drainedA/D4,291.781.13%
RosholtWell drainedB, A3,828.431.01%
MyakkaVery poorly drained, Poorly drainedA/D3,792.531%
ClarionWell drainedB3,545.680.94%
ShackWell drainedC3,473.790.92%
Component acreage is estimated from SSURGO map-unit component percentages. Component values are not independently mapped polygon boundaries.

Drainage Class Distribution

Well drained36.01%
136,354.77 acres
Poorly drained16.86%
63,844.29 acres
Moderately well drained14.54%
55,059.19 acres
Somewhat poorly drained12.96%
49,081.02 acres
Very poorly drained6.17%
23,371.95 acres
Unknown / Unmapped6%
22,711.9 acres
Excessively drained3.61%
13,673.44 acres
Somewhat excessively drained2.66%
10,088.99 acres
Subaqueous0.04%
156.54 acres

Hydrologic Soil Group Distribution

Group C23.19%
87,795.09 acres
Group B18.67%
70,704.97 acres
Group D13.13%
49,713.62 acres
Group A11.62%
43,982.41 acres
Group C/D11.18%
42,345.05 acres
Group A/D8.92%
33,766.15 acres
Group Unknown / Unmapped6.5%
24,628.84 acres
Group B/D5.65%
21,405.93 acres

Hydrologic soil groups are USDA/NRCS classifications related to runoff potential under specified soil conditions. They are not a property-level flood-risk rating.

Slope Characteristics

Weighted Average Slope: 8.23%
Nearly Level (0-2%)43.41%
164,350.31 acres
Gently Sloping (2-8%)24.72%
93,588.25 acres
Moderately Sloping (8-15%)10.11%
38,263.62 acres
Steep (15-30%)9.27%
35,116.13 acres
Very Steep (>30%)6.43%
24,328.08 acres
Unspecified Slope4.94%
18,695.69 acres

Sources & Methodology

USDA NRCS SSURGO

Mapped soil units, components, drainage classes, hydrologic groups, and slope ratings derived from official Soil Data Access REST services.

U.S. Census Bureau TIGER/Line

County land geometry used for county-level coverage calculation.

Coverage Method

Mapped acreage is calculated from true spatial vector intersection of county land geometry and SSURGO mapped soil polygons using NAD83 / CONUS Albers Equal Area projection (EPSG:5070).