Soils C. Enright D. Hulse D. Richey

Data Sources Land Use Planning and Resource Management The map at right represents soils of the Willamette River Basin (WRB) Soil properties and characteristics are important considerations in ranked by land use capability classes, a general measure of the suitability of determining how land is used. Choices arise when land is well suited for soils for agricultural field crop production. Data from two of the United many uses. For example, attributes such as gentle slopes, availability of States Department of Agriculture (USDA) soil geographic data bases were water, and adequate drainage characterize many agricultural soils in the used to create the map: the Soil Survey Geographic data base (SSURGO) Willamette Valley and also make them valuable for building and urban and the State Soil Geographic data base (STATSGO). The most detailed development. information about soil properties is contained in SSURGO, data appropriate for use with areas ranging in size from an individual agricultural field up to The Oregon Department of Land Conservation and Development uses entire counties. SSURGO data are compiled using field observation methods soil capability classes to define Agricultural Land and High-Value Farmland or are based on aerial photography. STATSGO maps are designed for use in in Administrative Rule #660-033-0010-20 for implementation of Goal 3 in planning and natural resource management at a multistate or regional scale. Oregon’s Statewide Planning Goals (see p. 72). In western Oregon, Agricul- As shown in Figure 9, Map 2 contains data from both sources. STATSGO tural Land is defined as being soils predominantly in capability classes I-IV. data are coarser than SSURGO data, and are used only where SSURGO data High-Value Farmland includes all soils in capability classes I and II, and are unavailable. soils in subclasses IIIe, IIIw, IVe, and IVw. Land within acknowledged urban growth boundaries (UGBs) is not considered Agricultural Land and is exempt from Goal 3. Figure 12 and Table 2 show acreages of soil capability classes within the WRB and its 1995 UGBs. Component Name Salkum Capability Class Class II Hydrologic Group Group B Erodibility Factor (kffact) 0.28 Unknown Unknown 4% Class VIII 2% Class I Class I 2% 2% Class VIII 6% SSURGO Data Class VII 10% Class VII Class II Class I 1% 15% STATSGO Data 13% Class II Class VI Class III 6% Class III Figure 9. Areas of WRB described by SSURGO and STATSGO data. Each Class IV Class V Class II 12% < 1% SSURGO soil unit (polygon) represents a component that is associated with ClassV 38% Class VI Class IV 60 properties and 84 data elements such as hydrologic group and erodibility Class IV 14% 8% Class VII factor. Class VI Class V Class VIII 46% <1% Unknown Class III 21% Soil Classification Figure 10. Percentage of Figure 11. Percentage of soil Soil science provides a comprehensive taxonomic classification for soil capability classes capability classes inside 1995 soils. This scientific classification is based on underlying geology, and the within WRB. urban growth boundaries within formation processes, composition, physical structure, and chemical proper- WRB. ties of soils. Technical or interpretive classification systems consider specific land uses and management practices such as agricultural production, building development, and wildlife management. These are developed by experts in a UGB Class I Class II Class III Class IV Class V Class VI Class VII Class VIII Unknown Portland specific field through interpretation of the comprehensive taxonomic system. Metro 4,149 75,777 51,781 24,930 53 15,966 2,911 40,809 10,218 Salem 1,333 24,441 10,733 4,170 0 1,013 227 38 1,687 Corvallis- 900 6,505 3,785 7,547 0 1,188 52 0 584 The scientific classification system used by the USDA National Coop- Philomath Albany- 1,741 6,799 3,550 3,554 0 145 0 490 629 erative Soil Survey has six hierarchical levels of taxonomic classification: Millersburg order, suborder, great group, sub group, family, and series. A soil order, the Eugene- Springfield 10,686 13,788 6,558 10,6030 3,501 304 2,038 1,374 most general level, contains soils that have similar processes and degrees of Subtotal 18,809 123,310 76,406 50,804 53 21,813 3,495 43,375 14,492 formation. A soil series, the finest level of description, comprises soils with Other UGBs 6,909 42,207 18,334 9,648 0 5,752 181 1,827 2,805 similar composition and major soil horizons. UGB Total 25,718 165,517 94,740 60,451 53 27,566 3,676 45,202 17,297

Table 2. Acres of soil capability classes inside 1995 urban growth Map 2 at right depicts soils based on an interpretive classification boundaries within WRB. system designed to indicate the suitability of soils for agricultural crop Note: 2.47 acres equal one hectare. production. This system assigns a land use capability classification from I to VIII (this is also known as soil capability classification). Figures 10 and 11 show the percentage of these capability classes within the WRB and its 1995 urban growth boundaries. Class I soils present the fewest limitations and are 15,953 ac 123,714 ac1,067,395 ac910,815 ac611,264 ac 2,360 ac 3,413,659 ac960,207 ac1 139,223 ac the most suitable for agricultural crop production. As the capability classifi- 100% cation number increases, soil limitations increase and suitability for agricul- 80% Percentage tural crop production decreases. Soil capability is further described with the of soil class outside 1995 addition of subclass and unit labels. The most complete description of a soil 60% UGBs capability class is in the form IVe2. The Roman numeral indicates the degree of limitation, the lower case letter (subclass) describes the type of limitation 40% Percentage of soil class (e- erosion potential, w- wet soil, s- shallow soil) and the Arabic number inside 1995 20% (unit) characterizes appropriate crops and management practices. UGBs

Percentage of Soil Class in WRB 0% Soil Maps and Representation Maps represent soils as uniform areas with well-defined boundaries. As Class I Class II Class III Class IV Class V Class VI Class VII Class VIII Unknown with other land features such as vegetation and geology, soils can be hetero- Soil Capability Class geneous complexes without distinct boundaries. Soil map delineations represent the dominant soil type in an area, but, like all maps, may include Figure 12. Percentage of soil capability classes within and outside 1995 errors in classification and boundary position. urban growth boundaries in WRB. The numbers at the top of the chart represent the total number of acres for each soil capability class within WRB.

10 PNW Ecosystem Research Consortium LANDFORMS Map 2. Soils

121 45’00" 123°45’00" 123°37’30" 123°30’00" 123°22’30" 123°15’00" 123°07’30" 122°45’00" 122°37’30" 122°30’00" 122°22’30" 122°15’00" 122°07’30" 122°00’00" 121°52’30" ° 45°52’30" 45°52’30"

Saint Helens

Projection UTM Zone 10 Scale 1:750000 45°45’00" 45°45’00" 0 mi 10 mi 20 mi Scappoose

0 km 10 km 20 km 30 km 45°37’30" 45°37’30" Banks North Plains

Fairview Portland 84 Forest Grove Troutdale 45°30’00" Gresham 45°30’00" Beaverton 205

Milwaukie Happy Valley Gaston Tigard

Sandy Tualatin 45°22’30" 45°22’30" Sherwood Yamhill Oregon City 5

Carlton Newberg Wilsonville Estacada Dundee Canby 45°15’00" Lafayette 45°15’00" Aurora Dayton Donald McMinnville

Hubbard Woodburn Molalla 45°07’30" Sheridan Amity Gervais

Willamina Mt Angel

Scotts Mills

45°00’00" Silverton 45°00’00" Keizer

Dallas Salem

44°52’30" 44°52’30" Falls City Independence Aumsville Monmouth Turner Sublimity

Lyons Gates 44°45’00" 44°45’00" Mill City Detroit Jefferson Scio Idanha Millersburg Adair Village

44°37’30" Albany 44°37’30"

Corvallis Lebanon

Tangent 44°30’00" 44°30’00" Waterloo Sodaville

Brownsville Halsey Sweet Home 44°22’30" 44°22’30"

Monroe

Harrisburg

44°15’00" 44°15’00"

Junction City

Coburg 44°07’30" 44°07’30"

Veneta Eugene Springfield

44°00’00" 44°00’00" Class I Few limitations for agriculture Class II Moderate limitations for agriculture Creswell Lowell Reduce choice of plants or require moderate conservation practices 43°52’30" 43°52’30" Class III Severe limitations for I55 agriculture Reduce choice of plants and/or require special conservation practices Cottage Grove Class IV Very severe limitations for agriculture Westfir 43°45’00" Reduce choice of plants and/or 43°45’00" require very careful management Oakridge Class V Limitations for agriculture Use limited by considerations, other than erosion, that are impractical to remedy Class VI Severe limitations for agriculture Generally unsuitable for cultivation 43°37’30" Class43° 37’30"VII Very severe limitations for agriculture Unsuitable for cultivation Class VIII Unsuitable for agriculture Limitations nearly preclude use for cultivation

Water 43 30’00" 43°30’00" N ° Unknown

5 Interstate Highways S

199543 °Urban22’30" Growth Boundary 43°22’30" 121 45’00" 123°45’00" 123°37’30" 123°30’00" 123°22’30" 123°15’00" 123°07’30" 123°00’00" 122°52’30" 122°45’00" 122°37’30" 122°30’00" 122°22’30" 122°15’00" 122°07’30" 122°00’00" 121°52’30" °

Willamette River Basin Atlas 11 2nd Edition