S o i l S c i e n c e D i v i s i o n Soil Data for Riverbank Erosion August 30, 2018 | David Rand
What is SSURGO soil data? • Soil materials and layers • texture, rock fragments, depth, pH • Site characteristics • landform, slope, climate, potential vegetation • Location (maps) • Facilitates prediction and extrapolation of soil behavior • SSURGO database available online through Web Soil Survey • Intended for natural resource planning and management by landowners and counties • Scale is important
How is SSURGO soil data made? Fig. 3 from Soil Survey of Marion County Area, Oregon. https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/oregon/marionOR1972/marionOR1972.pdf
Soil Interpretations • Boil down the data • Evaluate suitability for particular soil uses • Based on rule sets • Web Soil Survey offers standard interpretations • E.g. “Shallow Excavations” evaluates • coarse material • shrink/swell • water table • A standard interpretation for wake erosion vulnerability hasn’t been developed yet • Need to investigate which soil properties translate to bank erosion vulnerability
Locating vulnerable soils… a preliminary interpretation Observation/Hypothesis: Soils exposed in cut banks vulnerable to erosion are silty or clayey. These soils are cohesive enough to form a vertical bank, but they may be gradually undermined until the bank collapses. • Soil data can’t test this hypothesis • Soil data CAN show the extent of silty or clayey soils
Locating vulnerable soils…a preliminary interpretation
Closing Thoughts • SSURGO soil data summarizes soil properties and site characteristics under natural conditions • Doesn’t account for man -made or recent manipulations • Rip rap, vegetation, channel geometry • Soil data should be interpreted based on tested rule sets as knowledge grows about wave erosion in the Newberg Pool • USDA-NRCS can continue to assist in accessing and arraying soil data
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