Saturated Soils Needed

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Saturated Soils Needed. Water is initially drawn into soil by gravity and capillary forces. Runoff occurs once the soil is saturated and rainfall exceeds infiltration rates. How quickly this occurs depends on the soil…. R. A. McLaughlin. NCSU Soil Science. - PowerPoint PPT Presentation

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Saturated Soils NeededWater is initially drawn into soil by gravity and capillary forces.Runoff occurs once the soil is saturated and rainfall exceeds infiltration rates.How quickly this occurs depends on the soil

NCSU Soil ScienceR. A. McLaughlinSoil Infiltration Rates Decline Over Time

NCSU Soil ScienceR. A. McLaughlinRaindrops: The Start of ErosionTIME: 0 sec 1/1400 1/150 1/70From Hillel 1998Crater formedSoil is displacedDisplaced soil is depositedRain droplet falls on saturated soil.NCSU Soil ScienceR. A. McLaughlinSlope Makes Big DifferenceTIME: 0 sec 1/1400 1/150 1/70From Hillel 1998Soil is displacedDisplaced soil is deposited,farther downslope than upslopeNCSU Soil ScienceR. A. McLaughlinActual Droplet Splash on Saturated Soil

NCSU Soil ScienceR. A. McLaughlin

Splash Has Removed Fine Materials, Left RocksNCSU Soil ScienceR. A. McLaughlinSurface Sealing and CrustingRain droplets break down aggregates, sort the soil.Smallest particles form layer on surface.Infiltration rates decline 10X, often after only one storm.A crust forms as the soil dries.NCSU Soil ScienceR. A. McLaughlinSoil ErodibilityAll Soils Are Not Created EqualTexture or Particle Size DistributionSilt is the most easily eroded component.Clay tends to remain bound in the soil structure. Once caught up in runoff, it is very difficult to settle out.Sand promotes infiltration, reducing runoff volume, and tends to settle quickly.Organic Matter: increases infiltration so runoff volumes are lower.

NCSU Soil ScienceR. A. McLaughlinSoil Erodibility (cont.) All Soils Are Not Created EqualStructureBlocky, platy, or massive are less erodible than granular.

PermeabilityRapid is less erodible than slow!NCSU Soil ScienceR. A. McLaughlin

Creedmoor Sandy LoamSandy LoamSandy Clay LoamClay NCSU Soil ScienceR. A. McLaughlin

Erodibility Changes With DepthNCSU Soil ScienceR. A. McLaughlin

BIOTITE GNEISSPlottEdneyville-ChestnutTuskasegeeDellwoodTuckasegeeGRANITEWayahClimate, Landscape Position and Parent Material Affect Soil CharacteristicsNCSU Soil ScienceR. A. McLaughlin

Soil Erodibility (K) Calculation% Silt/Very Fine Sand% OMStructurePermeability% SANDNCSU Soil ScienceR. A. McLaughlin