Download soil_BMPs - Iowa State University

Iowa BMPs
for soil erosion prevention
BMP context
• BMPs needed for
managed land (duh!)
• Strategies differ by landuse
– Ag/crops (>71%)
• +/- CRP, etc
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Ag/pasture (9%)
Developed (5%)
Timber (5%)
Other (8%)
• Grassland, wetland, open
water, etc.
Source: ISU Extension
Source: Iowa Daily Erosion Project – dailyerosion.org
Source: ISU Extension
Source: ISU Extension
Upland soil erosion: PREY
• Precipitation fate
– Intensity, duration, interception/ET
• Runoff routing
– Volume, depth, concentration, roughness
• Erosion
– Soil properties vs. flow competence, capacity;
drag partitioning
• Yield
– Delivery or deposition
Soil-related BMP highlights
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Protect soil with ground cover
Promote infiltration on-site
Impede generated runoff
Inhibit sediment delivery
• Reflected in C and P factors in *USLE
• Green-Ampt parameters, friction factors,
threshold stress, and structural features in
physical models
Forest land BMPs (1)
• Site characterization
Map:
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Soils
Land cover
All streams
Drainage patterns
Topography and slope %
Wetlands
Archaeological sites
Adjoining land use
T&E species
• Planning
– Identify SMAs(SMZs)
– Locate landings
– Locate haul roads & skid
trails
– Identify stream crossings
– Secure necessary permits
– Develop management plan
– Schedule operations to
minimize impact
– Maintain on-site spill kit
– Identify soil BMPs
Forest land (2)
• Streamside management
areas (SMAs; SMZ in
other states) [50-150 ft
wide]
– Exclude livestock
– Avoid landings, limit
wheeled traffic in SMAs
– Minimize disturbance of
ground cover/soil
• Roads
– Minimize number, width,
length
– Avoid SMAs except at
(minimized) crossings
– Road grades < 5%
• Harvest Operations
– Use frozen ground if
possible
– Limit skid trail number and
length
– Winch logs on steep slopes
– Refill ruts
Agricultural land BMPs
CROPLAND
In-field vs. edge-of-field
• Contour farming
• Terraces
• No-till/reduced tillage &
residue management
• Cover crops
• Grassed waterways
• Perennial vegetation
plantings (e.g., STRIPs)
• Riparian buffers
PASTURE / GRAZING LAND
• Livestock exclusion
– From waterways/wetlands
– From riparian buffers
• Rotational grazing
Urban land / Construction sites
• Non-structural and
structural BMPs
• Goals
– Promote infiltration
– Reduce runoff
– Inhibit erosion/protect
soil/fill
– Containment
• Structural BMPs
– Infiltration systems (e.g.,
“rain gardens”,
permeable surfacing)
– Dissipative conveyances
– Stormwater detention
basins
– Filtration systems:
vegetative, granular,
synthetic
Q: What happens when erosion
management focuses only on capturing
sediment, but not controlling runoff?
Dangers / traps
soapbox warning
• Don’t forget water mass balance
• Everything you do impacts everything else…
…downslope
• Once infiltration is reduced, everything gets
worse (BMP tradeoffs)
• Pipes/armored conduits/waterways move
problem downslope (conveyance should not be
an end goal)
• Today’s 100-year event is tomorrow’s 10-year
event