Iowa BMPs for soil erosion prevention

BMP context BMPs needed for managed land (duh!) Strategies differ by land- use – Ag/crops (>71%) +/- CRP, etc – 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

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 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: – 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) [ 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