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3.4 Wind Erosion, Sediment Transport, Climatic Erosivity, and Resource Impacts
Free CESSWI Certified Erosion, Sediment and Stormwater Inspector Study Guide 2026 Exam
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1 Chapter 1: CESSWI Program Overview, Scope of Practice & Professional Ethics
1.1 CESSWI Scope of Practice, Eligibility, and Exam Structure 1.2 Certification Renewal, PDH Requirements, and Audit Policies 1.3 EnviroCert Code of Ethics and Professional Conduct
2 Chapter 2: Federal, State, and Local Stormwater Regulations
2.1 Federal Water-Pollution History and Stormwater Phases 2.2 CWA Sections, Water Quality, and Related Federal Programs 2.3 EPA Construction Permit Coverage and Operational Clocks 2.4 Industrial MSGP and Municipal MS4 Programs 2.5 Regulatory Compliance, Enforcement Mechanisms, and Penalties
3 Chapter 3: Soil Mechanics, Erosion Processes, and Climatic Factors
3.1 Soil Formation, Horizons, and Geomorphology 3.2 Soil Texture, Mechanics, and Revegetation 3.3 Splash, Sheet, Rill, Gully, Channel Erosion, and Slope Movement 3.4 Wind Erosion, Sediment Transport, Climatic Erosivity, and Resource Impacts
4 Chapter 4: Hydrology, Runoff Characteristics, and Drainage Principles
4.1 The Hydrologic Cycle, Watershed Drainage Planning, and Precipitation 4.2 Hydrologic Soil Groups, Disturbed Profiles, and Time Parameters 4.3 Hydrograph Characteristics, Curve Numbers, and Runoff Estimation Equations
5 Chapter 5: Inspection Fundamentals, Duties, and Field Procedures
5.1 Inspector Roles, Scope of Authority, and Core Professional Skills 5.2 Pre-Inspection Document Review and Inspector Support Equipment 5.3 Systematic Field Inspection Sequence, Post-Inspection Meetings, and Follow-Through
6 Chapter 6: Inspection Elements for Active Construction Sites
6.1 Pre-Construction Meetings, Entrance Posting, and On-Site Document Inspections 6.2 Inspecting Active Construction Controls and Diagnosing BMP Failure Modes 6.3 Final Stabilization Verification, Final Inspections, and Notice of Termination
7 Chapter 7: Stormwater Monitoring, Field Sampling, and Chain of Custody
7.1 Permit Monitoring Triggers and Water-Quality Indicators 7.2 Sampling Preparation and Analytical Parameters 7.3 Sampling Locations, Collection Methods, and Field Meter Calibration 7.4 Sample Preservation, Data Recording, Shipping, and Chain of Custody
8 Chapter 8: Inspection Documentation, Reporting, and Map Management
8.1 Inspection Notes and Evidence Procedures 8.2 Objective Findings and Photographic Evidence 8.3 Proper Reporting Techniques and Corrective Action Log Management 8.4 Site Drawing (Map) Management, Compliance Resolution, and Enforcement Records
9 Chapter 9: Professional Communication and Site Safety for Inspectors
9.1 Communication Protocols in Pre-Construction, Post-Inspection, and O&M Meetings 9.2 Dealing with Difficult People, Problematic Sites, and Unpleasant Findings 9.3 Site Hazard Recognition: Physical, Biological, Trenching, and Confined Spaces 9.4 Hazardous Substances, Safety Data Sheets (SDS), Spill Response, and PPE
10 Chapter 10: Stormwater Plan Reading, Map Interpretation, and Site Calculations
10.1 Stormwater Plan Types, Credentials, and Authority 10.2 SWPPP Components and Permit Notifications 10.3 Civil Plan Sets, Legends, Phased Sequencing, and Living Site Maps 10.4 Topography, Contour Lines, Slope Calculations, and Plan Amendments
11 Chapter 11: BMP Framework, Site Planning, and Erosion Control Practices
11.1 Six Functional BMP Categories, Preservation of Vegetation, Phasing, and Tree Protection 11.2 Seeding and Sod Establishment 11.3 Hydroseeding and Hydromulching Inspection 11.4 Mulch and Rolled Erosion-Control Products 11.5 Tackifiers, Soil Binders, Roughening, and Temporary Cover
12 Chapter 12: Perimeter, Linear, and In-Water Sediment Control Practices
12.1 Perimeter & Sheet-Flow Sediment Barriers: Silt Fence, Fiber Rolls, Straw Bales, and Filter Dikes 12.2 Access & Roadside Sediment/Runoff Controls: Stabilized Entrances, Cut-Back Curbs, and Ditch Checks 12.3 In-Water & Dewatering Controls: Temporary Stream Crossings, Turbidity Curtains, and Sediment Bags
13 Chapter 13: Sediment Basins, Traps, and Runoff Conveyance Controls
13.1 Sediment Basins and Traps 13.2 Porous Baffles and Surface Skimmers 13.3 Runoff Conveyances: Diversions, Swales, Pipe Slope Drains, and Rock Check Dams 13.4 Riprap and Gabion Inspection 13.5 Retaining Walls, Outlet Protection, and Wet Ponds
14 Chapter 14: Storm Drain Inlet Protection and Good Housekeeping BMPs
14.1 Storm Drain Inlet Protection: At-Grade, Curb, Block & Gravel, Excavated, Fabric Drop, Gravel Bag, Stone Collar, and Pre-Manufactured 14.2 Good Housekeeping Part 1: Concrete Washout, Equipment Maintenance, Materials Management, and Secondary Containment 14.3 Good Housekeeping Part 2: Stockpiles, Dust Control, Wind Fence, Street Cleaning, Sanitary Waste, and Trash
15 Chapter 15: Post-Construction Stormwater Management BMPs
15.1 Vegetative & Structural Dispersion BMPs: Final Ground Cover, Headwalls, Level Spreaders, Filter Strips, and Riparian Buffers 15.2 Permeable Surfaces and Construction Protection 15.3 Infiltration, Bioretention, and Media Filters 15.4 Detention, Retention & Proprietary BMPs: Dry/Wet Basins, Wetlands, Inline Storage, Catch Basin Inserts, Vaults, and Manufactured Devices
3.4 Wind Erosion, Sediment Transport, Climatic Erosivity, and Resource Impacts
Key Takeaways Explain This Topic AI
Wind erosion transports soil particles through three modes: saltation (0.1 to 0.5 mm grains bouncing < 1 m high, accounting for 50% to 80% of total transport), surface creep (0.5 to 1.0+ mm coarse grains rolling along the surface, 5% to 25%), and suspension (< 0.1 mm fine dust carried miles offsite, 3% to 40%).
In the Revised Universal Soil Loss Equation (A = R x K x LS x C x P), the cover-management factor (C) gives inspectors and site managers the greatest practical leverage, reducing soil loss by 95% to 99% when bare soil (C = 1.0) is protected with mulch, blankets, or vegetation (C < 0.05).
NRCS 24-hour design storm distributions divide the U.S. into Type I and IA (Pacific maritime wet winters with long, moderate-to-low intensity storms), Type II (most of the continental U.S. with intense convective summer thunderstorms), and Type III (Gulf and Atlantic coasts subject to tropical storms and hurricanes).
Offsite sedimentation degrades receiving waters physically, biologically, and chemically by increasing turbidity, blocking photosynthesis, smothering benthic macroinvertebrates and fish spawning gravel (redds), abrading gills, reducing flood capacity, and carrying clay-adsorbed phosphorus, heavy metals, and hydrocarbons.
Last updated: October 2026
Isohyetal maps and climate interpretation
An isohyet joins locations with equal precipitation depth for a stated storm or averaging period. Read the legend, units, date, and period before interpreting a contour: annual-average inches and a 24-hour design-storm depth answer different questions. A drainage area between the four-inch and five-inch isohyets may be subdivided into bands and assigned representative depths to calculate an area-weighted basin average. For example, 40 acres assigned four inches and 60 acres assigned five inches have an average depth of (40 × 4 + 60 × 5) ÷ 100 = 4.6 inches. This interpolation is an explicit teaching example, not a replacement for the design authority’s rainfall data.
The R rainfall-runoff erosivity factor represents rainfall energy and intensity effects used in erosion prediction. It is not the annual rain depth and is not a soil erodibility measurement. Two regions with similar annual totals can differ substantially in erosivity if one receives frequent gentle rain and the other intense convective storms. Seasonal construction scheduling can reduce exposure to high-erosivity periods, but a predicted dry season does not excuse installed controls or permit inspections.
In cold regions, distinguish snow accumulation from snowmelt discharge. Frozen or saturated soils may admit little infiltration when melt begins, and rain on snow can generate rapid runoff. Inspect access safety, functioning outlets, ice blockage, and the permit’s specific thaw and snowmelt provisions. Record actual weather and rainfall sources representative of the site; a regional map cannot prove that a particular site did or did not meet an inspection trigger.
Wind (Aeolian) Erosion and the Three Modes of Particle Transport
Under SAOP 2 Test Objectives 5 and 7 , inspectors must evaluate wind erosion hazards on flat, exposed grading pads, arid and semi-arid projects, coastal sand zones, and unstabilized soil stockpiles. Wind erosion initiates when wind velocity near the ground exceeds the threshold friction velocity (typically 12 to 15 mph 12\text{ to }15\text{ mph} 12 to 15 mph measured at 1 foot 1\text{ foot} 1 foot above smooth, dry, bare soil). Once threshold shear is exceeded, wind transports soil via three distinct physical modes:
Saltation ( 50 % to 80 % 50\%\text{ to }80\% 50% to 80% of total wind transport — The Dominant Mechanism):
Moves medium-sized particles 0.1 to 0.5 mm 0.1\text{ to }0.5\text{ mm} 0.1 to 0.5 mm in diameter (fine to medium sand and silt-sized aggregates).
Aerodynamic lift plucks these grains into the airstream, where they bounce along the surface in short, ballistic trajectories less than 1 meter 1\text{ meter} 1 meter ( 3 feet 3\text{ feet} 3 feet ) high (with the majority of mass moving within 12 inches 12\text{ inches} 12 inches of the ground).
When saltating grains slam back into the soil surface at shallow impact angles, they act as abrasive projectiles—shattering dry soil clods, pushing heavier grains forward as surface creep, and splashing microscopic silt and clay into suspension. This self-multiplying chain reaction downwind across a long, unsheltered grading pad is called the avalanching effect .
Surface Creep ( 5 % to 25 % 5\%\text{ to }25\% 5% to 25% of total wind transport):
Moves coarse sand and fine gravel particles 0.5 to 1.0 mm 0.5\text{ to }1.0\text{ mm} 0.5 to 1.0 mm (up to 2.0 mm 2.0\text{ mm} 2.0 mm ) in diameter .
Too heavy to be lifted into the airstream by wind drag alone, these coarse grains roll and slide slowly along the ground surface as they are bombarded by saltating grains, accumulating in drifts along fence lines, curbs, and haul roads.
Suspension ( 3 % to 40 % 3\%\text{ to }40\% 3% to 40% of total wind transport):
Moves fine silt and clay particles < 0.1 mm < 0.1\text{ mm} < 0.1 mm ( 100 μ m 100\text{ }\mu\text{m} 100 μ m ) in diameter , including regulated inhalable fugitive dust ( PM 10 \text{PM}_{10} PM 10 , ≤ 10 μ m \le 10\text{ }\mu\text{m} ≤ 10 μ m ) and fine respirable particulates ( PM 2.5 \text{PM}_{2.5} PM 2.5 , ≤ 2.5 μ m \le 2.5\text{ }\mu\text{m} ≤ 2.5 μ m ).
Once kicked into the air by saltating sand impacts, upward atmospheric turbulence exceeds their tiny gravitational settling velocity, lifting them high into the atmosphere and carrying them miles offsite as visible dust plumes that violate air quality permits and create highway visibility hazards.
Transport Mode Particle Diameter Range Share of Total Wind Transport Trajectory & Transport Distance Hydraulic (Fluvial) Stream Analog Primary Field Control Strategy
Surface Creep 0.5 to 1.0 mm 0.5\text{ to }1.0\text{ mm} 0.5 to 1.0 mm (up to 2.0 mm 2.0\text{ mm} 2.0 mm ) 5 % to 25 % 5\%\text{ to }25\% 5% to 25% Rolls and slides along ground surface; deposits locally at barriers Bedload contact load (coarse gravel/sand rolling along streambed) Surface roughening, wind fences, perimeter barriers
Saltation 0.1 to 0.5 mm 0.1\text{ to }0.5\text{ mm} 0.1 to 0.5 mm 50 % to 80 % 50\%\text{ to }80\% 50% to 80% (Dominant) Short hopping arcs < 1 m < 1\text{ m} < 1 m ( 3 ft 3\text{ ft} 3 ft ) high; drives avalanching Bedload saltation (sand hopping along channel invert) Stop saltation via mulch, tackifiers, water trucks, perpendicular ridges, windbreaks
Suspension < 0.1 mm < 0.1\text{ mm} < 0.1 mm (includes PM 10 \text{PM}_{10} PM 10 & PM 2.5 \text{PM}_{2.5} PM 2.5 ) 3 % to 40 % 3\%\text{ to }40\% 3% to 40% Lifted high into atmosphere; travels miles offsite as fugitive dust Suspended load and wash load (fine silt/clay held in water column) Prevent saltation bombardment; apply polymeric soil binders, crusting tackifiers, or vegetative cover
Tip
Stopping Saltation Stops All Three Wind Modes: Because saltating grains ( 0.1 to 0.5 mm 0.1\text{ to }0.5\text{ mm} 0.1 to 0.5 mm ) provide the impact energy that pushes surface creep and blasts suspension dust into the air, wind-erosion BMPs focus on halting saltation. Applying tackifiers/soil binders, maintaining surface moisture with water trucks, creating ridges perpendicular to the prevailing wind (surface roughening), and installing wind fences (which create a sheltered downwind zone extending 7 to 10 times 7\text{ to }10\text{ times} 7 to 10 times the fence height H H H ) keep wind shear below the threshold velocity at the soil surface.
Predicting Soil Loss: RUSLE, MUSLE, and WEQ
Stormwater designers and CESSWI inspectors use empirical prediction models to evaluate relative erosion risk and verify whether proposed BMPs reduce soil loss to acceptable levels.
The Revised Universal Soil Loss Equation (RUSLE)
Developed by the USDA Agricultural Research Service and NRCS, RUSLE predicts long-term average annual soil detachment by sheet and rill erosion (it does not calculate gully erosion, in-stream channel scour, or mass wasting): A = R × K × L S × C × P A = R \times K \times LS \times C \times P A = R × K × L S × C × P
A A A = Average Annual Soil Loss ( tons/acre/year \text{tons/acre/year} tons/acre/year ).
R R R = Rainfall-Runoff Erosivity Factor: Measures the climatic driving force of local precipitation, calculated as the annual summation of individual storm total kinetic energy ( E E E ) multiplied by the maximum 30-minute rainfall intensity ( I 30 I_{30} I 30 ), known as the E I 30 EI_{30} E I 30 index .
K K K = Soil Erodibility Factor: Measures the intrinsic susceptibility of a soil horizon to detachment and transport per unit of R R R (highest for silt and very fine sand at 0.40 to 0.65 0.40\text{ to }0.65 0.40 to 0.65 ; lowest for coarse sand and high-clay/high-organic soils at 0.02 to 0.20 0.02\text{ to }0.20 0.02 to 0.20 ).
L S LS L S = Slope Length ( L L L ) and Slope Steepness ( S S S ) Topographic Factor: Dimensionless ratio comparing soil loss from a given slope length and gradient to a standard unit plot ( 72.6 ft 72.6\text{ ft} 72.6 ft long at 9 % 9\% 9% slope). Slope length ( L L L ) is measured from the point where overland flow originates to the point where flow concentrates into a channel or deposition begins. Crucial exam concept: Increasing slope steepness ( S S S ) increases soil loss much more rapidly (exponentially) than an equivalent proportional increase in slope length ( L L L ). Installing fiber rolls (wattles) or diversions mid-slope reduces L L L ; flattening cut/fill grades reduces S S S .
C C C = Cover-Management Factor: Dimensionless ratio of soil loss from a protected surface compared to bare, untended soil ( C = 1.0 C = 1.0 C = 1.0 ). This is the single most powerful lever on a construction site: whereas R R R and K K K are fixed by location and native geology, applying straw mulch, hydromulch, or RECPs (or establishing dense turf) immediately drops C C C from 1.0 1.0 1.0 down to 0.01 to 0.05 0.01\text{ to }0.05 0.01 to 0.05 , cutting sheet and rill erosion by 95 % to 99 % 95\%\text{ to }99\% 95% to 99% .
P P P = Support Practice Factor: Dimensionless ratio accounting for mechanical surface roughness and directional orientation—such as contour tracking (driving a tracked bulldozer up and down the slope so the horizontal track cleat impressions run parallel to the contour, P ≈ 0.8 to 0.9 P \approx 0.8\text{ to }0.9 P ≈ 0.8 to 0.9 ), terracing, or contour furrowing. Conversely, running wheeled equipment up and down a slope creates vertical ruts that channelize runoff ( P > 1.0 P > 1.0 P > 1.0 ).
MUSLE and WEQ
Modified Universal Soil Loss Equation (MUSLE): Replaces the annual rainfall erosivity factor ( R R R ) with a single-storm runoff energy factor based on total storm runoff volume ( Q v Q_v Q v ) and peak runoff rate ( q p q_p q p ) ( 11.8 ( Q v × q p ) 0.56 11.8 (Q_v \times q_p)^{0.56} 11.8 ( Q v × q p ) 0.56 ). Unlike RUSLE, MUSLE directly predicts single-storm sediment yield delivered to a basin or outfall.
Wind Erosion Equation (WEQ): Expressed as E = f ( I , K , C , L , V ) E = f(I, K, C, L, V) E = f ( I , K , C , L , V ) , where annual wind soil loss ( E E E ) is a function of the Soil Erodibility Index ( I I I , governed by the percentage of non-erodible soil clods > 0.84 mm > 0.84\text{ mm} > 0.84 mm ), Ridge Roughness ( K K K ), Climatic Factor ( C C C , proportional to the cube of wind velocity divided by the square of effective surface moisture), Unsheltered Distance ( L L L along the prevailing wind vector), and Vegetative Residue Cover ( V V V ).
Site Climatic Conditions, Rainfall Characteristics, and NRCS Storm Types (SAOP 3)
Under SAOP 3 (Site Climatic Conditions and Rainfall Amounts) , an inspector must evaluate four precipitation characteristics— intensity ( in/hr \text{in/hr} in/hr ), duration ( hours \text{hours} hours ), frequency / return period (e.g., 2-year, 10-year, or 25-year 24-hour storm), and seasonal distribution —to anticipate site vulnerability.
To model runoff and size stormwater BMPs across diverse U.S. climates, the USDA Natural Resources Conservation Service (NRCS) defines four 24-hour synthetic rainfall distributions:
NRCS Storm Distribution Geographic Region in the United States Dominant Storm Meteorology & Seasonal Pattern Peak Intensity Profile & Field Inspection Implications
Type IA Pacific Maritime Northwest (coastal Washington, coastal Oregon, northern California) Cool, wet winters dominated by long-duration, low-intensity Pacific frontal systems Lowest peak intensity curve; prolonged soil saturation, high water tables, seesaw basin fullness, and rotational slope slumps
Type I Coastal/central/southern California, Alaska, Hawaii, and inland Pacific Northwest wet-winter zones Mediterranean or maritime wet winters and extended dry summers Moderate peak intensity; requires strict pre-winter stabilization before autumn rains arrive
Type II Most of the continental United States (Intermountain West, Midwest, Great Plains, Interior South, Northeast interior) Intense, short-duration convective summer thunderstorms Steepest dimensionless peak intensity curve ; violent 30-to-60-minute cloudbursts generate extreme splash detachment ( E I 30 EI_{30} E I 30 ) and flash rill/gully scour
Type III Gulf of Mexico Coast and Atlantic Coastal Seaboard (TX, LA, MS, AL, FL, and Atlantic coastal plain) Tropical storms, hurricanes , and coastal Nor'easters Combines massive 24-hour rainfall totals ( 6 to 15 + inches 6\text{ to }15+\text{ inches} 6 to 15 + inches ) with high peak intensities; overwhelms hydraulic conveyance and requires emergency overflow spillways
Arid/Semi-Arid Climates, Freeze-Thaw Cycles, and Weather Monitoring
Arid and Semi-Arid Regions ( 0 to 20 inches 0\text{ to }20\text{ inches} 0 to 20 inches annual rainfall): Characterized by thin, alkaline/sodic soils, protective biological soil crusts, high wind erosion potential, and long droughts interrupted by violent convective flash floods (monsoons). Because low moisture prevents rapid seed establishment without irrigation, inspectors prioritize phased disturbance limitation, non-vegetative surface armor (gravel/rock mulch, soil binders, crimped straw), and perimeter runoff diversions.
Freeze-Thaw Cycles and Rain-on-Snow Events: In cold climates, repeated freezing and thawing forms needle ice ( frost heaving ) that detaches surface soil aggregates and leaves the upper 2 to 4 inches 2\text{ to }4\text{ inches} 2 to 4 inches of a cut slope saturated and cohesionless atop an impermeable frozen subsoil layer. When spring rain falls on melting snowpack ( rain-on-snow ), virtually 100 % 100\% 100% of the water becomes runoff over thawed, soupy surface soil, triggering severe sheet, rill, and translational slope failures.
Inspector Weather Tracking: Inspectors check National Oceanic and Atmospheric Administration (NOAA) / National Weather Service (NWS) Quantitative Precipitation Forecasts 48 to 72 hours 48\text{ to }72\text{ hours} 48 to 72 hours before predicted storms to verify pre-storm BMP readiness, and read calibrated on-site rain gauges (or representative NOAA stations within 1 mile 1\text{ mile} 1 mile ) to verify when permit inspection thresholds (such as 0.25 inches 0.25\text{ inches} 0.25 inches under the EPA CGP) are triggered.
Resource and Community Impacts of Offsite Erosion and Sedimentation
Sediment is the largest pollutant by volume entering surface waters in the United States, and construction sites contribute a disproportionate share when controls fail. Offsite sedimentation causes three interconnected categories of harm:
Physical and Hydraulic Infrastructure Impacts: Coarse and medium sediment settles in roadside ditches, storm sewer pipes, catch basins, and navigation channels, reducing hydraulic conveyance capacity and increasing localized upstream flooding. Fine sediment accumulates in downstream lakes, reservoirs, and post-construction stormwater basins, permanently destroying flood storage volume and requiring costly dredging.
Biological and Ecological Impacts:
Turbidity and Light Attenuation: Suspended silt and clay increase turbidity (measured in Nephelometric Turbidity Units, NTU) and Total Suspended Solids (TSS, mg/L \text{mg/L} mg/L ) , blocking sunlight penetration into the water column, halting photosynthesis in submerged aquatic vegetation (SAV) and phytoplankton, lowering dissolved oxygen, and raising water temperatures (dark turbid water absorbs more solar radiation).
Gill Abrasion and Feeding Disruption: Angular suspended mineral grains clog and abrade the delicate gill filaments of fish and aquatic larvae, while high turbidity blinds sight-feeding game fish.
Benthic Smothering and Redd Siltation: When suspended silt settles onto cobble and gravel streambeds ( substrate embeddedness ), it fills interstitial pore spaces, smothering benthic macroinvertebrates (mayfly, stonefly, and caddisfly larvae at the base of the aquatic food web) and suffocating fish eggs and fry inside salmonid and trout spawning beds ( redds ) by cutting off oxygenated intragravel water flow.
Chemical and Pollutant-Transport Impacts ("Piggyback" Pollutants): Because clay micelles and fine organic silt possess immense specific surface area and negative electrical surface charges, they strongly adsorb chemical pollutants —most notably phosphorus (the primary limiting nutrient driving freshwater cultural eutrophication, harmful algal blooms, and hypoxic dead zones), heavy metals (lead, zinc, copper, cadmium), pesticides, and petroleum hydrocarbons. Retaining fine sediment on site is therefore simultaneously a chemical water-quality control.