CPESC key terms

Uniform removal of a thin layer of soil across a slope by raindrop impact and shallow overland flow. It is often hard to see because no channels form, yet it delivers sediment and nutrients downslope.

Concentrated overland flow cutting small, shallow channels that are typically only a few inches deep and can be crossed by ordinary tillage. Rills mark the transition between sheet erosion and gully erosion.

Deep, well-defined channels cut by concentrated flow that cannot be smoothed out by normal tillage. Gullies enlarge headward, deliver large sediment loads, and usually need structural treatment rather than surface cover alone.

A model that estimates long-term average annual soil loss from sheet and rill erosion as the product of rainfall, soil erodibility, slope length and steepness, cover management, and supporting practice factors.

A RUSLE factor expressing how much surface cover and management reduce soil loss compared with bare, continuously tilled ground. Values near zero mean strong protection; values near one mean little protection.

A manufactured mat of straw, wood, coconut, or synthetic fiber laid on a prepared seedbed to shield soil from raindrop impact, slow runoff, and hold moisture. Type is chosen by slope steepness and how long protection is needed.

Graded rock placed on erodible surfaces, channels, or outlets to resist flow forces. Good design depends on rock size and gradation, a filter layer or geotextile beneath, and a properly keyed toe.

A temporary perimeter barrier of geotextile on posts that ponds runoff and lets sediment settle out. It works only for sheet flow, needs a level trench with buried fabric, and must be checked after every rain.

A temporary excavated or embankment pool that holds sediment-laden runoff long enough for particles to settle before release. It requires designed storage volume, a controlled outlet, and regular sediment removal.

Releasing or pumping standing water out of an excavation, basin, or work area in a controlled manner. Discharge must pass through suitable treatment and go to a stable, permitted outlet.

A small structure of rock, logs, or manufactured material placed across a swale or channel to slow flow, reduce erosion, and encourage sediment deposition. It must be keyed into the banks with a stable low center.

A pad of coarse aggregate, often over geotextile, placed where vehicles leave a site so soil is knocked off tires instead of tracked onto public roads. It needs regular topdressing and cleaning.

A temporary barrier or filter around a storm drain inlet that keeps sediment on site while still allowing water to drain. It must not cause flooding and is removed once the contributing area is stabilized.

A chemical that causes fine suspended soil particles to clump into larger aggregates that settle faster. It must be selected, dosed, and applied so no harmful residual leaves the site.

A measure of how much suspended material scatters light in a water sample, reported in nephelometric turbidity units. It serves as an indicator of sediment pollution and is sometimes used as a discharge benchmark.

The time required for runoff from the most hydraulically remote point of a drainage area to reach the outlet. It sets the storm duration used when computing peak discharge.

A simple peak discharge equation, Q equals CiA, multiplying a runoff coefficient, rainfall intensity, and drainage area. It applies mainly to small catchments where one intensity can reasonably be assumed.

An empirical index from 0 to 100 that estimates how much rainfall becomes direct runoff, based on land cover, treatment, and hydrologic soil group. Higher numbers mean more runoff.

A rainfall event of chosen depth, intensity, and duration with an associated return period, used to size drainage and control measures. Which storm to use is normally fixed by local or state rules.

A formula for average velocity in open channels and pipes combining hydraulic radius, bed slope, and a roughness coefficient. It is widely used to check capacity and shear stress in swales, ditches, and outlets.

The maximum average annual soil loss that still allows long-term soil productivity to be maintained. It is expressed in tons per acre per year and differs by soil type.

One of four classes, A through D, assigned to soils based on their minimum infiltration rate when wet. They range from well-drained sands to clays that generate the most runoff.

The relative proportions of sand, silt, and clay particles in a soil. Texture strongly governs infiltration, erodibility, and how well the soil holds water and nutrients.

The ability of soil particles to stay bound together in clumps when wetted or struck by rain. Stable aggregates resist raindrop detachment, so well-aggregated topsoil erodes much less.

Soil whose clay particles separate and go into suspension in water, causing rapid internal erosion, tunnel formation, and difficult stabilization. It is identified by tests such as the pinhole or crumb test.

The National Pollutant Discharge Elimination System, the Clean Water Act program requiring permits for point source discharges of pollutants to waters of the United States, including many construction stormwater discharges.

An NPDES general permit issued by EPA or an authorized state covering stormwater discharges from construction sites disturbing one acre or more. It sets effluent limits, monitoring duties, and plan requirements.

A form filed with the permitting authority to obtain coverage under a general permit. It identifies the operator, site, and planned controls and must be submitted before earth-disturbing work starts.

The maximum pollutant load a water body can receive and still meet water quality standards, divided among sources including stormwater. TMDLs can trigger stricter local requirements and monitoring.

Publicly owned conveyances that collect and carry stormwater to waters of the United States. MS4 operators hold permits and often impose extra requirements on construction sites inside their boundaries.

A site-specific plan describing erosion and sediment controls, pollution prevention practices, inspection and maintenance procedures, and responsible parties for a construction project. It must be kept current and followed as written.

A schedule, practice, or structural control used to prevent or reduce pollutants in stormwater. Examples include silt fence, surface stabilization, and good housekeeping; selection depends on site conditions and permit requirements.

The portion of a site where soil or existing vegetation is removed or altered by construction activity. It drives permit applicability, sizing of controls, and stabilization deadlines.

A contained area or prefabricated unit where concrete trucks and tools are washed so highly alkaline, high-solids water does not reach storm drains or soil. Solids are removed and the unit is kept serviceable.

A repair, replacement, or modification that brings a failing or inadequate control back into compliance. Findings should be documented, assigned to a responsible person, and closed within a stated timeframe.

A scheduled site walk confirming that controls are installed, working, and maintained as specified, with extra checks after rain. Results are logged with location, condition, and needed follow-up.

Keeping permits, plans, inspection reports, and monitoring results for the period required by the permit or regulation. Records should be legible, dated, organized, and available to regulators on request.

A situation where a professional's financial, personal, or other interest could impair, or appear to impair, objective judgment on a project. It must be disclosed and then avoided or formally managed.

A stamp or mark a licensed professional applies to show that work was prepared or reviewed under their responsible charge. It may be used only on work within their competence and legal authority.