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NRCS reviews and periodically updates conservation practice standards. To obtain the current 

version of this standard, contact your Natural Resources Conservation Service State office or 

visit the Field Office Technical Guide online by going to the NRCS website at 

https://www.nrcs.usda.gov/ and type FOTG in the search field. 

USDA is an equal opportunity provider, employer, and lender.

Natural Resources Conservation Service 

CONSERVATION PRACTICE STANDARD 

WATER AND SEDIMENT CONTROL BASIN 

CODE 638 

(no)

DEFINITION 

An earth embankment or a combination ridge and channel constructed across the slope of a minor

drainageway. 

PURPOSE 

This practice may be applied for one or more of the following purposes: 

• Reduce gully erosion. 

• Trap sediment. 

• Reduce and manage runoff. 

CONDITIONS WHERE PRACTICE APPLIES 

This practice applies to sites where: 

• The topography is generally irregular. 

• Gully erosion is a problem. 

• Other conservation practices typically control sheet and rill erosion. 

• Runoff and sediment damages land and works of improvement. 

• Stable outlets are available. 

Do not use this standard in place of a terrace. Use NRCS Conservation Practice Standards (CPS)

Terrace (Code 600) or CPS Diversion (Code 362) where the ridge or channel extends beyond the

detention basin or level embankment. 

CRITERIA 

General Criteria Applicable to All Purposes 

Plan, design, and construct the water and sediment control basin to meet all Federal, State, Tribal, and

local regulations. Install a water and sediment control basin as part of a conservation system that

addresses resource concerns both above and below the basin. Where land ownership or physical

conditions preclude treatment of the upper portion of a slope, a water and sediment control basin can

separate this area and permit treatment of the lower slope. 

 Avoid areas of shallow or dense bedrock and acidic or saline layers that will adversely affect plant growth

when locating control basins. Utilize field investigations and the soil survey to identify potential problems

areas. 
Location 

Locate the water and sediment control basin to reduce erosion in a drainageway. Install a basin singly or

in series as part of a system to fit site conditions. Adjust the location to— 

• Fit the topography. 

• Maximize storage. 

• Accommodate farm equipment and farming operations. 

• Avoid impacts to adjacent properties. 

When choosing the location, evaluate the extent of ponding that will occur from the basin. 

Earth Embankment 

Table 1 displays the minimum embankment top width based on fill height. Construct the embankment at

least 5 percent greater than design height to allow for settlement. Design the settled height of the

embankment no higher than 15 feet measured from natural ground at the centerline of the embankment. 

Strip the foundation surface to remove any vegetation and unsuitable material, such as crop residue or

large rocks. Scarify the surface prior to fill placement for the embankment, and if applicable, prior to

installing a foundation cutoff, with or without seepage control. 

Table 1. Minimum top width of embankment. 

Design embankment slopes no steeper than 2 horizontal to 1 vertical. The sum of the horizontal

components of the upstream and downstream slopes of the embankment must be 5 or greater. 

Design all farmable slopes no steeper than 5 horizontal to 1 vertical to allow safe operation of farming

equipment. 

Foundation cutoff and seepage control 

Portions of a basin ridge designed to impound more than a 3-foot depth of water must include foundation

cutoff and if conditions warrant, seepage control. Refer to NRCS CPS Pond (Code 378) for criteria for

foundation cutoff and seepage control. 

Capacity 

As a minimum, design the water and sediment control basin with sufficient capacity to control the runoff

from a 10-year frequency, 24-hour-duration storm using a combination of flood storage and discharge

through the outlet. Refer to NRCS Title 210, National Engineering Handbook (210-NEH), Part 650,

Chapter 8, “Terraces” for flood routing guidance. If warranted, use a larger design storm appropriate to the

risk. 

Design the water and sediment control basin to have a minimum capacity to store the anticipated 10-year

sediment accumulation. The sediment storage volume may be reduced if periodic sediment removal is

required in the operation and maintenance plan. 

Outlets 

Provide an outlet that can convey runoff water to a point where it will not cause damage. Design the outlet

as an underground outlet, a pipe drop structure, a soil infiltration area, a stable channel, or a combination

of outlet types. 

For a farmed basin, design the outlet so that the water storage time does not exceed the inundation

tolerance of the planned crops. If sediment retention is a primary design goal, adjust the release rate

Fill Height (ft) Top Width (ft)

0–5 3

5–10 6

10–15 8

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according to sediment particle size to retain sediment in the basin. Refer to 210-NEH, Section 3, Chapter

2, “Sediment Properties” for information on the settling rates of sediment particles and to CPS

Underground Outlet (Code 620) for design criteria for underground outlets. 

The basin outlet system may include an auxiliary spillway above the primary storage to handle larger

storm flows. If an auxiliary spillway is used, add freeboard to the design height of the embankment to

provide for the safe operation of the spillway. The freeboard should be at least 0.5 ft above the design flow

depth through the auxiliary spillway. If the auxiliary spillway of another basin contributes runoff to the

basin, design the basin to handle the additional runoff. Refer to CPS Pond (Code 378) for criteria to

design an auxiliary spillway. 

Vegetation 

After construction of the water and sediment control basin, vegetate all nonfarmed disturbed areas with

permanent native or noninvasive vegetation. If establishing permanent vegetation is not feasible when

construction is complete, apply temporary cover until establishment of permanent vegetation can occur. 

In nonfarmland settings, use other erosion protection, such as gravel or organic mulches, as necessary. 

Refer to NRCS CPS Critical Area Planting (Code 342) for criteria on seed selection, seedbed preparation,

fertilizing, and seeding and NRCS CPS Mulching (Code 484) for criteria on mulch selection including

erosion control blankets. 

CONSIDERATIONS 

Consider climate change impact on determining Water and Sediment Control Basin’s capacity. 

Outlets might provide a direct conduit to receiving waters for contaminated runoff from cropland. Consider

impacts on downstream source water due to erosion and sediment load and impacts on important fish and

wildlife habitats such as streams, creeks, riparian areas, groundwater, and wetlands. 

Consider providing an increased level of designed treatment for sites with high priority areas for source

water protection or are upstream of community drinking water withdrawal sites. 

Water and sediment control basins may be spaced at intervals down a slope, similar to terraces, in order

to control erosion. Refer to NRCS CPS Terrace (Code 600) for methods to determine spacing. Install

additional conservation measures in the watercourse between basins to prevent erosion as necessary. 

Where necessary to restore or maintain productivity, salvage topsoil and spread over the disturbed area

after construction is complete. Temporarily stockpile the topsoil away from the site and provide erosion

protection, as needed. 

Consider using biodegradable erosion control blankets to protect bare soil surfaces during the

establishment of vegetation. 

Enhance sediment retention within the basin with inlet and outlet selection and by increasing the length-towidth ratio of the basin. Determine sedimentation rates using the NRCS Revised Universal Soil Loss

Equation, Ver. 2 (RUSLE2), or other approved methodology. 

For cropped fields, orient the embankment and crop rows in a direction that is approximately

perpendicular to the land slope to support contour farming. The design should support farmability by

limiting short point rows or sharp curves. Consider field boundaries and row lengths when planning basin

locations and row direction. 

Underground outlets may provide a direct conduit to receiving waters for contaminated runoff. Install

underground outlets and the accompanying structures or practices as part of a conservation system that

addresses issues such as nutrient and pest management, residue management, and filter areas. 

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PLANS AND SPECIFICATIONS 

Prepare plans and specifications for water and sediment control basins that describe the requirements for

applying the practice to achieve the intended purpose. As a minimum, include: 

• A plan view of the layout of the water and sediment control basin system. 

• Typical cross sections of the basin. 

• Profile of the basin. 

• Details of the outlet system. 

• For underground outlets, details of the inlet and profile(s) of the underground outlet. 

• Seeding and mulching requirements if needed. 

• Construction specifications that describe site-specific installation requirements. 

OPERATION AND MAINTENANCE 

Prepare an operation and maintenance plan for the operator. The minimum requirements in the operation

and maintenance plan are: 

• Periodic inspections, especially immediately following significant runoff events. 

• Prompt repair or replacement of damaged components. 

• Maintenance of basin ridge height and outlet elevations. 

• Removal of sediment that has accumulated in the basin to maintain capacity and grade. 

• Regular cleaning of inlets for underground outlets. 

• Repair or replacement of inlets damaged by farm equipment. 

• Removal of sediment around inlets to ensure that the inlet remains the lowest spot in the basin. 

• Where vegetation is specified, regular mowing and control of trees and brush. 

• Schedule vegetative disturbances to avoid the peak-nesting season. 

• Notification of hazards about steep slopes on the basin or the embankment. 

REFERENCES 

USDA NRCS. 2004. Revised Universal Soil Loss Equation, Ver. 2 (RUSLE2).

http://fargo.nserl.purdue.edu/rusle2_dataweb/RUSLE2_Index.htm

USDA NRCS. 2011. National Agronomy Manual (Title 190), Part 501, Water Erosion. Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=29608.wba

USDA NRCS. 2021. National Engineering Handbook (Title 210), Part 650, Engineering Field Handbook,

Chapter 6, Structures, Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=46256.wba

USDA NRCS. 2021. National Engineering Handbook (Title 210), Part 650, Engineering Field Handbook,

Chapter 8, Terraces. Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=46257.wba

USDA NRCS. 2021. National Engineering Handbook (Title 210), Part 650, Engineering Field Handbook,

Chapter 14, Water Management (Drainage). Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=46289.wba

USDA NRCS. 1983. National Engineering Handbook (Title 210), Section 3, Chapter 2, Sediment

Properties. Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=17508.wba

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