United States Department of Agriculture 600-CPS-1

NRCS, NHCP

August 2023

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 

TERRACE 

CODE 600 

(ft)

DEFINITION 

An earth embankment or a combination ridge and channel, constructed across the field slope. 

PURPOSE 

This practice is used to accomplish one or more of the following purposes: 

• Reduce erosion and trap sediment. 

• Manage runoff. 

• Soil moisture conservation. 

CONDITIONS WHERE PRACTICE APPLIES 

This practice applies only where the soils and topography are such that terraces can be constructed, a

suitable outlet can be provided, and where one or more of the following conditions exist: 

• Soil erosion caused by water and excessive slope length is a concern. 

• Excess runoff is a concern. 

• Water conservation is needed. 

CRITERIA 

General Criteria Applicable to All Purposes 

Plan, design, and construct the terrace to meet all Federal, State, Tribal, and local regulations. 

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

when locating terraces. Utilize field investigations and soil surveys to identify potential problems areas. 

Alignment 

Terraces must follow the contour of the land. Limit deviations from the contour and allow only when

necessary to obtain good alignment. To accommodate farm machinery and farming operations, design

cropland terraces with long gentle curves, where feasible. When multiple terraces are used in a field,

design the terraces to be as parallel to one another as practicable. Refer to NRCS Conservation Practice

Standard (CPS) Contour Farming (Code 330) for guidance on planning farming operations. 

Spacing 

Space terraces at intervals across the slope to achieve the intended purpose. The maximum spacing of

terraces for erosion control is that necessary to achieve the soil loss tolerance (T) or other soil loss criteria

that is documented in the Field Office Technical Guide. Maximum spacing for erosion control based on soil

loss tolerance may be increased by as much as 10 percent to provide better location and alignment to

accommodate farm machinery or to reach a satisfactory outlet. 
The methods to determine terrace spacing include the current NRCS accepted erosion prediction

technology, the vertical interval equation, or State-developed methods that address unique soil, cropping,

or other farming practices that affect terrace spacing. Refer to the current NRCS accepted erosion

prediction technology to determine soil loss. The slope length used when checking soil loss for a proposed

terrace spacing is the distance from the terrace ridge to the next lower terrace channel measured along

the natural flow direction. 

Include both the terrace system with design slopes and cultural practices such as residue management

when determining soil loss. Refer to the NRCS National Engineering Handbook (NEH) (Title 210), Part

650, Chapter 8, “Terraces” for use of the vertical interval equation. 

Capacity 

At a minimum design terraces to have enough capacity to control runoff from a 10-year-frequency, 24-hour

storm without overtopping. For terrace systems designed to control excess runoff or to function with other

structures, choose a larger design storm that is appropriate to the risk associated with the installation. 

For terraces with underground outlets, the capacity to contain the design storm can be a combination of

storage and outflow through the underground outlet. For terraces that store runoff (storage or level

terraces), increase the storage capacity by the estimated 10-year sediment accumulation, unless the

operation and maintenance plan specifically addresses periodic removal of sediment. 

For terraces with open outlets, base the terrace channel size on the capacity using the densest and

longest vegetation. Base the capacity of the channel on a bare earth channel for cropped fields, or in the

case of a permanently vegetated channel, the appropriate vegetation. For bare earth channels, use a

Manning’s n value of 0.035 or greater to calculate capacity. For permanently vegetated channels, refer to

NRCS CPS Grassed Waterway (Code 412) for design criteria to determine capacity and NRCS CPS

Critical Area Planting (Code 342) for seeding criteria. 

Terrace cross section 

Proportion the terrace cross section to fit land slope, crops grown, and farm machinery used. Avoid use of

terrace cross sections that results in disturbance of the majority of the soil in the spacing between

terraces. Add ridge height, if necessary, to provide for settlement, channel sediment deposits, ridge

erosion, the effect of normal tillage operations, or safety. At the design elevation, the ridge must have a

minimum width of 3 feet. Design all farmable terrace slopes no steeper than 5 horizontal to 1 vertical to

allow safe operation of farming equipment. For nonfarmable terrace slopes, the steepest slopes allowable

are 2 horizontal to 1 vertical unless an analysis of site specific soil conditions indicate that steeper slopes

will be stable. 

Channel grade 

Design the terrace channel to be stable with nonerosive velocities but with sufficient grade to prevent

prolonged flooding that would damage crops or delay farming activities. For cultivated terraces, base the

channel stability on a bare earth condition using a maximum Manning’s n value of 0.035. For permanently

vegetated channels, base the channel stability on the appropriate vegetation. Refer to NRCS CPS

Grassed Waterway (Code 412) and 210-NEH-650, Chapter 7, “Grassed Waterways” for design criteria

and procedures to determine stability for both bare and vegetated conditions. In the upper reaches of a

channel, grades may be increased to improve alignment. For terraces with an underground outlet, channel

grades can be steeper within the impoundment area. 

Level terraces 

The volume of water stored in level terraces is proportional to the length. To reduce the potential risk from

failure, limit the length of level terraces to 3,500 feet unless the channel is blocked at intervals not

exceeding 3,500 feet. Level terraces can have either full- or partial-end closures or be open-ended. If a

partial-end closure is used, areas downstream from the end closure must be protected from damage by

flow that will exit from the closure before the design storm is reached. 

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Outlets 

All terraces must have adequate outlets. The outlet must convey runoff water to a point where it will not

cause damage. Combinations of different outlet types may be used on the same terrace system to

optimize water conservation, improve water quality, accommodate farming operations, or provide for

economical installation. The capacity of any surface outlet must be large enough so the terrace can

properly discharge at the design flow. 

Vegetated outlets are suitable for gradient or open-end level terraces. Naturally vegetated drainage ways

may be used as vegetated outlets. The capacity of the vegetated outlet must be large enough so that the

water surface in the outlet is at or below the water surface in the terrace at the design flow. If a grassed

waterway is to be constructed as an outlet, use NRCS CPS Grassed Waterway (Code 412). Install and

stabilize grassed waterways prior to construction of the terrace so the terrace will have a stable outlet

when it is constructed. 

Underground outlets are suitable for use on all terrace types. The outlet consists of an intake and an

underground conduit. If underground outlets are to be constructed, use NRCS CPS Underground Outlet

(Code 620). Design the outlet so the water storage time does not exceed the inundation tolerance of the

planned crop. If sediment retention is a primary design goal, adjust the release rate according to sediment

particle size. Locate the intake structure for the underground outlet to accommodate farming operations

and to allow for sediment accumulation. 

Soil infiltration may be used as the outlet for level terraces. Soil infiltration rates under average rainfall

conditions must permit infiltration of the design storm from the terrace channel within the inundation

tolerance of the planned crops. 

Vegetation 

Stabilize all areas planned for vegetation as soon as possible after construction. Refer to NRCS CPS

Critical Area Planting (Code 342) or State planting guide for seeding criteria, and as needed, use the

criteria in NRCS CPS Mulching (Code 484). Establish temporary cover on disturbed areas such as

channels and borrow areas that are not planned for permanent vegetation, but will not have a crop planted

within 90 days. 

Additional Criteria for Managing Runoff and Soil Moisture Conservation 

For terraces installed to retain runoff for moisture conservation, perform a water budget analysis to

determine the volume of water that must be collected to meet the requirements of the water budget. 

For terraces installed to manage runoff to reduce flooding or ponding, size the detention volume of all

terraces in the system such that the necessary downstream flood protection is achieved. 

As a minimum, the terrace must still meet the design storm runoff volume and sediment volume

requirements in the Capacity section above. 

CONSIDERATIONS 

Consider climate change impact on determining channel’s capacity. 

Outlets from terraces 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. Terraces should be

installed as part of a conservation system that addresses issues such as nutrient and pest management,

residue management, and filter areas. 

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Consider farm equipment size when determining layout. This may include making curves long and gentle

and spacing terraces so the operator can make an even number of trips between terraces in order to end

up on the same side of the field they started. 

Where necessary to restore or maintain productivity, consider temporarily stockpiling the topsoil adjacent

to the site and spreading over the disturbed area after construction is complete. 

When revegetation is needed, consider using species or diverse mixes that are native or adapted to the

site and have multiple benefits. In addition, where appropriate, consider a diverse mixture of forbs and

wildflowers to support pollinator and other wildlife habitat. If USDA certified-organic and or transitioning-toorganic operations, all materials need to comply with the USDA National Organic Program (NOP)

Standards, including all seeds, planting stock, fertilizers, and other production inputs. 

Terrace ridges and cut slopes can introduce steep and potentially hazardous slopes into a crop field.

Where slopes will be farmed, make sure they can be safely negotiated with the operator’s equipment.

Where steep slopes are unavoidable make sure the operator is aware of the location and potential danger

of the slopes. 

Steep-sided terraces that are in permanent vegetation can provide significant areas of habitat for wildlife.

Planting native species can provide food and cover for wildlife. 

Hillside seeps in a crop field can cause cropping problems. Consider aligning terraces and/or installing

subsurface drainage to intercept and correct seepage problems. Install the drainage prior to terrace

construction by using NRCS CPS Subsurface Drain (Code 606). 

Intakes for underground outlets can be easily damaged during cultivation, planting, and harvesting

operations. Using brightly colored inlets, barriers around the inlet, or otherwise clearly marking the inlet

will help prevent damage. 

PLANS AND SPECIFICATIONS 

Prepare plans and specifications that describe the requirements for applying the practice according to this

standard. As a minimum the plans and specifications must include— 

• A plan view of the layout of the terrace system. 

• Typical cross sections of the terrace(s). 

• Profile(s) or planned grade of the terrace(s). 

• Details of the outlet system. 

• If underground outlets are used, details of the inlet and profile(s) of the underground outlet. 

• Seeding requirements, if needed. 

• Site-specific construction specifications that describe in writing the installation of the terrace

system. 

OPERATION AND MAINTENANCE 

Prepare an operation and maintenance plan for the operator to follow for the design life of the terrace

system. The minimum requirements to be addressed in the written operation and maintenance plan are— 

• Intended orientation of the primary farming operations, usually parallel to the terrace(s). 

• Periodic inspections, especially immediately following significant runoff events. 

• Prompt repair or replacement of damaged components. 

• Maintenance of terrace ridge height, channel profile, terrace cross sections and outlet elevations. 

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

• Regular cleaning of inlets for underground outlets. Repair or replacement of inlets damaged by farm

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August 2023
equipment. Removal of sediment around inlets to ensure that the inlet remains the lowest spot in

the terrace channel. 

• Where vegetation is specified, complete seasonal mowing, control of trees and brush, reseed and

fertilize as needed. 

• Repair damages from burrowing animals. 

• Notification of hazards about steep slopes on the terrace. 

REFERENCES 

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

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

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

Chapter 7, Grassed Waterways. Washington, D.C.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=46771.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

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August 2023