582-CPS-1

NRCS, NHCP

September 2015

Conservation practice standards are reviewed periodically and updated if 

needed. To obtain the current version of this standard, contact your 

Natural Resources Conservation Service State office or visit the Field 

Office Technical Guide.

Natural Resources Conservation Service

CONSERVATION PRACTICE STANDARD 

OPEN CHANNEL

Code 582

(Ft.)

DEFINITION

An open channel is a natural or artificial channel in which water flows with a free surface.

PURPOSE

Construct, improve, or restore an open channel to convey water required for flood prevention, drainage, 

wildlife habitat protection or enhancement, or other authorized water management purpose.

CONDITIONS WHERE PRACTICE APPLIES

This standard applies to the construction of open channels or modifications of existing streams or ditches 

with drainage areas exceeding one (1) mi2(1.6 km2). This standard does not apply to Natural Resources 

Conservation Service (NRCS) Conservation Practice Standards (CPSs) Codes 362, Diversions; 412, 

Grassed Waterways; 388, Irrigation Field Ditches; 607, Surface Drain, Field Ditch; or 320, Irrigation 

Canal or Lateral.

CRITERIA

Use NRCS Engineering Technical Releases (TR), 210-25, Design of Open Channels; NRCS National 

Engineering Handbook (NEH), Part 653, Stream Corridor Restoration: Principles, Processes, and 

Practices; and NRCS NEH, Part 654, Stream Restoration Design, as applicable in surveys, planning, site 

investigations, and design of channel work.

Do not modify the horizontal or vertical alignment of a channel to the extent of endangering the stability of 

the channel or its laterals.

Capacity. Determine the capacity for open channels according to procedures applicable to the purposes 

of the channel and according to related engineering standards and guidelines in approved references 

and handbooks. Designs must consider low flows, average flows, frequent storm flows, and high 

(infrequent) storm flows.

Determine the water surface profile or hydraulic grade line for design flow using guidelines for hydraulic 

design in NRCS TR-210-25 and/or NRCS NEH, Part 654. Select a Manning’s n value for the condition 

representing an aged channel. Base the selection on the expected vegetation and other factors such as 

the level of maintenance prescribed in the operation and maintenance plan. Establish the required flow 

capacity by considering volume-duration removal rates, peak flow, or a combination of the two, as 

determined by the topography, purpose of the channel, desired level of protection, and economic 

feasibility. Design conditions cannot result in flood impacts to adjacent properties without addressing 

through the appropriate authorities.
582-CPS-2

NRCS, NHCP

September 2015

Cross section. Determine the required channel cross section and grade by the plan objectives, the 

design capacity, the channel materials, the vegetative establishment program, and the requirements for 

operation and maintenance. As necessary, provide a minimum depth to allow adequate outlets for 

subsurface drains, tributary ditches, or streams. In urban areas, consider the design impacts on highvalue developments.

Channel stability. A stable channel has the following characteristics:

 The channel neither aggrades nor degrades beyond tolerable limits

 The channel banks do not erode to the extent that an appreciable change in channel cross-section 

results

 Excessive sediment bars do not develop

 Gullies do not form or enlarge because of the entry of uncontrolled surface flow to the channel

Design all channel construction and modification (including clearing and snagging) to result in a stable 

channel with reasonable maintenance costs. Use vegetation, riprap, revetments, linings, structures, or 

other measures if necessary to ensure stability.

Use the methods in NRCS TR-210-25 and/or NRCS NEH, Part 654 to determine the stability of proposed 

channel improvements.

Bank-full flow is the discharge that fills a channel to an elevation where flow begins to spill onto the active 

floodplain.

Channels must be stable under conditions existing immediately after construction (as-built condition) and 

under conditions existing during effective design life (aged condition).

Determine channel stability for discharges under the following conditions:

 As-built condition.—Bank-full flow, design discharge, or 10-year frequency flow, whichever is 

smallest, but not less than 50 percent of design discharge. 

– The designer may increase the allowable as-built velocity (regardless of type of stability 

analysis) in the newly constructed channel by a maximum of 20 percent if—

o The soils at the site in which the channel is to be constructed are suitable for rapid 

establishment and support of erosion-controlling vegetation.

o Species of erosion-controlling vegetation adapted to the area and proven methods of 

establishment are known.

o The channel design includes detailed plans for establishing vegetation on the channel side 

slopes.

 Aged condition.—Bank-full flow or design discharge, whichever is larger, except that it is not 

necessary to check stability for discharge greater than the 100-year frequency.

Stability checks that are flow related are not required if the velocity is 2 ft/s (0.6 m/s) or less.

For newly constructed channels in fine-grained soils and sands, determine the Manning’s n values 

according to procedures in Chapter 6 of NRCS TR-210-25. Use caution selecting values greater than 

0.025. In channels modified by clearing and snagging, determine the Manning’s n value according to the 

expected channel condition following completion of the work. Guidance is also available in NRCS NEH, 

Part 654.

Appurtenant structures. Include all structures required for proper functioning of the channel and its 

laterals, as well as travel ways for operation and maintenance. Minimize the erosion or degradation from 

inlets and structures needed for entry of surface and subsurface flow into channels. Provide necessary 

floodgates, water-level-control devices, bays used in connection with pumping plants and any other 
582-CPS-3

NRCS, NHCP

September 2015

appurtenances essential to the functioning of the channels. If needed, use protective structures or 

treatment at junctions between channels, to ensure stability at these critical locations.

Evaluate the effect of channel work on existing culverts, bridges, buried cables, pipelines, irrigation 

flumes, inlet structures, surface drainage systems, and subsurface drainage systems.

Assure that culverts and bridges modified or added as part of a channel project meet reasonable 

standards for the type of structure and have a minimum capacity equal to the design discharge or state 

agency design requirements, whichever is greater. Increase the capacity of culverts and bridges above 

the design discharge as necessary to assure the channel and associated floodway meet design capacity.

In natural channels, evaluate the effect of the grade control structure on channel and bank stability. 

Determine backwater effects and the effects of modification of sediment transport through the reach.

Disposal of spoil. Dispose of spoil material from clearing, grubbing, and channel excavation in a 

manner that will—

 Not modify flows or cause channel instability when the discharge is greater than the bank-full flow.

 Provide for the free flow of water between the channel and floodplain unless the presences of 

continuous dikes establish the basis for the valley routing and water surface profile.

 Not hinder the development of travel ways for maintenance.

 Leave the right-of-way in the best condition for the project purposes and adjacent land uses.

 Direct water accumulating on or behind spoil areas to protected outlets.

 Maintain or improve the visual quality of the site to the extent feasible.

Vegetation of channel. Establish vegetation on all channel slopes, berms, spoil, and other disturbed 

areas according to CPS Codes 342, Critical Area Planting; or 580, Streambank and Shoreline Protection.

Cultural resources. Consider existence of cultural resources in the project area and any project impacts 

on such resources. Consider conservation and stabilization of archeological, historic, structural, and 

traditional cultural properties when appropriate.

CONSIDERATIONS

Visual resource design. Carefully consider the visual design of channels in areas of high public 

visibility and those associated with recreation. The underlying criterion for all visual design is 

appropriateness. The shape and form of channels, excavated material, and plantings are to relate 

visually to their surroundings and to their function.

Fish and wildlife. This practice may influence important fish and wildlife habitats such as streams, 

creeks, riparian areas, floodplains, and wetlands. Evaluate aquatic organism passage concerns (e.g., 

velocity, depth, slope, air entrainment, screening, etc.) to enhance positive impacts and minimize 

negative impacts.

Select project location and construction methods that minimize the impacts to existing fish and wildlife 

habitat.

Include measures necessary to mitigate unavoidable losses to fish or wildlife habitat in the design. 

Maintain the quality of the landscape by both the location of channel works and plantings, as appropriate.

Vegetation. Stockpile topsoil for placement on disturbed areas to facilitate revegetation.

Consider placement and selection of vegetation to improve fish and wildlife habitat and species diversity.

Water quality. Consider the effects of—
582-CPS-4

NRCS, NHCP

September 2015

 Erosion and the movement of sediment, pathogens, and soluble and sediment-attached substances 

that runoff carries.

 Short-term and construction-related effects of this practice on the quality of downstream 

watercourses.

 Wetlands and water-related wildlife habitats.

PLANS AND SPECIFICATIONS

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

this standard. 

As a minimum, include the following items:

 A plan view of the layout of the channel and appurtenant features

 Typical profiles and cross sections of the channel and flood plain, as needed

 Appurtenant features as needed

 Structural drawings, as needed

 Requirements for vegetative establishment and/or mulching, as needed

 Safety features

 Site-specific construction and material requirements

OPERATION AND MAINTENANCE

Prepare an operation and maintenance plan for the operator.

As a minimum, include the following items in the operation and maintenance plan:

 Periodic inspections of all structures, channel surfaces, safety components and significant 

appurtenances.

 Prompt repair or replacement of damaged components.

 Prompt removal of sediment when it reaches pre-determined elevations.

 Periodic removal of undesirable trees, brush, and invasive species.

 Maintenance of vegetative protection and immediate seeding or replanting of damaged areas, as 

needed. 

REFERENCES

USDA Natural Resources Conservation Service. Engineering Technical Releases, TR-210-25, Design of 

Open Channels. Washington, DC.

USDA Natural Resources Conservation Service. National Engineering Handbook (NEH), Part 653, 

Stream Corridor Restoration: Principles, Processes, and Practices. Washington, DC.

USDA Natural Resources Conservation Service. NEH, Part 654, Stream Restoration Design. 

Washington, DC.