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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. 

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Natural Resources Conservation Service 

CONSERVATION PRACTICE STANDARD 

HILLSIDE DITCH 

CODE 423 

(ft)

DEFINITION 

A narrow channel with a supporting ridge on the lower side, constructed across the slope on steeply

sloping land. 

PURPOSE 

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

• Reduce erosion by reducing slope length 

• Increase infiltration throughout the slope 

• Divert runoff from sloping upland areas to a stable outlet 

CONDITIONS WHERE PRACTICE APPLIES 

This practice applies to steeply sloping sites where there is sufficient soil depth for construction of a ridge

and channel. 

Do not use a hillside ditch to protect buildings, roads, or other improvements. Use NRCS Conservation

Practice Standard (CPS) Diversion (Code 362) for that purpose. 

CRITERIA 

General Criteria Applicable to All Purposes 

Location 

A hillside ditch usually has a small, shallow channel and is constructed by hand in most cases. In many

cases multiple hillside ditches are applied as a system and are installed at controlled gradients at defined

horizontal intervals. Locate the hillside ditch or ditch system to fit the land condition and the cropping

system. For instances where it is feasible to install a vegetative barrier as a supporting practice, apply it

immediately upgradient of the hillside ditch in accordance with the criteria in NRCS CPS Vegetative

Barrier (Code 601). 

Channel stability and capacity 

Channel grades may be uniform or variable. Determine minimum depth and width requirements for

channel stability by using the procedures in the NRCS National Engineering Handbook (Title 210), Part

650, Chapter 9, “Diversions.” Design a stable channel based on the limiting stress on the soil and

vegetation such that soil particles will not be detached, and the vegetation will not be damaged. The

capacity of a vegetated channel will be based on the densest and longest vegetation resulting in the

highest expected retardance. 

Determine the hillside ditch length to match the cropping system and to limit the contributing drainage

area. Large runoff volumes from larger drainages can require channels too large for site constraints. The

maximum allowable length of a hillside ditch draining in one direction is 500 feet. 
Design a hillside ditch to convey the peak discharge from a 5-year frequency, 24-hour duration rainfall

event. 

Horizontal spacing 

For multiple hillside ditches applied as a system, use table 1 to determine the maximum horizontal

spacing. 

Table 1. Hillside Ditch Horizontal Spacing 

Protection against sedimentation 

Excess sediment accumulation in the hillside ditch channel lessens hydraulic capacity and impedes flow.

For a contributing drainage area that produces a high sediment load, incorporate measures to limit the

accumulation of sediment in the channel such as— 

• Installing conservation practices such as land treatment, erosion control, cultural or tillage, or

structural measures. 

• Installing any needed conservation practices in conjunction with or before construction. 

• Increasing the channel size to accommodate the estimated sediment accumulation (e.g., 1-year or

2-year) unless the operation and maintenance plan specifically addresses the periodic removal of

sediment. 

Outlet 

Locate or establish a stable outlet prior to the construction of the hillside ditch. An outlet may be a grade

control structure, a natural or constructed waterway, a stable watercourse, or a stable disposal area such

as a well-established pasture. Use criteria in NRCS CPS Grassed Waterway (Code 412) for a grassed

waterway outlet; Lined Waterway or Outlet (Code 468) for a lined waterway; and Grade Stabilization

Structure (Code 410) for grade control structures. 

CONSIDERATIONS 

Additional conservation practices that improve soil function, permeability, and structure can reduce runoff

and sedimentation from the contributing drainage area, reducing the required size of a hillside ditch.

Consider applying additional land treatment, erosion control, and cultural or tillage practices with the

hillside ditch. 

When planning a hillside ditch, consider the following as applicable: 

• Effects on the water budget, especially effects on volumes and rates of runoff, infiltration,

evaporation, transpiration, deep percolation, and ground water recharge. 

• Filtering effects of vegetation on movement of sediment and dissolved and sediment-attached

substances. 

• Potential to borrow a portion of the material needed to construct the ridge from downslope of the

ridge to effectively reduce the average slope between successive hillside ditches. 

• Short-term and construction related effects of this practice on the quality of downstream water. 

• Potential advantages of NRCS CPS Vegetative Barrier (Code 601) compared to a Hillside Ditch on

steep fields with sandy soils. 

• Potential for development of saline seeps or other salinity problems resulting from increased

infiltration in the presence of restrictive layers. 

Land Slope (percent) Maximum Spacing (feet)

<12 40

12–25 35

26–40 25

>40 20

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• Potential to affect significant cultural resources. 

PLANS AND SPECIFICATIONS 

Prepare plans and specifications for constructing hillside ditches that describe the requirements for

applying the practice to achieve its intended purpose. As a minimum, the plans and specifications must

include— 

• A plan view of the layout of the hillside ditch or the ditch system. 

• A profile of the hillside ditch that includes both the channel bottom and any supporting ridge top. 

• Typical cross sections of the hillside ditch. 

• Quantities and material requirements. 

OPERATION AND MAINTENANCE 

Prepare an operation and maintenance plan for the client. Include specific instructions for maintaining

capacity, storage of runoff water, ridge height, and outlets in the plan. As a minimum include— 

• Conducting periodic inspections, especially following significant storms. 

• Promptly performing maintenance and repairs as necessary. 

• Removing accumulated sediment in accordance with the planned schedule or periodically as

necessary. 

• Removing vegetative growth or debris interfering with the proper functioning of the ditch. 

• Removing debris interfering with the outlet operation, as necessary. 

• Maintaining well-established vegetation in the outlet to provide stability. 

REFERENCES 

Food and Agriculture Organization of the United Nations. 1988. Conservation Guide 13/3, Watershed

Management Field Manual, Slope Treatment Measures and Practices. Rome, Italy.

http://www.fao.org/3/ad083e/AD083e00.htm#cont

USDA NRCS. 2021. National Engineering Handbook (Title 210), Part 650, Chapter 9, Diversions.

Washington, D.C. https://directives.sc.egov.usda.gov/

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