Government of New Brunswick


Surface drainage is the orderly removal of excess water from the surface of land through improved natural channels or constructed ditches and through shaping of the land.



2.1 Open Channels


2.1.1 Open Ditch:A channel constructed to collect excess water and to conduct it to a safe outlet.
2.1.2 Diversion Ditch: A channel constructed across the slope of the land to intercept surface runoff.
2.1.3 Tile Drain Interceptor: A channel located to collect water from a subsurface drainage outlet.
2.1.4 Dale Ditch: A small channel excavated by a rotary ditcher on dykeland.
2.1.5 Vent Ditch: A channel that collects water from dale ditches.
2.1.6 Inner Dyke Ditch: A channel running parallel to a dyke. This ditch collects the water from vent ditches and conducts it to a water control structure.
2.1.7 Common Main Drain: A channel that serves as an outlet for a number of ditches from different farms.


2.2 Land Shaping


2.2.1 Dykeland Forming: The crowning of marshland by mechanical movement of soil to improve surface drainage and farmability.
2.2.2 Upland Forming: The process of cut and fill to eliminate major depressions in a field resulting in increased runoff and improved drainage and farmability.
2.2.3 Land Levelling: Smoothing the land surface with a land leveller to eliminate minor depressions in a field without changing the general topography.


3.1 All surface drainage design and construction shall be in accordance with the America Society of Agricultural Engineers Engineering Practice - A.S.A.E. EP 302.2 - Design and construction of surface drainage systems on farms in humid areas
3.2 The system shall be designed as an integral part of soil and water facilities, the farm layout, and cropping plan.
3.3 Good quality construction is essential for adequate drainage. Qualified engineers should be responsible for surveys, designs, layout and checking to guarantee that construction meets specifications. Land-owners and contractors shall be provided with the information necessary for good quality construction
3.4 Consideration shall be given to prevent excessive erosion resulting from any surface drainage system.
3.5 The design and construction of agricultural surface drainage systems shall comply with NB Department of Environment Watercourse Alteration Regulations and guidelines and Regulation 90-80 and 90-120 under the Clean Water Act as revised in 1993.
3.6 The design and construction of agricultural surface drainage systems shall comply with NB Department of Environment Watercourse Alteration Regulations and guidelines and Regulation 90-80 and 90-120 under the Clean Water Act as revised in 1993.


4.1 Open ditches shall normally be dug during the period of June 1 to September 15 when there will normally be low flows of water thus limiting the amount of sediment that can be transported.
4.2 The design ditch bottom grade shall be no less than 0.05 percent. The maximum grade shall not result in the design/permissible velocity being exceeded.
4.3 The ditch bottom width shall be a minimum of 0.45m (1.5 ft.) and excavated to the lines and grades as required to meet this standard. Banks should be free from projections or other irregularities which will impede normal flow. Banks should be seeded with a recommended grass mixture within three days of construction.
4.4 Open ditch side slopes shall not exceed the following:
Soil Shallow Channels
< 1.2m (4') in depth
Deep Channels
> 1.2m (4') in depth
Peat and Muck Vertical 0.25 : 1
Heavy Clay 0.5 : 1 1 : 1
Clay or Silt Loam 1 : 1 1.5 : 1
Sandy Loam 1.5 : 1 2 : 1
Loose Sand 2 : 1 3 : 1
4.5 The spoil from the ditch excavation should be placed a minimum of 3.0m (10 ft) from the edge of the ditch and shall be leveled to a maximum grade of less than 0.3m above original ground.
4.6 Open ditches shall be designed to safely discharge the peak flow resulting from a 10 year - 24 hour rainfall. The design peak flow shall be increased in critical areas (municipal/housing areas, etc.).
4.7 The design discharge used to determine the open ditch capacity shall be calculated using the USDA-SCS EFM2 method or the TR55 method.
4.8 On steep grades, or highly erodible soils, or also where the design peak discharge and/or design velocity is greater than the permissible, the ditch shall be designed with a stone center, appropriate erosion control matting or other systems to safely discharge peak flow.
4.9 Settling basins should be installed to allow the water to slow down and any silt to settle out. The dimensions of the settling basin shall be a minimum of 0.6m (2 ft) deeper than the ditch bottom, a length equivalent to ten ditch bottom widths, and a width of two times the ditch bottom width. The side slopes of the settling basin should be the same as the ditch.
4.10 Any culvert to be installed in an open ditch shall meet the following criteria:
  4.10.1 Minimum diameter of culvert to be 150mm (6").
  4.10.2 Culverts shall be manufactured of galvanized steel, concrete or high density polyethylene and meet the following standard: Galvanized steel
CSA G 401-M 81 Concrete
CSA A 257.3 M 1982 - for 150 mm <O.D.> 300 mm
CSA 257.2 M 1982 - for 300 mm <O.D.> 3700 mm High density polyethylene
ASTM F 667 - 87 A - for 150 mm <O.D.> 400 mm
AASHTO M 294 - 851 - for 400 mm <O.D.> 750 mm
  4.10.3 The culvert diameter shall be designed to safely discharge the peak flow resulting from a 10 year - 24 hour rainfall. The design peak flow shall be increased in critical areas (municipal/housing areas, etc.).
  4.10.4 Culverts shall be backfilled in a manner to prevent erosion, settling, culvert damage and to permit safe crossing.
4.11 A buffer strip of 2.0m (6.5 ft) should be maintained parallel to the ditch banks. Tillage operations should not be carried out within this zone. Livestock access should also be denied within this zone to prevent the breakdown of the ditch banks.
Figure 1. Typical Open Ditch Cross Section.


5.1 The field area contained in one land form, which is the area of land located between the center-line of the runs on either side of the crown and the ends of the form, shall be no less than 0.8 hectares (2.0 acres) unless the total maximum length of the form as determined by the project engineer and must be less than 152.4m (500 feet).
5.2 The width of a single form, which is the perpendicular distance measured from the center-line of one run to the center-line of the nearest run, shall be no less than 36.6m (120.0 feet) and no greater than 3.0% of the full length of the land form
Figure 2. Typical Dykeland Forming Cross Section.


5.3 Land forms within the same field shall be constructed parallel to each other and shall be as close to rectangular in shape as possible.
5.4 The side slope of the crown of a land form is measured from the average level of the run or top of the run ditch to the average level of the center of the crown and shall be no less than 2.0% and no greater than 3.0% for the full length of the land form.
5.5 Land forms shall be constructed according to the lines and grades established by the project engineer or designate. Crowning shall be constructed so all crowns are free of pockets or depressions. Crowns shall be land smoothed after rough construction.
5.6 Land smothers (land leveler) shall be passed over the field surface at least 3 times as a finishing operation. The first two passes shall be on opposite diagonals and the last pass shall be in the row direction.
5.7 Grading shall be checked prior to and following finishing operations. A tolerance of 30 mm (0.1 ft) may be allowed in checking, providing there are no reverse grades in row direction.
5.8 Land form run ditches shall be constructed to a minimum depth of 0.3m (1.0 ft) and shall drain freely.


6.1 Topsoil shall be removed from both the cut and fill areas prior to subsoil movement.
6.2 Low areas shall be filled and graded as required to improve surface drainage.
6.3 Topsoil shall be replaced and levelled to final grades.


7.1 Upon notification of project completion, the project engineer or designate will carry out final inspection and report of the site.
7.2 Projects will only be consider complete if they meet these standards and work is suitable to the project engineer or designate.

The New Brunswick Department of Agriculture, Fisheries and Aquaculture reserves the right to revise the above standard at any time.