Drainage is the step of artificially favor the evacuation of the water present in the top layer of soil. The realization of drainage networks (ditches and / or drains) is subjected bonds.

What that drainage?

Drainage is the step of artificially favor the evacuation of the water present in the top layer of soil.

This evacuation of water stored in the soil can be done using agricultural drains (perforated plastic tubes) buried in the soil to a depth and a calculated distance but also with ditches.

Not a drainage:

recalibration of a waterway by deepening the bUsage a river. Warning streams are sometimes mistaken for ditches. If in doubt, see How to differentiate a stream of a ditch (later given link), the laying of a collection of a source line.

The regulatory environment and obligations

The realization of drainage systems is subject, reading of the Environmental Code, a procedure Water Act (Section 3320 of the Water nomenclature) based on the land area drained:

greater than or equal to 100 ha = authorization procedure greater than 20 ha but less than 100 ha = Procedure Declaration.

In short, if your combined total surface drains (drains and drains project already done) to the scale of operation exceeds 20 ha: the project is subject to declaration or authorization under the Water Act.



For more information: Comment be a "water law" file for any project affecting aquatic environments

Other sections of the Water nomenclature are involved in the achievement of most of the drainage networks, including (non exhaustive list):

section 3310 (draining of wetlands), section 3150 (destruction of spawning grounds), sections 3110, 3120, 3130, 3140 (River works), section 2150 (collection of runoff), items 2 ... (releases).

Any surface consider?

For drainage systems made before March 29, 1993:

Drainage systems achieved before can March 29, 1993 continue to be operated upon to be brought to the attention of the Prefect.

Your file "brought to knowledge" must be made:

a cadastral plan on the scale of the operation that reveals the drained plots (county, section, parcel number, owner ...), their surface and drainage technique used (pipe, ditch ...) an identification of the discharge points in the natural environment (rivers or other).



For drainage systems made after March 29, 1993 but not allowed:

The drainage systems made after March 29, 1993 must be the filing of a regulatory compliance folder in the forms of a Water Act folder (Declaration or authorization). The file must contain a disclosure implications or impact study for Authorizations (Annex paragraph 13-b of art. R122-2 of the Environmental Code).



For drainage systems to achieve:

Drainage systems to state in your application or Declaration of Entitlement under the water law combine the networks already installed with the project networks. The summation is farm.



The mapping of existing drains will be on file, as well as the project drains.

And on releases of drains?

Any modification, creation or implementation of a drain discharge structure is subject to a procedure of declaration or authorization Water Act, even if the cumulative total area drained the scale of your operation is less than 20 ha .

These obligations apply the discharge into a stream (or channel) or in a ditch.



For more information: Ditches: obligations and recommendations (available later link)

The main environmental impacts of drainage

On water resources and aquatic environments:

Drainage, well beyond the decline of the ceiling of the surface water, generates significant impacts, direct and indirect, immediate and delayed, on the ecology of the landscape and waterways.

It sometimes leads to ecological and physical alteration of the landscape and natural environments or certain agricultural systems where it has been practiced to increase arable areas or intensity of agriculture, especially in the case of extensive drainage wetlands.

When they are large or excessive, drainage operations can cause or exacerbate droughts, fires or promote degradation of peat soils, and affect some tree species (alder, poplar, ash) in their growth, but also for Natural regeneration of their stands.

The alluvial valleys and woodlands and bogs, are the areas that were most drained, causing the artificial wetland loss associated. The modernization of drainage techniques (eg integrated lift pumps), has often disappear within decades major networks streams, ditches, flood expansion areas and unregulated rivers, with consequently a water reduction Locally available for wildlife and natural flora, and sometimes for the local drinking water supply, recreation, fishing, seriously obérant potential restoration of biodiversity and soil that helps to degrade.

On Water Quality

The drainage system drains directly into the trenches and / or river large amounts of nitrates, phosphates, and pesticides (pesticides) drained through the soil.

Thus, the concentrations of various parameters in the drain waste water may exceed the limit of good water status defined by the regulation (European Water Framework Directive in particular), especially during rainy periods.

Furthermore, studies show that in dry weather, concentrations of nitrates and pesticides are more important in the discharge of drains in the receiving waters.

+ The technique:

Thresholds of good water status set by the Water Framework Directive:

nitrate discharge> 50 mg / l, rejection SS (suspended solids)> 50 mg / l, total rejection pesticides> 0.5 mg / l ...



In dry weather, rejection is translucent and does not pollute.

Fake !!! Even in dry weather, dumping drainage contains pollutants, although the concentrations are lower than during rainy periods. In rainy weather, the brown color of the discharge of drains is from suspended matter which can, by chemical reaction, accentuate the character of toxic pollutants.





Attention defects Authorization or Declaration is liable to administrative and judicial sanctions provided for in the Environmental Code.

Related regulatory references:

Article L211-1 of the Environmental Code: aims to ensure the preservation of the particular aquatic ecosystems, sites and wetlands. Wet area means the land, exploited or not, usually flooded or waterlogged fresh, salt or brackish permanently or temporarily vegetation, when it exists, is dominated by hygrophilous plants for at least part of the year. Article L432-3 of the Environmental Code: the fact of destroying the spawning grounds or areas of growth or supply of fish fauna is punishable by a fine of ? 20,000, unless it results from an authorization or a declaration that the requirements have been met or emergency work performed to prevent a serious and imminent danger. Décret 2008-283 of 25 March 2008 on the spawning grounds and areas of growth or supply of fish fauna: sets the criteria for defining spawning and nursery areas and modalities of identification.