Wetland delineation
The dual pedological and floristic criterion
Wetlands are delineated on a dual criterion, pedological (soil) and floristic (vegetation).
Wetland delineation
Wetlands are delineated on a dual criterion, pedological (soil) and floristic (vegetation). ARKENOR characterises and maps wetlands to secure water-law files and the Avoid-Reduce-Offset sequence.
Definition
A wetland is delineated by protocol, not by appearance.
Whether land qualifies as a wetland is determined by defined criteria applied in the field, soil morphology and vegetation, following a protocol, not by whether the ground looks wet. Land that is dry for most of the year routinely qualifies, and this is where projects are most often caught out.
The consequence is significant: works affecting a delineated wetland trigger regulatory obligations including, in many cases, a Water Act file, and compensation ratios for wetland loss are among the most demanding in French environmental practice.
Timing
Delineate before the layout is fixed.
Because wetland delineation can remove developable area, it belongs at the feasibility stage. A delineation carried out after the masterplan is drawn produces one of two outcomes: a redesign, or a compensation obligation heavy enough to change the project's economics.
Soil survey and vegetation survey are both required, and vegetation is only readable in season, another reason the ecological calendar governs the programme.
Consequence
What delineation changes for the scheme.
A delineated wetland is not automatically undevelopable, but building on it triggers the heaviest compensation ratios in French environmental practice, alongside a Water Act file. In most schemes the arithmetic favours avoidance: redrawing the layout costs less than acquiring and managing compensation land for decades.
That arbitration can only be made while the layout is still open, which is why delineation belongs to feasibility rather than to the permit file. Discovering a wetland after the masterplan is approved converts a design question into a financial one.
Going further
Related pages.
Wetland delineation feeds several procedures.
- Water Act file — triggered by works on wetlands
- Offsetting measures — wetland ratios are among the heaviest
- Four-season surveys — vegetation is only readable in season
- Natural component (VNEI) — where delineation is reported
- Environmental impact assessment — the containing file
- Green and blue network — wetlands as ecological corridors
- Working with land developers — where delineation changes the scheme
- Ecological expertise — the full set of procedures
- Avoid-reduce-offset sequence — why avoidance usually wins here
- Net Zero Land Take — the wider constraint on developable area
Discuss your project
Engineering, environmental advisory and independent certification under one group, with a strict separation of roles.
Sans engagement · Réponse sous 48 h ouvrées · Données confidentielles