Erosion TTool/Creating a retention pond or restoring wetlands
A pond is a natural or artificial depression of shallow depth (2 to 3 m maximum) where water can be present temporarily or permanently. It does not include a drainage structure, which differentiates it from ponds[1]. To limit erosion, the pond is divided into 2 levels: a deeper level where water is permanently present; a shallow level that serves to regulate flow and will only be filled during a runoff event. It is therefore preferable to provide a spillway to evacuate excess water[2].
Description
Advantages
- Allows to increase biodiversity.
- Reduces flooded areas and runoff flow.
- Water storage to water livestock.
Disadvantages
Downstream of plots very sensitive to erosion, the pond silts up very quickly: soil must be able to settle before reaching the pond.
Recommendations
- Any installation of a pond (regardless of its size) must be the subject of a declaration at the town hall, with the Inter-Service Water and Biodiversity Mission (MISE or MISEB).
- The recommendations of departmental health regulations must be respected (often 35 m maximum from water points and 50 m from dwellings).
- Ponds must be listed in the PAC declaration as "topographical features".
- It is preferable to install a grass strip at the edge of the pond, or even a hedge.
- The pond must be regularly maintained, notably by dredging.
Alternatives
Wet depressions. This is a particular type of pond corresponding to the wettest areas of plowed fields. It can be defined as a temporary wetland.
