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Marais de Sacy Association        FR


The Sacy Marsh was a lake under the Roman Empire; it was occupied and exploited by human being for a long time as nearby archeological research proved.

The first specific elements on its exploitation are dating from the 16th Century. During that time big hydraulic works have been done such as: extracting peat, digging channel (including Frette River), building hydraulic structure and so on.


The area was split between towns to be used for agricultural purposes: grass was cut for fodder or bedding for animals, the less wet surfaces were used as crops.

Watercress beds were developed in the North of the wetland in the early XIXth century and almost disappeared in the 70's.

All those economic activities have shaped the present landscape, leaving ponds, straight drainage canals and artesian wells behind.   

Currently, one fourth of the site is owned by a local public institution "Conseil départemental de l'Oise" (240 ha), while more than another quarter belongs to the surrounding towns (300 ha) and 460 hectares are managed by private owners.

Nowadays, Hunting (big and small games, mainly ducks) is among the main activities in the marsh, followed by fishing and relaxing.


Geographical Location

Close to the Oise Valley, the Sacy Marsh is located in a triangle made by Clermont de l'Oise, Compiègne and Creil. It's a massive peaty wetland (fen) of 1000 hectares with important ecological and patrimonial issues. It is surrounded in the South by forest and in the North by meadows, poplar plantations and crops (cereals and market gardening).

The Sacy Marshes are under an oceanic climate. Their elevation is between 32 and 62 meters, the water comes from the aquifer (Artesian wells and springs) in the North and mostly from the rain in the south. 

Marshes are drained in their center by a river called "Frette" which flows to the Oise River in Pont Sainte Maxence town. Under "downloads" you will find a document presenting geological, hydrogeological and hydraulic network of the Sacy Marsh.

Flora and Fauna

Sacy Marsh is a vast set of mire (peaty wetland) mainly alkaline with small acid parts (in the south). The wetland is a patchwork of natural mediums characterized by homogeneous conditions (water, forest, meadows, reedbeds...) and typical fauna and flora species. The environment consists predominantly of reedbeds with Cladium mariscus and/or Phragmites australis.

Those natural habitats change gradually under the influence of different parameters, natural and anthropogenic, coming from inside or outside the area. Generally, marshes and mires change from aquatic medium to forest, every step of this change has its own indicator species.


The main natural habitats of Sacy marshes are:

  • Running water, made of rivers, channels, where plants such as Ranunculus or water starworts (Callitrichaceae) grow;
  • Fresh still water (ponds) with the associated flora, floating or submerged aquatic plants (Characeae, Potamogeton coloratus...)
  • Pioneer peaty habitat (over bare peat)
  • Reedbeds consisting of different species
  • Wet grazed meadows characterized by moor grass (Molinia caerulea) and  rush (Juncaceae),
  • Mesophilic meadow,
  • Wet Shrubs: they are dominated by Grey willow (Salix cinerea) in shape of "ball" is typical of the landscape of the marshes.
  • Forest: they are natural or anthropogenic (poplar in the surrounding of the marsh).

Among the interesting plants we can name the Marsh Gentian (Gentiana pneumonanthe), Willowleaf yellowhead (Inula salicina), Common cottongrass (Eriophorum angustifolium), Marsh helleborine (Epipactis  palustris) and bladderworts (carnivorous plants living in the ponds) etc.


Fauna species are an important issue for the Sacy Marsh including amphibians like the Great crested newt (Triturus cristatus) and the European tree frog (Hyla arborea). Birds like the Great Bittern (Botaurus stellaris), the Little Bittern (Ixobrychus minutus), the Bluethroat (Luscinia svecica) or the Common snipe (Gallinago gallinago) enrich the area. Many species of insects are also a strong patrimonial issue: Large White-faced Darter (Leucorrhinia pectoralis), Short winged Conehead (Conocephalus dorsalis), Large Marsh Grasshopper (Stetophyma grossum), Large Chequered Skipper (Heteropterus morpheus) etc. Other classes represent also an ecological concern like the Fen raft spider (Dolomedes plantarius) and molluscs such as Desmoulin's whorl snail (Vertigo moulinsiana) or Narrow-mouthed whorl snail (Vertigo Angustior).

Current challenges

Various problems affect this area:

  • Marsh aggradation leading to a natural development from a marsh to a forest intensified by the next parameter,
  • Digging canals and ponds due to peat extraction and hydraulic projects, causes strong drainage of the wetland,
  • Lack of maintenance of herbaceous habitat (closing of the environment),
  • Lack of coordination on the water management ,
  • Water withdrawals (drinkable water, agriculture),
  • Pollutions from the drainage basin (nitrate, phosphate, hydrocarbon...),
  • Non native invasive plants competing with natural vegetation.

The solutions, Marais de Sacy Association has developed can be found under Projects and Natura 2000.

Protected areas

Sacy marsh is classified in multiple protection regulations. 

It is a Sensitive Natural Area (FR : Espaces Naturels Sensibles) under French law. This designation given by the local public administration "Conseil départemental de l'Oise" allows to apply for financial support for some of the specific projects. Further on, a pre-emptive right on a definite area can be established. In this frame, "Conseil départemental de l’Oise" acquired 240 hectares in 2001.

The wetlands of Sacy are integrated in the Natura 2000 network. In 2005, a management plan (Objectives Document) was confirmed, and the designation for Habitat Directive Site was published on the 21st of December 2010.