The Audomarois marsh: history, fauna, flora and traditions
The Saint Omer marsh, a natural area recognized by UNESCO
The marshes of Saint-Omer and Clairmarais: a must-see destination in Audomarois
Just 40 minutes from Calais and Dunkirk, and 1 hour from Lille, the Audomarois marsh opens the doors to a world apart. This natural gem of the Hauts-de-France region awaits you for an exotic getaway, rich in history and authenticity.
On the agenda: guided boat tours, rowing and motorboat rides, hiking and biking, and cultural outings in the beautiful town of Saint-Omer. A real breath of fresh air between city and nature!
Located between inland Flanders to the east and the hills of Artois to the west, the Audomarois marsh extends across 15 communes in the Nord and Pas-de-Calais regions. These include: Saint-Omer, Clairmarais, Serques, Éperlecques, Houlle, Moulle, Salperwick, Tilques, Saint-Martin-lez-Tatinghem, Longuenesse, Arques, Watten, Saint-Momelin, Noordpeene, and Nieurlet.
The Audomarois marsh in a few words
This labyrinth of land and water stretches over 3 hectares (700 km²), crisscrossed by more than 37 kilometers of waterways, 700 of which are navigable! These figures attest to the immensity of this natural gem, classified as a Biosphere Reserve by UNESCO. But beyond its dimensions, the Audomarois marsh also impresses with its historical richness and its major ecological role.
In the past, this vast peaty wetland was still influenced by the high tides via the Aa River, particularly during the Carolingian era. Gradually, humans took over these lands: the monks of Sithiu (the former name of Saint-Omer) and the Clairmarais Abbey extracted peat from them. Farmers poldered the land, dug drainage canals to channel water to the sea, and channeled the main waterways to enable the growth of trade in Saint-Omer.
In the 19th century, the marshland took on its current form: a space that is simultaneously inhabited, wild, and cultivated. Market gardeners still perpetuate the tradition of growing Saint-Omer summer cauliflower and winter endive.
A discreet destination but full of surprises, the last market garden marsh in France delights hikers, fishermen and nature lovers in search of peace and authenticity.
Climb aboard traditional boats—escutes and bacôves—for a trip along the water. The region's last remaining boat builders invite you to experience a unique cruise in the heart of a landscape shaped by man and preserved by nature.
Let’s discover the Audomarois marsh together: its history, its fauna, its flora… and its well-kept secrets.
In summary
The Audomarois marsh in a few figures
As indicated above, the Audomarois marsh covers 3 hectares, or just over 726 km². This is the largest wetland from the entire Hauts-de-France region.
To give an idea, the marsh is approximately 12 times larger than the hortillonnages of Amiens, and it counts 4 times more riversThis vast natural basin has an average altitude of 0 meters, and some points can go down to one meter. below sea level. A configuration that makes the area very vulnerable to rising waters.
If a few hundred hectares belong to public actors (the Hauts-de-France Region, the Pas-de-Calais Department, Eden 62, the municipalities of Saint-Omer and Clairmarais, the Regional Natural Park, the Coastal Conservatory, etc.), 90% of the marsh is private.
There are more than 13 plots distributed among 000 owners.
On the agricultural level, the marsh includes approximately:
450 hectares of market gardening (including the famous cauliflower from Saint-Omer);
300 hectares of various crops (especially cereals);
1 hectares of meadows, part of which is devoted to thecattle and sheep farming.
This mosaic of owners and uses makes the Audomarois marsh a living, agricultural and fragile territory, both shaped by man and subject to natural hazards.
The Audomarois marsh: 13th century of labor
The Saint-Omer marsh during Antiquity
A marsh developed by monks in the early Middle Ages
In the 7th century, during the reign of Dagobert I, three monks from Luxeuil—Mommelin, Bertin, and Ebertram—settled in Morinie. Their mission: to convert the pagan Morin people to Christianity. At their head was Bishop Audomar of Thérouanne, a powerful figure in the clergy of the time.
The first monastery was founded on the present-day site of Saint-Mommelin. But the location, too exposed to flooding and attacks, quickly proved unsuitable.
According to legend, the three monks then boarded a boat and let themselves be carried by the waters, praying to God to guide them. They ended up landing on the heights of Sithiu, a more favorable, sheltered and higher place.
Another version of the legend says that these lands belonged to a pirate named Aldroad. Converted by Audomar, he would have offered all of his lands to the clergy, including the territories of the future communes of Saint-Omer, Clairmarais and Arques.
From Sithiu to Saint-Omer, a stronghold in the North
Unlike Saint-Mommelin, located on the edge of the marsh and close to the Gulf of Portus Itius, Sithiu offered many advantages:
A natural elevation of 12 meters, ideal for spotting enemies
A marsh surrounding the place three-quarters, forming a effective natural barrier
This strategic choice proved to be wise, because Saint-Omer suffered several waves of Viking invasions in the 9th century (→ see our dedicated article).
Gradually, the site is developing: construction of thelower abbey (Saint-Bertin, initially dedicated to Saint-Pierre), of theupper church (future cathedral), then a fishing village.
From the 10th century, Saint-Omer becomes a dynamic market place at the crossroads of Flanders and Artois.
In the 12th and 13th centuries, it became an important trading port, a religious and administrative stronghold, and an intellectual center of the Counter-Reformation during the Renaissance.
Saint-Omer developed from the XNUMXth century
In the 9th century, monks undertook the first hydraulic developments in the marsh. One of the major projects was the diversion of the Aa river towards Arques, thanks to the creation of the Lower Meldyck Canal. This canal, whose name means “flour” in Flemish (Maldyck), allows a local mill to be powered.
A second work, the Upper Meldyck, is then dug to carry the water to the foot of theAbbey of Saint-Bertin.
Around the 10th century, the first operations of land reclamation begin in the Audomarois marsh. The principle: drain certain parts of the marsh to gain arable land.
The furrows left by the Aa in the marshy basin are then widened and deepened to facilitate the flow of waterThe extracted mud is used for improve agricultural and livestock land.
This technique is applied progressively, in a logical order: high marshes (on the outskirts of towns) towards the low marsh (in the heart of the marsh). This process of land conquest extends to the end of the 17th century.
From there, we adopt the techniques from the Dutch polders : marshland bunding, dikes, water gates, and windmills to manage levels.
En 1866, the conquest of lands ends: no more new land will be “reclaimed from the water”.
Canal works and the era of maritime trade
Besides the creation of agricultural land and drainage ditches called water gangs, the inhabitants also had to fight against floods and develop navigation.
Around the year 1100, a vast canal named Nova A — or “Grand Large” — is dug. It crosses the marshes of Salperwick, Tilques, Serques, Houlle and Moulle.
This new river axis allows larger boats to travel and facilitates the flow of water from the Aa towards the sea, thus reducing the risk of flooding.
En 1165, Great River is in turn transformed into a canal. It serves the inland ports of Saint-Omer — notably the Quai du Haut-Pont, the Vain Quai and the Quai des Salines —, and connects them to the Gravelines seaportThis achievement is initiated by the Count Philip of Alsace.
These hydraulic developments have a dual objective: drainage et economic development.
In parallel, the Count of Flanders Baldwin VII continues the work started by his predecessor, Baldwin VI, which had already connected the basin of the Light to that of theAa via a wide defensive ditch. This ditch would later become the famous Neuffossé canal.
Finally, to better control the water downstream, a dike is built on the Flemish coast, allowing high tides to be contained and securing the land upstream.
Some key dates in the evolution of the Audomarois marsh
The history of the Audomarois marsh is also marked by a series of major technical developments. Here are some key milestones:
1681 : Creation of the Calais Canal, aimed at improving river connections to the sea.
1699 : Construction of the Vauban lock at Gravelines. She allows to regulate high tides by closing to prevent seawater from invading the Aa, and by opening to facilitate its flow towards the sea.
1753 : Creation of the Neuffossé canal, connecting theAa to the LysThis project strengthens the navigation routes between the North Sea and the interior. It is this canal that will be equipped with a boat lift (Fontinettes). The latter was capable of lifting barges over a height difference of 13,13m!
From there, the waterways made it possible, particularly during the Industrial Revolution, to connect Dunkirk to Lille via a series of channels:
canal of the Colme,
canal of theAa,
channel of Neuffossé,
Lys Canal,
Then Deûle.
This river organization fully integrates Saint-Omer in the major river trade routes of the North.
1958 : Last major upheaval of the Audomarois marsh with the closure of the Haut-Pont reach and the creation of large-gauge canalThis new route bypasses the city to accommodate barges much larger than the old Freycinet models.
Since then, the heavy boats are excluded from the city and cross directly natural space, profoundly modifying the geography and uses of the marshIn 1967, the Fontinettes boat lift was permanently replaced by a high-head lock.
A space recognized by UNESCO and other prestigious labels
RAMSAR and PNR
Le audomarois marshes is powered by a complex hydraulic network:
le Aa River,
many rainwater and runoff,
as well as two deep water tables, which play a key role in its ecological balance.
This territory is one of the two large wetlands of national and international importance of the region North–Pas-de-Calais, alongside the Scarpe–Escaut area.
As such, he benefits from several official protections :
He is classy Ramsar area, According to Ramsar International Convention signed in 1971 for the preservation of major wetlands around the world.
It also includes a Regional Natural Park (PNR), That of Romelaëre Ponds, recognized for its remarkable biodiversity and its role in hydraulic regulation.
This recognition confirms the importance of the Audomarois marsh as biodiversity reservoir, flood regulator, and exceptional natural heritage.
From 2013, the Audomarois marsh is also classified Biosphere reserve by UNESCO, as part of the program MAB (Man and Biosphere).
This recognition recognizes the unique balance between a remarkable natural ecosystem and territory shaped by human activity for over a thousand years.
Here, Man and nature are interdependent. Without regular interventions — like the cleaning of canals, le mowing or maintaining the banks —, the marsh would gradually return to its former wild state: an impenetrable wetland that is difficult to inhabit.
Ce management and maintenance work, passed down from generation to generation, is what allows the Audomarois marsh to remain today:
inhabited,
cultivated,
et welcoming to exceptional biodiversity.
The Saint-Omer marsh: perpetual maintenance
A maintained, inhabited and shared marsh
The maintenance of the Audomarois marsh is today entrusted to the seventh section of the watering holes, a structure dedicated to water management. Depending on the season, its agents intervene to:
clean the rivers,
mow the algae,
et strengthen the banks, notably thanks to the technique of fascination (laying bundles to stabilize the banks).
To carry out these operations, specialized equipment is mobilized: cranes, barges, mowers, etc.
In the past, these tasks were carried out by hand, using traditional tools such as:
le troupa (to redo the banks),
theedrack (to dig ditches),
la grep (shovel for extracting peat),
la baguette (solid net for pulling out the mud).
Today, the marsh is a living and shared territory. We come across:
several inhabitants,
several market gardeners and breeders,
several fishermen, hunters, walkers and tourists,
as well as athletes, especially by canoe or bicycle.
All coexist in respect of a fragile balance, necessary for the preservation of this exceptional natural environment.
The Audomarois marsh in the global network of biosphere reserves
Since 2013, the Audomarois marsh has been part of the 12 French biosphere reserves recognized by UNESCO, alongside emblematic territories such as:
la Camargue,
many Cévennes,
la Fontainebleau forest,
many Gardon Gorge,
theGuadeloupe archipelago,
or the Fango Valley in Corsica.
It is integrated into the MAB (Man and Biosphere) global network, which aims to:
reduce biodiversity loss,
improve the livelihoods of local people,
support sustainable development,
et promote the exchange of expertise on a global scale.
This classification confirms the Audomarois marsh in its role as living laboratory, where the balance between nature, culture and human development is at the heart of the priorities.
Natural heritage: the fauna and flora of the Audomarois marshes
Thanks to a mild climate, to the abundance of water and its rich peaty soils, the Audomarois marsh is home to a exceptional flora.
It includes:
over 100 remarkable plant species,
whose 25 protected species,
et more than 60 plant communities, some very rare or endangered.
The marsh alone is home to 50% of the aquatic flora of the Nord–Pas-de-Calais region and a a true plant sanctuary, one of a kind !
On the fauna side, the latest inventories are just as impressive:
240 species of birds nest or pass through the marsh, including:
le little bittern,
le great bittern,
le rose bush,
le Great crested grebe,
and Kingfisher.
26 species of fish populate its waters: pike, pikeperch, European eels...
And in the watergangs, rivers and ponds, live many amphibians (green and red frogs), dragonflies et grass snakes.
Some species are today threatened, as'common European eel, victim of the fragmentation of watercourses.
Others, on the other hand, proliferate in a problematic manner : this is the case of muskrat, which digs galleries in the banks and damages market gardeners' crops.
Cultural heritage of the Audomarois marshes and old memories
The visitor who loves old stones cannot cross theAudomarois without stopping in the old town of Saint-Omer. Her majestic cathedral, its ancient streets and its rich past make it an unmissable stopover.
Around the city, the marsh villages also testify to a remarkable heritage. In Clairmarais, we still admire an old one medieval farm, ruins of the Cistercian abbey, Romelaëre ponds reserve and Rihoult-Clairmarais state forest.
On foot, by bike or by boat, the destination seduces with its timeless charmIt is no coincidence that, from the 17th century, the bourgeoisie of Saint-Omer and Clairmarais appreciated the famous "water walks".
Ancient stories even claim that every good visitor had to contemplate the “floating islands” of the marsh. These were then piles of earth and vegetation forming real natural rafts, drifting with the water.
King Louis XIV himself, after taking Saint-Omer in 1677, would have lingered there.
These floating islands have now disappeared, gradually swallowed up by their own weight or destroyed by successive hydraulic developments. But their memory still floats in the marsh's atmosphere...
Flemish origins
While walking through the Audomarois marsh, the attentive walker will notice many names of rivers, ditches or place names in the Dutch consonants.
Names like Stackelwaert, Hongarwaert, Bogarwaert, Little Sea, Great Sea, Westbrouck, Little Leeck ou Grand Leeck punctuate the landscape, particularly in the marshes of Saint-Omer, Clairmarais, Saint-Martin-lez-Tatinghem, Salperwick, Tilques et Serques.
These names are the linguistic remains of the origin Flemish of Audomarois and bear witness to the antiquity of the hydraulic network.
Here are some keys to understanding:
Generate more means “lake” → the “Petite” and “Grande Meer” are former lakes converted into polders;
Leeck means “leak” or “outlet of a polder”;
Waert = channel ;
Brouck = swamp;
Electricity = current or flow.
These terms reflect a old, very technical relationship between men and water, from Flemish culture.
Other names this time Frenchified, appeared more recently. They often designate canals or areas developed after the annexation of Saint-Omer to France in the 17th century.
This is the case for names like:
La Redoute,
The Duck Farm,
The Rivièrette,
The Mussent,
or even areas once known for their floating islands.
This contrasting toponymy tells the story ofhistory of the territory, between Flemish culture, hydraulic development and French influence.
A specific rural habitat - The traditional marsh house
Once upon a time, the market gardeners of Saint-Omer
The marsh was cultivated as soon as it was first drained. The first so-called highlands appeared on the outskirts of the city from the XNUMXth century before gradually reaching the old muddy marsh crossed by the Aa.
The market gardening boom of the 18th and 19th centuries
The population of the marsh is experiencing significant growth in Eighteenth centuryThe gradual end of the feudal system allows a better land sharing and encourages the establishment of many market gardening families.
It was at this time, in 1751, what summer cauliflower is planted for the first time in the fertile soils of the Audomarois marsh. This vegetable will become one of the agricultural emblems of the territory.
Then comes the Industrial Revolution, which is disrupting the local economy. 1848, the arrival of the railway opens up new opportunities for market gardeners. Marsh vegetables can now be shipped quickly to major cities, especially Paris.
In the summer season, in May-June, the four-season merchants roam the streets of the capital, loudly praising the qualities of “First Saint-Omer” : fresh vegetables, straight from the marsh.
The market gardeners of the Audomarois marsh during the Belle Epoque
Between 1850 and 1870Near 400 families settle down to cultivate the lands of Saint-Omer, Clairmarais and neighboring municipalities.
This period coincides with the decline of peat exploitation, long extracted by the grapplers, the old peat bogs of the Audomarois marsh.
The appearance of coal, exploited massively in the coal mines of Artois, makes this plant fuel obsolete. Peat will only be used in times of war or shortage.
To compensate for this loss of activity, market gardeners are turning to new crops.
En 1920, they begin production of winter endive, a vegetable that helps ensure additional income in the low season.
Beside the summer cauliflower, the endive becomes another local agricultural specialty, illustrating the adaptability of the marsh's inhabitants.
Market gardening after the war
After World War II, the traditional market gardening in the Audomarois marsh begins a slow decline.
La international competition, technical progress and the emergence of new production methods make this agriculture increasingly difficult to maintain.
In the past, the parts of the marsh were only accessible by boatThe market gardener used the bacôve, a flat-bottomed boat, maneuvered by pole. It was used to transport his crops — sometimes up to 3,5 tons of cauliflowers —, but also his cheval, essential to his work on the land.
After the war, some went so far as to pair two or three bacôves side by side to load one there tractor, illustrating attempts to adapt to modernity.
Next to the bacôve, thefollow served as a small utility vehicle. More maneuverable, it was used to transport family, tools or small loads.
She slipped through narrow rivers and maneuvered with a rush, a long, flat oar used as a lever or a sculling oar.
Before the arrival of thermal and then electric engines, some wealthy market gardeners equipped their boats with a sledder, the ancestor of the outboard motor.
The great land consolidation (1972 - 1984)
At the late 1970s, the Audomarois marsh is profoundly transformed by a vast consolidation operation.
farm roads and bridges are fitted out, making more than 500 hectares accessible by land.
From then on, the traditional boats become useless, relegated to secondary or tourist uses.
On boat makers, once indispensable, are closing the doors of their workshops one by one.
La mechanization then provides a breath of fresh air to local market gardening, allowing the activity to survive in the face of increasing competition.
But the decline is clear. number of families living from market gardening decreases from decade to decade:
200 in the 1970 years,
110 in the late 1990s,
60 in the late 2000s,
et less than 35 today.
This slow erasure marks the end of an ancestral way of life, that of a swamp cultivated by water, for and with water.
Market gardening today - Between traditions and adaptation
Today, the market gardeners of the Audomarois marsh continue their activity with varied approaches.
Some work in monocultures, alternating cauliflower in summer et winter endive. Others perpetuate a diversified agriculture, sometimes in organic cultivation.
In all, nearly 50 varieties of vegetables are still cultivated in the marsh. Among them:
le summer cauliflower,
thewinter endive,
le cabbage,
le celeriac,
theGros Vert de Laon artichoke,
and Tilques carrot, emblematic of the territory.
In cultivated marshes, it is not uncommon to come across a market gardener or seasonal worker, standing up from 4 a.m., working “on the cool” for harvest the cauliflowers.
The cooperative is waiting for them at the end of the morning: deliveries are often made before noon, to ensure the freshness of the product.
This scene is repeated every year, especially between July and August, during the full period, when summer cauliflower is at its peak.
A know-how that endures, between ancestral gestures and contemporary realities.
Peat extraction, hemp cultivation and fishing in the Audomarois marsh
In addition to the market gardening activities entrusted to the brouckaillers, the Audomarois marsh has long allowed the development ofother economic activities.
In particular, the peat, used as fuel for domestic heating. Many current ponds, like that of Romelaere, are the remains of these old extraction areas.
The marsh also welcomed the hemp cultivation, intended for the manufacture of boat ropes.
The inhabitants, for their part, were alsoexcellent fishermen, inventive and ingenious.
Fishing techniques of yesteryear
If today only the angling is allowed (and only with a valid fishing license), it was quite different in the past.
At that time, various methods were used, often collective and clever, now banned:
la trap fishing or the family drum,
la fouenne, a trident planted in the fish,
many blots et bundles, eel traps,
la pouch and poisenette, artisanal landing nets.
These popular practices, passed down from generation to generation, are part of the living heritage of the marsh, although their use has disappeared.
Tuft fishing, a specialty of Audomarois
Before theEuropean eel Although it is not a protected species, the people of Audomar practiced a typical fishing style: tuft fishing.
It consisted of shake a ball of earthworms weighted with lead in the water, until an eel bit into it. Then it had to be to strike with a sharp blow, before she reflexively opened her mouth, then capture her in an upturned umbrella.
This ancestral gesture, now obsolete, bears witness to a detailed knowledge of animal behavior, and a intimate link between man and his marsh.
The traditional festivals of the Audomarois marshes
While some holidays have disappeared over time - such as the Lyzel procession, formerly composed of floats parading between the Clairmarais road and Saint-Martin Street in Saint-Omer — others continue to gather the crowds.
Two major events still make the hearts of Audomarois beat faster every summer:
Le nautical procession of the Haut-Pont, organized on last Sunday in JulyIn this emblematic suburb, the decorated boats parade on the water, to applause.
Le August 15 boat pilgrimage, towards a statue of the Virgin located at the intersection of Large Large and Écou Riveror a TilquesThis spiritual and popular moment combines contemplation and attachment to the marsh.
The town of Saint-Omer also maintains the tradition of northern giants carried.
Batistin, central figure, represents a gardener of the Bachelin marsh.
He is accompanied by his companion Belle-Lyze.
Like popular mascot, Batistin gave his name to several local projects, witnesses to the liveliness of this figure in Audomarois culture:
– A cheese produced by the Milou farm in Tatinghem
– A bacôve of the Maison du Marais
– A gîte de France in St Omer, at the gateway to the Audomarois marsh
– A shared garden in the heart of the city
A walk in the marshes of Saint-Omer and Clairmarais
Le best way to discover the marshes of Saint-Omer and Clairmarais remains without a doubt the a boat.
On board a follow or traditional bacôve, last boat makers invite you to a walk along the water, between peaceful rivers, cultivated plots et wildlife. A journey exotic and authentic, in the heart of a landscape shaped by man for centuries.
For lovers of land walks, the marsh also offers several farm roads, walking trails and hiking trails accessible on foot or by bike.
Among the most popular routes:
le Lansbergue trail, between Tilques et Serques,
and bowl path, connecting Clairmarais, Nieurlet et North Peene.
👉 Consult the complete booklet of hiking trails in Audomarois here (PDF)
Finally, the Romelaere nature reserve, a stone's throw from Clairmarais, offers a route of more than 2 km, marked and accessible to people with disabilities.
birdwatching posts mark the path, allowing you to discover:
many pollarded willows,
many wet meadows,
many old peat bogs, which became ponds,
and many species of birds, some of which are protected.
To enrich your visit, a free audio guide is available at the park entrance, at the Barn Nature, a reception and environmental awareness space.
Whether on the water, on foot or by bike, the Audomarois marsh is revealed with humility and majesty, as long as we take the time to listen to it.
