The Mourachonne: Grasse’s significant river

Small rivers and streams, even in the countryside, are often forgotten today. Many of them have been tidied up, culverted or piped to within an inch of their existence. That is, until unanticipated rainfall occasionally causes disaster (for example when the river Brague burst its banks in 2015 and killed several occupants of a residential home).

Grasse’s most significant river, the Mourachonne, is one of these generally unnoticed streams. It rises in obscurity from a gap in a steep hill side, flows rapidly and unobtrusively downhill and feeds some of Grasse’s most important surviving flower fields as it reaches the valley floor. Then by joining with its main tributary, the Riou Blanquet, it has created the land where many of Grasse’s modern perfume factories are located, culminating in the flood plain around Le Plan de Grasse, across which it would once have meandered.

Hidden for most of its course, its value on the one hand and hazards on the other are typical of modern waterways.

The river’s source and its upper valley

France’s Eaufrance official public information service on the country’s waters classifies the stream as the Mourachonne right from its source, even though IGN maps use the name ‘Grand Vallon’ for its upper reaches.

Upper course of the Mourachonne. Source: Géoportail (www.geoportail.gouv.fr) IGN and Reseau Hydrographic

The Mourachonne exits the hillside just above the pretty Placette St Antoine in the Roumégons quarter of Chateauneuf de Grasse, and according to Eaufrance, it’s 14km long up to its confluence with the Siagne river at Pegomas.

It flows sharply downhill at first towards the bottom of the Malbosc domain and the St Jean quarter. It’s possible to reach it via paths and tracks and to see that apart from the occasional bridge, its natural course has never changed.

It is in the St Jean quarter, when it is joined by several smaller streams, where it starts to become significant to Grasse. It marks the start of what was once a huge area for growing centifolia roses and tuberoses. At that time, all the perfumeries which processed the flowers were located in and near the old town, away from the valuable flatter cultivated land. The Napoleonic cadastre (land registry) shows parcels labelled ‘roseraie’ or ’terre à fleurs’ dominating the land usage all the way to Le Plan and beyond.

Even today, the St Jean area remains important for flower growing, especially for high quality roses. Lancome’s Domaine de la Rose is here, while above it on the eastern valley side is DSM-Firmenich’s Villa Botanica. Another experimental rose field is run by Laboratoire Monique Rémy, a local subsidiary of International Flavors and Fragrances which specialises in natural essences.

(Top left) The source of the Mourachonne at Chateauneuf. Almost all rivers start in deep obscurity. (Bottom left) The LMR experimental rose field, The river is on the far side and HG Wells' house 'Le Pidou' peeps through the trees behind. (Right) The stream is deeply incised near the Domaine de la Rose.

A managed watercourse

Below the flower fields, the river becomes more deeply incised and its course has been controlled to allow housing and other development. Both the railway to Cannes (completed in 1871) and the Canal de la Siagne (opened in 1868) cross the river. The river passes through a tunnel built into the embankment of the railway and the canal flies high above it on an aqueduct.

(Above) The Mourachonne runs through the railway embankment. The railway engineers were taking no chances with the river: the tunnel is large. (Below) The Canal de la Siagne soars 40 metres over the river.

Even so, the stream appears fairly natural. That changes abruptly by the time it reaches its confluence with the Riou Blanquet, at what is now the Moulin de Brun roundabout. Once, its course would have started to meander, creating the flat area around the hamlet of Le Plan. But instead of flowing quietly and obscurely down the valley, it enters a deep and obviously human-made incision intended to control its course to allow development of the land.

Lower course of the Mourachonne (source: Google Earth)

The takeover of the perfume fields

This luminous photo from the Jean Luce collection (Archives of the Alpes-Maritime in Nice) shows the Mourachonne valley in about 1905 when it was almost entirely agricultural and contained extensive flower fields.

After the second war, it became logical for the fragrance and flavour industry to develop new sites directly on this controlled flood plain. Their materials sources were moving from local to imports, and flatter land allowed the creation of more modern, chemicals-orientated factories. Public transport also improved labour mobility. And when a business needed more factory space, it could sometimes use plantation land which it already owned.

Bertrand Freres developed what is now the abandoned Biolandes site near Moulin de Brun as early as the 1920s. Robertet found that even its large site on av Sidi-Brahim was insufficient for its needs and commissioned its new factory on Le Plan in 1982.

Approximately the same view today, although the quality of the image is much poorer. There is still a surprising amount of green space, but the development along the valley can be seen stretching from the centre of the photograph below the town and towards the right.

The dangers of human interference

As almost everywhere with waterways, human interference hasn’t been 100% effective. Surveyors and hydrographers have something of a track record of optimism about the effectiveness of their attempts to control nature. The Mourachonne is no exception.

Eaufrance officially classified the area as ‘inondable’ (‘flood prone’) and in 2009 extensive works were carried out to avert flooding, including a measurement and warning site near the Moulin de Brun.

The Mourachonne at Le Plan de Grasse, looking quite innocent on an autumn day, but note how human interference has created a deep channel. (Bottom right) The old bridge at Le Plan.

Since development close to the river has recently restarted, these flood prevention measures seem to have worked, although perhaps at a cost to Pegomas downstream on the river. You can see what happened there as recently as October 2024:

New developments

The flood prevention measures seem to have given new impetus to factory development near the river. Givaudan is to re-develop the derelict Biolandes site for its ‘House of Naturals’ business (more details here). Just along the road Cosmo International Fragrances is building a new factory on the site of old flower fields which were recently part of a commercial nursery. A little closer to Le Plan, a new board has also just gone up announcing a new building, on a very similar site, for Payan & Bertrand, a historic Grasse business which has apparently run short of space at its premises on av Jean XXIII.

I hope that the hydrologists and engineers have got it right this time!