Rigole d'Hilvern

An integral part of the Nantes-Brest Canal, this "artificial watercourse" brought water from upstream on the Oust to the Bosméléac dam, geographically the highest point on the canal, in order to maintain a constant level in the Hilvern sharing reach for smooth river navigation.

10 years of construction and a remarkable feat of engineering!

Between 1828 and 1838, men, women and children with picks, shovels and wheelbarrows moved millions of cubic meters of earth and stones to dig, earthen, level and level this channel over a length of 6,551 meters and 30 centimeters.

The Rigole d'Hilvern required a great deal of prowess and ingenuity to create this truly technical work of art. With a regular slope of 0.3 mm per metre, the Hilvern channel follows a furtive, life-size contour, with a 45-degree slope, a 1.20-metre opening at the base and an average depth of 1.20 metres.

This aqueduct enabled the hamlet of Hilvern to deliver 30 to 33,000 M3 of water in 24 hours. To waterproof the channel, a clay lining was carefully applied to the bottom of the trench, and in the meanders, more exposed to the friction of the water, an assembly of cut dry stones was sealed with mortar and lime.

The cuttings were used as backfill to create the embankments along the banks and the three-meter-wide service road. Each side of the Rigole was then lined with trees (beech, chestnut, maple, plane, poplar, elm) to reduce bank erosion and reduce evaporation of the water conveyed.

The rigole, reborn with the greenway.

This unusual work of art, now "dry", is an excellent cordon for exploring inland Brittany on foot, horseback or mountain bike, using the towpath rehabilitated as a voie verte (V8). This greenway allows you to discover the exceptional sites of the rigole à Trogardé in Merléac (B2), the Ponteur in Le Quillio (B2), the Pestuan trench in Saint Caradec (B3), the butte d?Hirgouët in Hémonstoir and Hilvern (B3), the bief de partage des eaux du canal de Nantes à Brest between the Blavet and Oust valleys.