August 30, 2016

Canal du Midi Designated as International Historic Civil Engineering Landmark

The plaque designating the Canal du Midi in France as an International Historic Civil Engineering Landmark (IHCEL) will be installed and unveiled at a ceremony in Naurouze, France, on September 8. The designation, recommended by ASCE’s Committee on History and Heritage, was approved by the Society’s Board of Directors in July. The nomination was co-sponsored by Societe des Ingenieurs et Scientifiques de France (IESF), the French organization of engineers and scientists. The canal was authorized by King Louis XIV in 1661 as an “in-country” water route from the Mediterranean coast of France to the Atlantic Ocean. Work on the canal began in 1667 under the direction of Pierre-Paul Riquet, Francois Andreossy, and Pierre Campmas. Fourteen years later the canal was opened for commercial traffic.

The canal is 150 miles (240 kilometers) long with a bottom width averaging about 36 feet (11 meters) and an average surface width of about 66 feet (20 meters). Originally there were 102 oval locks between the eastern end of the canal at the Mediterranean Sea and its western end at the Garonne River near Toulouse. It crossed the divide between the Atlantic and Mediterranean watersheds at an elevation of 620 feet (190 meters). The placement of the IHCEL plaque will take place in a ceremony celebrating the 350th anniversary of King Louis XIV’s edict authorizing construction of the canal. A delegation of nine persons will represent ASCE at the ceremony.

Water for the operation of the canal was provided by an ingenious system of collection and distribution channels used to collect flow diverted from streams flowing to the Mediterranean and convey it to a storage reservoir at St. Ferreol on the Laudot River – the largest man-made reservoir in the world at the time – formed by construction of the largest dam in the world. The distribution channels then conveyed releases from the reservoir to a basin adjacent to the canal where the water could be released to the canal in either the Mediterranean or Atlantic direction as needed. Water levels in the canal itself were controlled by the construction of berms along the uphill side of the canal to divert local runoff from entering the canal and by spillways on the downhill side at a number of locations along the canal to discharge excess water from the canal into local surface streams.

In addition to the historic water management aspects of the canal, there are several other features that merit recognition. Near Beziers, close to the east end of the canal, there is an eight-lock staircase excavated from solid rock that raises or lowers canal traffic 78 feet (25 meters) within a horizontal distance of about 1000 feet (300 meters). It is still the largest such staircase in the world. Just a few miles west of the eight-lock staircase the canal passes through a tunnel, excavated through a mountain at Malpas. The tunnel was blasted through a friable rock using explosives to create an opening 572 feet (173 meters) long, 21 feet (6 meters) high, and 28 feet (8.5 meters) wide to carry the canal and two towpaths through the mountain. It was the first tunnel in the world to convey a navigable waterway and the first use of explosives for civil construction on that scale. Another one-of-a-kind feature of the project was the construction of a round lock with three gates. The three gates were needed for through traffic on the canal and for maintaining access to an existing Mediterranean port south of the canal at Agde. The round lock was needed to provide sufficient space for tows desiring to turn to enter the canal from Agde or to exit the canal to Agde.

In addition to the canal itself, during the 14-year construction period the builders constructed seven large aqueduct bridges to carry the canal over surface streams and adjacent flood plains, 55 smaller aqueducts to convey surface streams under the canal and over 130 bridges to carry existing roads over the canal, More than 12,000 workers were employed in construction of the canal, bridges and aqueducts.

Within 20 years after the canal was opened to commercial traffic, the great French engineer Sebastien Vauban was hired to improve water management facilities by expanding some of the spillways and creating a tunnel to enable water from the collector channels to flow directly into the reservoir at St. Ferreol. Also, more than 45,000 trees were planted along the canal to reduce bank erosion and provide a canopy that would reduce evaporation losses from the canal surface. Although commercial traffic ended many years ago, the canal has proven to be a tremendous recreational resource generating more than $100 million annually from recreation boaters and hikers and bicyclists that use its towpaths. The canal is maintained by Voies Navigables de  France (VNF) the French government navigation agency.

A nine-person delegation will represent ASCE at the plaque placement ceremony organized by VNF. The plaque will be placed adjacent to a plaque placed in Naurouze in 2009 to commemorate Thomas Jefferson’s travel along the Canal du Midi in 1787 during his term of service as the United States Ambassador to France.

Thank you Augustine J. Fredrich, P.E., D.WRE, F.ASCE and Jerry R. Rogers, Ph.D., P.E., D.WRE, Dist.M.ASCE for preparing this announcement.