Re-activation of the fluvial dynamics of the Rhone river ... · Re-activation of the fluvial dynamics of the Rhone river, from complete harnessing back to channel shifting procedures

Re-activation of the fluvial

dynamics of the Rhone river,

from complete harnessing back

to channel shifting procedures

Atelier de géomorphologie fluviale Gaydou, le 8 Juin 2011

The Rhone

river

National Rhone Company

Harnessing the Rhone river (18-19th century)

• 1860 : farmer’s or trade’s dikes

Potential

sensitivity to

flooding and

sedimentation

• 1880-1920 : Girardon’s dykes

Harnessing the Rhone river (1880-1920)

The 1878 law declares Rhone’s improvements works as public utility. Almost

all the Rhone river course is harnessed, in majority downstream of Lyon.

78% of the « vieux Rhone » length is harnessed (between 45 et 100%)

The aim is to improve navigation conditions : stabilization of channel course,

concentration of fluxes in a unique arm, increase channel depth, turn

dangerous sections (cross riffles) into safer by changing the riffles orientation

Girardon dikes building,

Collection Dürrenmatt -MDFR

Harnessing the Rhone river (1840-1986)• 1890-1920 : Girardon’s dikes principle

Harnessing the Rhone river (1880-1920)• 1890-1920 : Girardon’s dikes impacts

Collection Dürrenmatt, MDFR

• 1952-1980 : NRC dikes

Harnessing the Rhone river (1948-1986)

National Rhone Company

Impacts of the two generations of civil engineering

works :- Channel has no more lateral mobility

- The topographic level of the river margins raised

-The bypassed discharge decreased

The Rhone river conditions :

-The changing of softwood forest into hardwood forest

- The side arms’s number and depth decreased

-The water level worsening during flood

- The alluvial ecosystems disappeared

The dams constructions on the tributaries, the erosion decreasing and the

sediments extractions induce fine sediments decreasing in the Rhone channel

while sediment balance is positive on the margins.

Gaydou, 2009

More room for the Rhone river

Directory scheme methodology

Works phase applied to Pont-Saint-Esprit

Girardon dike and

groynes

Submersible dyke

National Rhone Company,

2010

0

100

200

300

400

500

600

700

800

900

1000

24-Sep 24-Oct 23-Nov 23-Dec 22-Jan 21-Feb 23-Mar 22-Apr 22-May 21-Jun 21-Jul 20-Aug 19-Sep

Dail

y F

low

(m

3/s

)

First results

National Rhone Company,

2010

Merci de votre attention

Dessins de Mix et Remix, troisième correction du Rhône