River (France) and biology: example of the Vienne Influence of dam removal and past sediment mining on river morphology

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Influence of dam removal and past sediment mining on river morphology

and biology: example of the Vienne River (France)

S. Rodrigues, N. Richard, P. Juge, J. Berthomé, G.

Cochet, J.R. Malavoi

Université François Rabelais de Tours, CNRS/INSU - UMR 6113 CETU Elmis

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Context

Due to the Water Framework Directive, dam removal is going on in France

Free migration of sediments and fish Space and mobility for rivers

Masterplan « Plan Loire Grandeur Nature III »

River incision problems

Lane's Balance (after E. W. Lane, from W. Borland)

Morphological equilibrium

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After Andriamahefa, 1999, modified. Data : MNT USGS, mesh 1 km x 1 km

A tributary of the Loire: the Vienne River

Catchment area of the Vienne River: 21 000 km²

Stream length 370 km

< 35 m 35-60 m 60-75 m 75-115 m 115-155 m 155-200 m 200-300 m 300-500 m 500-1000 m

> 1000 m 0 100 km

Belleville/Loire Dampière en Burly

Loire River: larger french river Removal of several dams

Context and study site

REMOVAL OF MAISONS-ROUGES’ DAM

Dam of Maisons Rouges on the Vienne River

(removed in 1999)

Dams removed

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Dam Study site and dam features

Before removal

• Confluence Vienne - Creuse

• 4 m high, 200 m in width

• built in 1922

• 900 000 m³ of sediments trapped upstream

• removed in 1999

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Questions, goals and approach

• Ability of the river to flush the sediment downstream and restore a morphological equilibrium

• Influence on in-channel species in the dam and

downstream (benthic macroinvertebrates, mussels…)

10 years sedimentological and morphological survey Analysis of habitat diversity and populations

(vegetation, benthic macroinvertebrates, mussels) Questions

Approach

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• Bed topography in 1998, 1999, 2000 a and b, 2002, 2005, 2009 (226 cross sections; less than 200 m on average)

• Grain size analysis of bed sediments

• Aerial photographs (constant discharge)

• Analysis of vegetation, macroinvertebrates and mussels

0 500 1000 1500 2000

28/10/1995 24/07/1998 19/04/2001 14/01/2004 10/10/2006 06/07/2009 01/04/2012

Approach: physical and biological survey

Discharge (m³/s^-1)

Removal of the dam

Q₂ Q₅ Surveys

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Sedimentological and

morphological survey

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Results: downstream migration of sediment waves

• Significant upstream scouring since dam removal

Just upstream the dam

6 km upstream

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Dam

•1999

•2000a

•2000b

•2002

•2005

•2009

Sediment deposition downstream the dam and migration of large bars at a velocity of 2.5 km/year

10 km downstream dam

Results: downstream migration of sediment waves

Bar deposition

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T₀ T₁ -

Fill Scour

Distance from left bank (m) Elevation (m)

T₀

T₁

Cross section analysis

Results: sediment budgets between 2005 - 2009

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Preferential sites for sediment deposition?

EVOLUTION DES FONDS ENTRE 2005 ET 2009 SUR LA VIENNE ET LA CREUSE Bilan sédimentaire Vienne et Creuse confondues

-140000 -120000 -100000 -80000 -60000 -40000 -20000 0 20000 40000 60000

15 20 25 30 35 40 45 50 55 60

PK (distance à la confluence avec la Loire)

Différence de section (m2)

Repères Vienne et Creuse 05-09

l'Ile Trogues Pouzay Nouâtre Ancien barrage Les Ormes Chezelet

Briançon

Scour

By passing Fill

Creuse

Results: cumulative sediment budgets between 2005 - 2009

Dam

Distance from the Loire (km) Cumulative

volume (m³)

Flow

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Alt. NGF (m)

t

₀

= rgR

_h

sinf (sinf = f)

LIGNE D'EAU DE LA VIENNE, PENTE ET FORCES TRACTRICES ASSOCIEES (2009, environ 100 m ³.s ^-1à Nouatre )

28 29 30 31 32 33 34 35 36 37

15 20 25 30 35 40 45 50 55 60

cote NGF

Altitude plan d'eau 2009 Repère

Alti 2005 l'Ile Bouchard Trogues Pouzay Nouâtre

Ancien barrage

Les Ormes Chézelet

Briançon

0.48 o/oo 10,8 N/m²

1,08o/oo 25,3 N/m² 0.15 o/oo

3,1 N/m² 0.05 o/oo

1,3 N/m²

0.10 o/oo 2,4 N/m²

1,08 o/oo 24,6 N/m²

Results: bed shear stress assessed from water levels

Scour By-passing Fill

Distance from the Loire (km)

Dam

Combined effect of dam removal and past sediment mining?

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0 10 20 30 40 50 60 70 80 90 100

10 15 20 25 30 35 40 45 50 55 60

Pk (distance confluence à la Loire, km) Force tractrice critique (N.m-2 ) tc pour D90 (points)

t générale pour 100 m³.s^-1 à Nouatre (droite)

0 5 10 15 20 25 30

10 15 20 25 30 35 40 45 50 55 60

Pk (distance confluence à la Loire, km) Force tractrice critique (N.m-2 ) tc pour D₅₀(points)

t générale pour 100 m³.s^-1 à Nouatre (droite)

r 

r t



_c⁼₍ _s_ _w^c ₎_g_._D⁼^fct^u^*^D

Shear force Gravity force

 =

Threshold of motion for a given grain size REMOVAL OF MAISONS-ROUGES’ DAM

Results: sediments mobility

Critical bed shear stress (assessed from D₉₀)

Bed shear stress (for Q = 100 m³/s^-1 at Nouatre*)

Critical bed shear stress (assessed from D₅₀)

Bed shear stress (for Q = 100 m³/s^-1 at Nouatre*)

Distance from the Loire (km) Shear stress (N.m^-2)

*Q = 100 m³/s^-1 at Nouatre is reached 60% of time

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Biological survey

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Margaritifera auricularia

Length : 20 cm

Life duration : 150 years Habitat : stabilized gravels

Status : protected by IUCN, protected in France,…

Rediscovered in the Vienne in 1998

Results: influence of dam removal on Margaritifera auricularia

Endangered specie

- Small and old populations (recruitment?), - needs fish for reproduction (which ones?)

- sensitive to river degradation (fine sediments…)

Were the populations of Margaritifera

auricularia affected by the migration of bedload sediment waves coming from the dam?

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Dam

1999 2000a 2000b 2002 2005

2009

4 stations were surveyed

- Bed topography (cross sections spaced 10 m on average)

- geolocation GPS and tagging

Influence of dam removal on Margaritifera auricularia

1 2

3

4

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-Pertes les plus importantes au niveau des zones courantes (station de l’A10 et de Mougon)

-Trouvées quand sur les stations de Chinon et A10?

Barres sédimentaires en 1999

Results: influence of dam removal on Margaritifera auricularia

2002: 283 mussels 2009: more than 90 mussels disapeared (1/3 of the population)

0 20 40 60 80 100 120

Sation 1 Sation 2 Sation 3 Sation 4

2002 2009

-30 -25 -20 -15 -10 -5 0 5 10 15

Sation 1 Sation 2 Sation 3 Sation 4

Difference 2002-2009 Dam

Dam

Number of mussels Number of mussels

Small increase upstream (habitat)

Significant decrease downstream

Flow

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V029

Left bank

Is the decrease of mussels due to sediment transport?

Results: influence of dam removal on Margaritifera auricularia

Mussels populations were mainly located near the banks (30 m) - Not due to burying because mussels were present in 2002 and bedload waves migrated in 1999 in this part of the river…

Hypothesis:

- Erosional context induced by dam removal ? - Spawning areas of Petromyzon marinus?

Ex. of station 2

Mussels (30 in 2002, 4 in 2009)

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Conclusion and Perspectives

In 10 years, large bedload waves migrated 27 km downstream of the dam (celerity of 2.5 km/year)

Sediment trapping occured in the abandonned sediment mining sites

Detailled topographical surveys at past sediment mining sites

Regressive erosion is due to dam removal but also probably past sediment mining (stopped in 1998)

Study of bedrock outcrops and lateral migration of the river

Margaritifera auricularia was found in the Vienne in 1998 but the populations are decreasing (excepted upstream of the dam).

Topographical survey and tagging, influence of Petromyzon,…

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Thank you for your attention

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PROFIL LONGITUDINAL DE LA VIENNE ET LA CREUSE Points durs

24 25 26 27 28 29 30 31 32 33 34 35 36

15 20 25 30 35 40 45 50 55 60

altitude NGF du talweg

Creuse Vienne Points durs

Will the river incise its bed ?

Results: bed shear stress assessed from water levels

Distance from the Loire (km)

Possible vertical scouring

Bedrock outcrops

Scour By-passing Fill