The EPTB Vilaine was created in 1961 between three counties in Brittany to manage the Vilaine river basin through flood prevention, developing farmland, and restoring navigation. It has since expanded its role to include water supply, environmental protection, and sustainable development. Key actions have included building the Arzal dam, operating a major water supply plant, and coordinating management across the basin through the SAGE planning process. Current issues center around balancing the needs of water supply, flood control, agriculture, navigation and the environment in a context of increasing water scarcity and usage conflicts. A major project under consideration is building a new lock at the Arzal dam to prevent saltwater intrusion while minimizing

1. EPTB Vilaine

4. An old story
With large activities…

5. IAV was created in 1961 between 3 counties :
Loire Atlantique, Morbihan, Ille et Vilaine
Vilaine marshes dynamic
Flood prevention
Develop new farmland
Restore navigation
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35
44
A tool to serve the counties

6. Goals quickly completed with water
supply (Férel plant was inaugurated in
1972) and later with maintenance of
the waterway (1989)

7. Some key dates
1961 à 1970
Building of the Arzal dam
1972
Water supply plant
1989
Concession of the waterway
1995
First « environmental contributions »
1998
IAV is designated as SAGE operator
2003
Official approval of SAGE Vilaine
2007
EPTB Vilaine
2010
Reviewing of Sage Vilaine

8. Status
Public Administrative Institution with legal
and financial autonomy
« Etablissement Public Territorial de
Bassin » (waterboard) of the Vilaine
catchment area since 2007
Board :
12 County Conselors (3x4)
1 chairman
2 vice-chairmen

9. Average budget :
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•
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Investment budget : 6/10 M€
Operating budget :
12/14 M€
Conties contributions + subsidies
45 Employees

10. Actions and issues

11. 1- Context/goals
Management of the water
reservoir : water supply,
navigation, flood prevention
Prevent the conjunction of
Vilaine flooding and high tide in
Redon
Arzal dam : keystone of
hydraulic regulation
Minor side hydraulic structures on
Isac et Trévelo

13. 2- Recent and ongoing actions
Maintenance of the waterway
Upgrades of the Arzal dam
Design of a new lock at the
Arzal dam (DROP project)
Original role:
Flood prevention
Development of
agriculture
Commercial navigation
Current role :
Main objectives :
Water supply and flood
prevention
Secondary objectives :
Navigation
Maintain a good balance in
the Vilaine estuary and
marshes
Fish migration

14. 3- Issues
Keep a high standard of
performance in water level
management
Equipments reliability
Make our management more
« visible » and
understandable for public and
users

15. 1- Context/goals
Complex environment with
frequents usage conflicts
Upsets induced by the dam
achievement
Siltage connected to « water
supply » usage
IAV is « in the heart of the
landscape »

16. 2- Recent and ongoing actions
Efficient dialogue within an
Estuary Steering Committee
Building of a ship designed
for specific dredging
operations
3D hydro-sedimentary and
hydro-dynamic modelling
Transfer of mussel culture
installations

17. 3- Issues
Think in terms of sustainable
development …
Work on social acceptance of
development operations
Weight the pros and cons
before embarking on
important dredging programs

18. 1- Context/goals
Founding and statutory mission
of IAV, enhanced by the SAGE
et EPTB status
Expertise at the whole
catchement area scale.
Coordination, assistance to
local organizations
Management of the structuring
projects.

19. 2- Recent and ongoing actions
Hydraulic modelling
Global understanding
Simulation of scenarios : local
protection, flood reservoirs,
structures management…
Reducing vulnerability
Risk Awareness
Put flood marks
Crisis management
Assistance to local
communities
Construction programs
Flooding areas (Chateaubriant)
Dike restauration (Moisdon)
InterReg programs : Wave

20. 3- Issues
Enhance risk awareness
Work on reducing
vulnerability
Develop cost/benefits
analysis for important
construction programs

21. 1- Context/goals
One of the 2 biggets plants in
Britanny : an average of 17
Mm3/year
Towards Morbihan
25%
Towards Ille et Vilaine
5%
Towards Loire Atlantique 70%
Key role of regional regulation
In winter : 30 000 m3/day
In summer : 90 000 m3/day

22. 2- Recent and ongoing actions
New contract of public service
delegation covering the period
2009/2023
Restructuration of the plant to
enhance the process (COT,
micropollutants) : 2016/2020
New feeder towards Rennes :
2017/2020

23. 3- Issues
Maintain the key role of
regional regulation
Improve the process to keep
the plant « up to date » and
to anticipate new
regulations/pollutants
Management of the reservoir
during periods of
drought/water scarcity

24. 1- Context/goals
European framework + EPTB
(Waterboard) status : key role
on water and aquatic
environments
Some remarkable aquatic
environments on the basin
Wetlands locally very important
for water quality
Vilaine is a major axis for fish
migration

25. 2 – Recent and ongoing actions
Monitoring of the Arzal dam
fishpass (strong eel expertise
on the basin)
Natura 2000 operator on the
Vilaine marshes : write the
targets document
Coordination of the of rivers
and wetlands inventory at the
basin scale
Cartography of primrose – local
works of primrose uprooting

26. 3 – Issues
Keep a high level of expertise
Work on local acceptance of
glass eel fishery regulation
Improve the hydraulic
regulation of Vilaine marshes :
not only flood prevention and
water supply, but also
environment issues,
navigation… : Arzal dam
becoming a multi users
hydraulic structure

27. Context
Multi users area : water supply,
flood prevention, agriculutre,
navigation…
Current lock causes salt
intrusions penalizing water
supply
Siphons to prevent salt
intrusions : losses of huge
amounts of fresh water (300
000 m3/day)
Water scarcity :
-restrictions in the use of lock :
conflict with boaters
-Preventive rise in water levels
to increase the capacity of
storage : conflict with farmers

28. Project
New lock anti salt intrusions
No need of siphons to prevent
salt water intrusions : no
losses of fresh water
Water scarcity :
- No restrictions in the use of
lock : no conflicts with boaters
- No need of preventive rise in
water levels : no conflict with
farmers
Problems :
-Be sure of the efficiency of the
project
-Cost of the project : 20 M€

33. Institution d’ Aménagement de la Vilaine
EPTB Vilaine