E
cosystem
servicesdelivered
Provisioning
Regulation & maintenance
Cultural
Abiotic
C
ontribution
topolicyobjectives
Water Framework Directive
Floods Directive
Birds & Habitats Directive
2020 Biodiversity Strategy
P
otential
biophysicaleffects
Runoff
Reducing pollution
Soil conservation
Habitat
Climate Change
High
Low
Medium
None
Removal of longitudinal barriers restores
river continuity
, de-fragments stream
habitats
and improves their quality. This contributes to improving the status of hydromor-
phology quality elements and to improving ecological status by providing
increased diversity
of (migratory) fish and other aquatic communities (such as benthic invertebrates
and macrophytes). Along with improving the conditions for seasonal fish
migration and reproduction
, these effects significantly contribute to addressing Habitats and Birds
Directives and 2020 Biodiversity Strategy.
The measure also results in the restoration of the natural pattern of erosion, sediment transport and deposition, which may result in increased erosion and sediment delivery
downstream.
Impacts on flood risk reduction can be
controversial
. On the one hand, dams and weirs are built as flood protection measures, in which case their removal might be expected
to increase flood risk. However in some cases their removal prevents the risks of accidents during floods. This needs to be considered on a case-by-case basis.
Potentially the restoration of river continuity may also improve navigation conditions.
If removal is found not to be possible, many dams and weirs are suitable for reconstruction with addition of small hydropower facilities and fish passages, which provide abiotic
ecosystem services.
