Supporting Technical Paper 3.
of biological and landscape diversity in the development of navigable waterways
by Mr. Gijs Kurstjens, Wissel Consultancy, The Netherlands
In this study
the effects of navigable waterways on landscape and biodiversity are presented.
Two types of navigable waterways are distinguished: canals and regulated rivers.
and positive effects of both types of waterways
construction of canals (mainly in the past) has caused great loss of natural
biotopes and a big barrier problem in the area being traversed. The problems are
very similar to the ones caused by motorways and high speed trains. Besides this
canals can have severe hydrologic effects (drying up of natural floodplains and
marshlands) and negative effects on native species (by connecting separated catchments and giving opportunities for exotic species to invade new areas).
canals have little variation in biotopes but in some sections new, sometimes
exceptional nature values have developed. In regulated rivers a large variation
of biotopes and populations can occur depending on the degree of regulation. The
measures for normalization and canalisation can cause severe negative effects on
the natural morphology and hydrology of river ecosystems as well as on natural
biotopes for the typical flora and fauna of floodplains. The worst effects are
caused by dams changing rivers into nearly standstill canals and a chain of oblong
lakes hardly passable for aquatic organisms.
to solve the negative effects
rivers can be restored with the natural river in mind. Morphologic and
hydrologic processes play an important role in natural rivers as well as biotic
processes. For instance flooding and the occurrence of alluvial forest are
typical for rivers. In dammed rivers streaming side channels can be constructed
around dams as fish passage and biotope for rheophile species. In normalized
rivers without dams old side channels can become alive by stimulating
morphological processes or active digging out by man. In many places stony bank
protection can be replaced by natural spontaneously grown alluvial forest with
exception of locations where navigable problems can occur (in river bends) and
bottle-necks in the river bed where problems can occur during floods.
Proposals of measures to ensure protection of biological and landscape diversity in future
In the case
of canals possibilities to compensate for negative barrier effects of canals
which fragment core areas of the Pan-European Ecological Network should be
investigated. On the other hand management authorities for waterways should
introduce ‘natural management’ along canals to gain a lot of ecological
benefit and landscape improvement. In case authorities are planning to build a
new canal it should be compulsory to carry out an impact assessment study as is
the case with new motorways and railways. This legislation does not exist
sufficiently in many countries outside the E.U..
assessment studies for large-scale regulation works (dams and locks) in rivers
should be made obliged by national law in all member states of the Council of
Europe. Attention should be paid to conflicting laws existing in some countries.
The legislation should be adjusted in order that both the barrier effect and the
loss of (flowing) aquatic habitats due to dam construction should be
Governments should put more efforts on the large-scale restoration of regulated river systems and emphasize measures based on the natural reference of particular rivers. For instance it is preferred to construct natural side channels in stead of fish passages to compensate for the barrier effect caused by dams. Financial means for restoration and nature development can be generated to combine measures for navigation with measures for safety, extraction of drinking water and tourism.