Environmental Engineering Reference
In-Depth Information
defences, whilst the EU's Floods Directive (2007/60/
EC) aims to reduce fl ood risk in the context of human
health, the environment and cultural and economic
issues. However, in many countries, the scientifi c evi-
dence that new urban developments will not increase
fl ooding in vulnerable highly urbanized areas is still
not available. In continental Europe, the pressure not
to change traditional fl ood defence ways is exacer-
bated by the transboundary nature of rivers. Those
countries where the precautionary principle of highly
engineered rivers and fl ood defence systems is widely
applied are often at the downstream end of the river.
The Netherlands is just one example where the gov-
ernment has little control over what water is received
from the Rhine and Meuse. Whilst the River Basin
Management plans drawn up for the Water Frame-
work Directive potentially provide a more uniform
catchment-wide view to the management of the rivers
across country boundaries, it will take some time
before associated programmes of measures can all be
implemented, and until such time individual countries
will inevitably remain cautious about altering existing
approaches.
However, without reliable and complete estimates of
the
costs and benefi ts
of river restoration, much work is
undertaken on a piecemeal and opportunistic basis.
Directly comparing the cost of a road improvement
scheme and the value of fl oodplain woodland is still,
for example, very diffi cult. Legislation has assisted res-
toration objectives such as the EU Habitats Directive
92/43/EEC (EC 1992a) that requires member states to
protect rare habitats and improve to 'favourable condi-
tion' habitats supporting rare species. Similarly, in
England, the Wildlife and Countryside Act 1981 and
the Countryside and Rights of Way Act are examples
of acts which can encourage river restoration actions.
There are now moves to include cost-benefi t analyses
which focus on the services that ecosystems provide
rather than just actions to conserve specifi c species or
features. To date, inadequacies remain in the interpre-
tation of biodiversity, aesthetic, public enjoyment and
natural heritage issues in the ecosystem services
approach.
long - term
sustainability
of a project and meeting the
aspiration of
ecological restoration
, as defi ned by
the SER Primer (Society for Ecological Restoration
International (SER) 2004; see Chapter 2). The success
of a project will depend on the
reference
conditions
against which it is measured. Projects have to consider
how conditions at a site relate to not only the historical
attributes but also the contemporary and future
context. Therefore, a variety of integrated elements
(see Figure 17.1) and needs have to be considered on
their own merits. It is not simply about putting things
back to the way they were a number of years ago. In
some cases, a previously straightened reach may be
restored to a meandering form (see Figure 17.2) bring-
ing with it the added benefi ts of increased biodiversity,
but this is by no means always the most appropriate
method. The recovery of an ecosystem may, for
example, be assisted by smaller scale restoration prin-
ciples, such as re-profi ling river banks and creating wet
berms to rehabilitate habitat and re-invigorate natural
processes along existing river sections (Figure 17.3).
The following section provides some examples of the
types of issues impacting on rivers and fl oodplains and
also outlines those factors that are driving river resto-
ration in various countries across Europe. The follow-
ing examples are by no means comprehensive and
many more examples can be found in other textbooks
(including Ward
et al
. 1993 ; Middelkoop & van Haselen
1999 ; Klijn & Dijkman 2001 ; Nijland & Cals 2001 )
and the River Restoration Centre's (RRC)
Manual of
Techniques
(RRC 2002 ).
United Kingdom
In the United Kingdom, rivers have been substantially
altered over the past few centuries, with at least 80%
of lowland river reaches having had at least part of
their channel modifi ed (Raven
et al
. 1998 ). Degra-
dation has been particularly severe in the last 50
years through intensive management. Programmes of
draining, dredging and straightening have altered
almost all rivers. Since 1990, various groups and gov-
ernment agencies have been working to change the
perception of river managers and to promote a more
sustainable approach to river and fl oodplain use and
river management, rather than purely as fl ood defence
drivers.
In the 1980s, conservation and river enhancement
was restricted to voluntary bodies and was seen as an
'add-on' to works under the statutory duties of fl ood
17.4.2 European River Restoration
in action
There is no simple solution to restoring and rehabilitat-
ing rivers and their fl oodplains, particularly in terms of
