Geoscience Reference
In-Depth Information
turn vision into reality; (iii) to provide a focus
for developments and planning activities of various
regional and local organizations - a script for joint
activities; (iv) to demonstrate the details of various
options; and (v) to invite potential partners to
cooperate in the work. The Plan is refined and
updated as opportunities and needs arise.
system. The main ecological objective is to
enable the development of floodplain meadows.
Beyond the channel, re-development of floodplain
habitats sustained by rain water and streams will
supplement the ecological recovery. In densely
populated
areas
where
space
is
very
limited,
the
river
profile
must
be
adapted
within
the
constraining factors.
The concept is therefore a model that can
define the optimum ecological design for waterway
recovery (Plate 24). It is based on four principles:
(i)
a
Ecological concept
non-interrupted
river,
as
far
as
possible,
An underlying principle of the
Masterplan
Emscher:future
was an ecological concept for
the Emscher River (Semrau
et al
., 2009). Other
components were related to flood management,
groundwater management, urban development
and leisure opportunities. Because of extensive
physical alteration, the Emscher and its tributaries
bear no resemblance to the river or support the
aquatic and floodplain ecosystems of the pre-
industrial catchment landscape that existed more
than 150 years ago. The 'reference condition'
(
sensu
WFD) for the Emscher is a lowland sand-bed
river (cf. LAWA, 2000). Feasibility studies quickly
showed that the consequences of coal mining,
industrial development, population changes and
the severe physical degradation of the channel
would prevent pre-industrial river conditions being
restored. It was simply not possible to return the
river to its original, meandering state. In these
circumstances, reference conditions could not be
the direct goal for river rehabilitation, but they
provide useful guidance on the most appropriate
type of actions to achieve 'good ecological potential'
for heavily modified watercourses, as required by
the WFD.
The spatial planning approach to rehabilitation
was based on the availability of space alongside the
river channel. In some locations sufficient space
should enable an 'assisted natural recovery' of
the Emscher river-bed (Newson, 2002; Kondolf,
this volume), allowing development of features
and vegetation typical of a lowland river and
its floodplain. These localities, together with
confluences where less heavily degraded tributaries
join
connecting source to mouth;
(ii)
'ecological hot spots' are the most important
locations for ecological development of the river
- these locations allow the Emscher to shape
its channel and floodplain in a near-natural
fashion and provide opportunities for features and
vegetation typical of a lowland river to develop;
(iii)
the confluence points of relatively unaffected
tributaries are important nodes in the river system,
because they are sources of recolonization by flora
and fauna;
(iv)
adapted urban wetlands provide the chance
for floodplain-related habitats to be developed
behind flood embankments, providing further
biological connections with the water-related and
other biotopes in the catchment.
Creating an ecological hotspot
- Emschermouth
One of the major ecological 'hot spots' to be
developed will be re-creation of the Emschermouth
(Plate 25). This is where the river joins the Rhine
and is the location of the redundant centralized
wastewater treatment plant. Regeneration of the
site will form a new mouth area of about 19 ha.
Work will include installing five rock ramps in
the channel to overcome the difference in river-
bed height between the Rhine and Emscher caused
by previous river management to counteract
subsidence from coal mining. More than 2 000 000
m
3
of soil will be excavated and half of this used
to construct embankments. Similar to the Rhine
floodplains, the new Emschermouth will usually
the
main
river,
will
provide
'nodes'
for
flora
and
fauna
to
recolonize
the
waterway
