Geoscience Reference
In-Depth Information
CHAPTER 19
Multi-Purpose, Interlinked and
Without Barriers: The Emscher River
Ecological Concept
Mechthild Semrau and Rudolf Hurck
Emschergenossenschaft, Essen, Germany
Introduction
density (2 700 km 2 ) is one of the highest in Europe
and 30% of the catchment area has an impervious
surface (Sieker et al ., 2006).
To accommodate major industrial development
in the catchment, the original meandering river
and its tributaries were systematically engineered
from the early 1900s to form what was effectively
an open wastewater sewer system. Construction
of closed sewers was prevented by frequent large-
scale ground subsidence caused by coal mining
in the area. Sewage was processed centrally at
a water treatment plant at the confluence with
the Rhine. To counteract the effects of mining
subsidence, the river bed along 82 km of the
channelwasloweredbyupto9m;thiswork
was augmented by flood embankments up to
10 m high along 75 km of the lower reaches.
Most of the tributaries were engineered in similar
fashion. In many places, industry developed on
land immediately adjacent to the river channel.
A major part of the catchment was turned into
polder and the landscape developed into a multi-
structured pattern of urban areas alternating with
grassland, woodland and agriculture. In the early
1990s mining activities moved away from the
Emscher area. At the same time the existing
drainage system was no longer able to comply with
stricter wastewater treatment and water quality
nutrient standards. Consequently, transportation
River restoration and rehabilitation work over the
past 20 years has largely been carried out at the
site level ( Aberg and Tapsell, this volume; Holmes
and Janes, this volume), and there are very few
examples where it has incorporated an entire river
catchment. The Emscher region in Germany is
such an example; water quality improvement and
river rehabilitation are core elements of a major
30-year economic regeneration and environmental
improvement programme for a former heavily
industrialized catchment. This chapter provides a
brief overview of the effects of industrial growth,
the spatial planning and ecological concepts behind
the regeneration programme, the institutional
structures that have enabled the work to be carried
out, the design of an 'ecological hotspot' and some
results from the first 20 years.
The Emscher River
The Emscher River and its tributaries are 340 km
in length and together drain a catchment area of
865 km 2 before joining the River Rhine in the Ruhr
region of north-west Germany. With 2 300 000
people living in the catchment, the population
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