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History of Isar Renaturisation

Only geometry and functionality can beautify rivers

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Johann Tulla: "Every river or stream needs only ne bed, and if it has several arms, one should work towards a narrowed stream. It should be kept as straight as possible." (Vischer, 2000).
 

Isar stream in 1808 (red) compared to 1991 (green) on the right and to 2011 (blue) on the left

The Conflict: “Concretization” versus “Renaturalization”

 


The southern part of the Isar from the Großhesseloher Bridge to the Eisenbahn Bridge, was transformed by the City of Munich and the Bavarian Water Board without design competition nor broad public discussion.

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Motivated to pursue a more sensitive transformation of the Isar further downstream, the City of Munich and the Bavarian Water Board lanced a landscape design competition for the 1.6 kilometre stretch between Eisenbahn Bridge and the Museum Island.

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The first prize proposed keeping the linear character of the main stream while the second prize was awarded to a much more re-naturalisation-orientated attend.

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A heated discussion started around the two projects which grew into a public quarrel, opposing supporters of an urban, functional, and “honest” design, to supporters of a full renaturalization. Public meetings were held in the neighboring districts, where an active part of the population rejected the winning design for its consciously
built character and its linearity. The design was depicted as “banal” and some baptized the central pier/levee “the concrete monster.”

Isar competition, 2003-2005: first prize (Burckhardt/SKI), second prize (Jerney/EDR), final compromise (Burckhardt/Jerney/SKI) (State of Bavaria and City of Munich)

What is nature?

 


lat.: natura = essential qualities


Historically, nature conservation was first established and promoted around 1820 by supporters of three major currents:


1. The social-conservative policy
“Mankind and nature create, improve or destroy each other” - Ernst Arndt
Nature is to be protected, because its destruction causes cultural and social decline. Nature as power source for society and regional identity, not only to provide resources, but to strengthen people’s spirit. Landscape unifies political ideals and aesthetic conventions.


2. The romantic ideal
“Idealism versus Materialism” - Ernst Rudolf
Nature conservation held up against industrialism, that follows materialism and economy. An image of nature is created, a picturesque, poetic ideology. Everything connected to industry, such as railways, mines, industrial farming is considered to be damaging that ideal. The interest in nature is purely aesthetically.


3. The natural science policy
Protecting specified areas, such as forests and mountain regions, that are of major value. Criteria are areas with outstanding biodiversity, hosting endangered species or botanical phenomenons.
This movement introduced national parks, conservation areas and nature monuments.


Today, what people connect with the abstract word “nature” and why it should be protected are not very different. People often refer to nature in a romantic way or emphasise the importance of nature for the national or regional identity.


As the publication of the city of Munich show, the Isar re-naturalisation was promoted with a combination of all three currents: The Isar was supposed to be turned back into the river it once
was, strengthening the image of Munich as an alpine, nature-committed city. At the same time, the city wanted to improve water quality and biodiversity, which refers to the third idea.

Sources:

Handbuch Naturschutz und Landschaftspflege, Werner Kobold, 2016, Wiley-VCH Verlag, p.2-8

Sources:

"Baureferat Landeshauptstadt München, 2011" from https://www.muenchen.de/…/baureferat/projekte/isar-plan.html

"ISAR PLAN THE WILD AS THE NEW URBAN?", Frédéric Rossano, Institute of Landscape Architecture, Swiss Federal Institute of Technology / ETH Zürich Zurich, Switzerland

Map of the Isar

 

This topographic map shows the different height levels in Munich. Here, this map is specifically used  to analyse the lower areas around the Isar, which are higher at risk for flooding.


Looking at the already existing shape of the river Isar and combining that with the lower parts of Munich, we created a possible flooding situation. If we look at this possible situation, we can see that Flaucher and Englischer Garten are two of the main big areas which are at a higher risk.

flood area next to the Isar in munich

Competition of Isar Renaturalisation

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An urban river restoration project has been in progress on the River Isar since the beginning of the year 2000. The project was launched in 1995 by the Bavarian Water Management Agency in Munich and the City of Munich under the slogan “New Life for the River Isar”.

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Within the scope of the “Isar Plan” local flood protection should be improved and ecologically valuable habitats for fauna and flora shuld be restored. At the same time, the growing demand of city dwellers for natural landscapes in central urban areas for leisure and recreational use is met in an ideal manner. In all, the joint project of the State of Bavaria and the City of Munich is more than just the restoration of a stretch of the River Isar extending over 8 kilometers in the Munich area (from the southern city border, at the Großhesseloher Bridge, to the inner city at the Deutsche Museum or Museuminsel), it is also an investment in the future. This urban river concept should combine the nature-oriented redesign of a river with an urban lifestyle, and go well beyond simple cost-benefit analyses and is of immeasurable value for the population.

 

The goals are:

  • Protection against the flood

  • Renaturation of the landscape

  • Increase of low water level

  • Regain of ecological functions

  • Improval of  water quality

  • Improval of social qualities

 

The Isar in Munich – An urban river landscape adapts to the winds of change. Ideas on an integrated urban river development concept for the River Isar started in Munich back in the nineteen eighties. Before hydraulic regulation began in the middle of the 19th century, the pre-alpine River Isar flowed in the Munich area in a constantly changing river bed with extensive gravel banks and river branches. The quickly rising floodwater that brought large quantities of debris and gravel from the Alps, regularly changed the river landscape. Areas of Munich situated at lower elevations were regularly flooded. The systematic development of the river bed as well as the utilization of hydropower in the power canal alongside the River Isar in 1920, embedded the Isar in a fixed, linear channel of approx. 50 meters in width with trapezoidal cross-section, comprising the main channel, forelands, flood meadows and flanking flood embankments. As a result of the canal-like development and also through removal of the bedload in the upper course, caused by the Sylvenstein reservoir that went into operation in 1959, the River Isar has slowly but surely lost its natural torrential river character forever. The gradual degradation of the river bed was counteracted by regular placement of low weirs or cross-river sills in the longitudinal course. Reduced flow, unvaried flow conditions and uniform river structures had a detrimental impact on flora and fauna and also on the landscape scenery. Only at the “Flaucher” - which is a part of the Isar floodplains near the inner city that has practically maintained its natural character - can one sense the original flow of the ramified River Isar with its open gravel banks and alternating gravel stone islands. This area therefore also has a model function for the near-natural restoration of the River Isar.

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Tasks for the project:

  • Built-in structures to improve flood protection

  • Expansion of the riverbed

  • Development of the bank areas (shallow shore, upstream gravel banks, renaturation and invisible stabilization of the dikes)

  • Design measures in the river (gravel islands, dissolved bottom ramps, new flat ramps made of block stones)

  • Sterilization of the treated wastewater in the treatment plants with UV light

  • Model was the Isar with wild river character

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A particular challenge is the balanced implementation of the different development goals. No single objective should be enforced at the expense of another.

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Construction period: February 2000 to June 2011

Costs: 35 million euro (of which 55 percent Free State)

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Awards:

1. Award (16.500 €)      

2. Award (10.000 €)      

3. Award (6500 €)

Re-naturalisation as river improve- ment and identity of Bavaria

 

 

Munich Building Department: “The discussion started with the growing fear of flooding in the mid 19th century. The first “corrections” where made to restrict the river and turned it into a settled, linear steam.


This had negative effects on plants, animals and the aesthetics of the river and led to the beginning of the renationalisation project in early 2000. Political committees, federations and the citizens were involved in the public planning process. It is a communal project of the Free State of Bavaria and the city of Munich. The decisions are mainly made by the Free State of Bavaria, represented by the water management office of Munich.


The official main aims are:
1) Better flood control
2) More space and connection to nature for the riverside
3) Better surroundings for leisure and recreation


Excavation: 710.000 m3
Redistribution of gravel: 290.000 m3


The plan is a reaction to the lack of aesthetic quality, public amenities, and elaborated design. The aim is to design the river as constitutive urban element in a near natural state and to regain the character of wild Alpine river”


Baumeister (2003: 10-12): “The project should be aesthetically attractive and enhance the cultural value of the “Isar Space,” combining an open character with prominent urban features.”

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