“City, country, river – The changing face of a river” dialogue forum hosted by the Munich Re Foundation on 21 June 2005

The Isar Plan – A win-win(-win) story

River restoration creates winners: flora and fauna, the residents of Munich and the city itself all profit from the return of the Isar in the southern part of the Bavarian capital to its natural state. This was demonstrated by Dr. Klaus Arzet in the second water dialogue forum hosted by the Munich Re Foundation in Munich.

“I want to focus your attention on an important current topic.” These were the words of introduction of Dr. Klaus Arzet, Head of the Wasserwirtschaftsamt (Water Management Bureau) in Munich to his presentation on “The changing face of a river – Restoration of the Isar”. An audience of some 130 listened attentively to the “walk through time and space”, from 1800 to the present.

History

The Isar, an alpine river that is 260 km long, has its source in the Karwendel Mountains and flows into the Danube at Passau. The river runs through the Bavarian capital Munich and is a traditionally popular recreational destination. At the beginning of the 19th century, the Isar, which had regularly caused flooding in the Au, Tal and Lehel quarters of the city, was tamed and channelled – in many sections into straight canals built of stone and concrete. Much later – at the end of the 1950s – the Sylvenstein Reservoir in the Karwendel Mountains, with a capacity of 80m cubic metres, was built to regulate the water of the Isar, even when at its highest levels.

At the beginning of the 1990s, the Bavarian State and the city of Munich decided on a major restructuring plan for the river. The aim of the Isar Plan was to optimise flood control and improve urban recreational quality by providing “more space and greater proximity to nature in the river environment” Dr. Arzet explained. “In the heart of the city, the river channel is too narrow to permit any redesigning. The canal structures cannot be broken up. This is true of many cities, as it is for the Isar downriver from the Praterinsel as well.”

A river takes on a new look

The first construction measures were undertaken south of the city, at the Marienklause, in 2000. Two of the three sections have now been completed. The river has taken on a completely new look. Hidden behind the natural haven, the gravel banks, meanders and islets, there are complex protective structures, invisible dyke reinforcements, sophisticated tree protection devices and fish ladders. Dr. Arzet was pleased to report that, when not disturbed by recreation-seekers and swimmers, the fish are accepting these ecological bridges. Flora and fauna are developing splendidly and initial surveys have shown that, in just a short period of time, biodiversity has greatly increased.

One important reason for restructuring was to optimise flood control. In May 1999, severe flooding in southern Germany that caused property damage in Bavaria amounting to several hundred millions of DM highlighted the importance of flood control in Munich – in spite of the existence of the Sylvenstein Reservoir. Only because the capacity of the reservoir had been increased not long before did Munich escape flooding.

The controversial last section of construction down to the Museumsinsel is to be undertaken this year. Residents and riparians were initially not able to agree on a plan. “ We will create alpine river structures here as well, whilst preserving the historic Cornelius Weir at the Deutsches Museum. Summing up, Dr. Arzet stated that the Isar plan was due to be completed by 2008.

All is well that ends well

The attractiveness of the Isar as a river of recreation has been greatly enhanced. The ambitious project is also attracting the interest of specialists and delegations from abroad. The Isar, an example for other rivers? The flood control measures are a considerable achievement. They meet guidelines that apply to all of Bavaria and provide for implementation of high-level flood control measures throughout the federal state by 2020. “Last but not least”, Dr. Arzet reported with a note of pride that “we have restored some of nature’s original appearance.” The total costs, which amount to some €30m for the overall scheme, are low when compared with other expenses of the city of Munich and the Bavarian State. In the final analysis, the Isar plan is a win-win(-win-win) project. The people, the ecology, the city, the Bavarian State and the Isar itself all stand to gain.