The Hachinger Bach is usually a harmless body of water. Between Oberhaching and Munich-Perlach, it splashes along at most knee-deep at a leisurely pace, and especially in hot summers like these, you can be lucky if you can still reach the water with your feet for additional cooling while eating ice cream on the small bridges in Unterhaching.
But the brook can also do something completely different. A low-pressure area lasting several days or a short period of heavy rain can quickly swell the cozy water vein of the Hachinger Tal to a menacing size. And then what? After many years of waiting, efforts are apparently being made to come up with a joint flood protection concept.
The neighboring communities have long been affirming their interest in a coordinated plan, because up to now it has been agreed that risk management cannot be achieved on its own, but only through intermunicipal cooperation. Various reports have been commissioned since the early 2000s and calculations have been made for the so-called hundred-year flood.
After the Pentecost flood in 2013, everyone reaffirmed their desire to pull together to prevent properties and roads near the creek from flooding again. But before a concept can be implemented, everyone has been waiting for years for a groundwater study by the city of Munich, which was announced in 2015 and commissioned in 2018. Nothing has happened since then. The water management office in Munich has now asked the neighboring communities for a meeting in mid-September.
In the years 2011 (photo) and 2013 there was flooding at the Hachinger Bach.
(Photo: Unterhaching Volunteer Fire Department)
One of the reasons for this invitation, which arrived shortly before the summer holidays, was apparently our own flood protection plans in Neubiberg. Because Mayor Thomas Pardeller (CSU) takes far too long there. “We’ve been talking about it since 2014, but so far nothing of substance has happened,” he recently complained and announced that he might also create retention areas on his own. In Unterhaching, the neighbors were surprised to learn about these plans, but remain calm. “Flood protection is important, but we’re still waiting for the results of the study,” says City Hall spokesman Simon Hötzl.
There is even a water playground in the landscape park.
(Photo: Claus Schunk)
This expertise is considered so important in Unterhaching because they know there that, for example, in the area of the water tower, where the cellars keep filling up, the groundwater pressing from below is a particular problem. It is known that the level of groundwater along the course of the stream between Deisenhofen, where the Hachinger Bach springs from the former glacial drainage channel, and the Berg am Laim seepage point fluctuates considerably. Which complicates the calculations.
Hötzl emphasizes that municipal planning sovereignty is an important principle and that every municipality can therefore take action. At the same time, people in Unterhaching are a bit surprised about the advance of the Neubibergers, because “ultimately the residents on the lower reaches benefit from measures on the upper reaches,” the Unterhaching town hall is convinced.
However, a motion by the Greens parliamentary group from September 2021, which calls for the adaptation and implementation of an inter-municipal flood protection concept, shows that people in this municipality are also slowly becoming nervous because nothing is progressing. Reason: “Due to the rapid climatic weather changes, there is an increasing risk of rain for the district and municipalities. The risk of extreme heavy rain events is growing.” This June, the Greens once again called for “urgent treatment”.
In part, the creek is forced into a tight corset, as in Unterhaching between Hauptstrasse and Burgomaster-Prenn-Strasse.
(Photo: Angelika Bardehle)
Last year in Oberhaching, too, people were startled by the storm disaster on the Ahr and Erft, when heavy rainfall in July caused the rivers to swell to torrents and washed away everything that was in the way with tremendous force. A few days later, the bobsleigh and toboggan run at Königsee was destroyed by a storm with precipitation of around 100 millimeters per square meter within 24 hours.
In June 2021, Oberhaching also experienced a very local hailstorm with precipitation of 25 millimeters per square meter within 25 minutes. In January, the environmental committee therefore decided to recalculate the flood situation at Hachinger Bach with regard to heavy rain events. The data is now available and will be presented at the meeting after the holidays. According to Martin Weidenhiller, head of the environmental office in the town hall, the new calculations have shown that even in the event of heavy rainfall in the community, only the 15 main and 15 outbuildings that are already known to be at risk would be affected by flooding.
Weidenhiller does not expect fundamentally new findings for Oberhaching from the groundwater study of the state capital. According to the Department for Climate and Environmental Protection, this should be presented to the Munich City Council at the end of the year or early next year. They do not want to comment on this in advance. A spokeswoman said that the department for climate and environmental protection was not aware of the plans of the municipality of Neubiberg.
The water management office in Munich, on the other hand, an authority of the Free State of Bavaria, is aware of Neubiberg’s initiative and therefore sees it as urgent to bring all the neighboring communities together again. Marian Gaertner, department head for the district of Munich, says: “The meeting will be about re-determining the flood area and confirming that we can find the best solution together.”