Long-lasting heavy rain swelled in the Isar and Loisach district on Monday. This is a very rare phenomenon for February.
Bad Tölz-Wolfratshausen– Long-lasting heavy rain caused swell in the Isar and Loisach district on Monday. In the water management office (WWA) in Weilheim, the situation was closely monitored throughout the day. The forecasts for the flood situation changed again and again - depending on the constantly updated data from the German Weather Service.
In the morning it was still expected that 340 cubic meters per second (cbm / s) would rush through the Isar in the evening in Bad Tölz. Because it got colder during the day and the snow line fell, the all-clear was given later.
Loisach level is expected to peak on Tuesday
In the late afternoon Tobias Lang from WWA still calculated with a peak flow of about 225 cbm / s in Bad Tölz, which should be reached around 10 p.m. He expected a maximum inflow of 180 cbm / s into the Sylvensteinsee. The discharge was increased from 12 to 80 cbm / s from Monday morning to noon and then kept at this level for the rest of the day. "We make a long flat wave out of the fast, high flood peak," explained Lang.
For the Loisach, Karlheinz Daamen from the flood intelligence service predicted that flood detection level 1 would be reached in Schlehdorf and Kochel on Tuesday - further down the river, for example in Beuerberg, then barely. There, the Loisach level rose by a good one meter to about 4.20 meters in the course of Monday until around 4 p.m.
"Very, very unusual," says Lang, is not the dimension of the flood, but the time in the middle of winter. The beginning of February is usually a period of low water. But what remains as snow at this time of year came down as rain since Monday night.
What the municipal utility company did with excavators is now done by nature
In addition, there was hardly any solidified snow at higher altitudes that could have sucked up the rain. Instead, the thin, loose blanket of snow was washed away by the rain and added to the rain masses as a snow melt, as Lang explains. Such constellations have so far been known from low mountain ranges ("Christmas flood") at this time of year.
WWA and Tölzer Stadtwerke had set a low water level when they launched a major campaign for the removal of gravel from the Isar last week. As reported, gravel, which had accumulated in the river bed in Bad Tölz, was to be driven down the river by truck towards Pupplinger Au for flood protection reasons. That, it now appears, does the power of the water on its own.
In consultation with the WWA, the municipal utility company opened the locks of the Isar power plant on Monday morning so that the Isar can flow through freely and sweep the gravel away. This also means that the reservoir has disappeared - and the Isar power station is currently not producing any electricity. This so-called congestion is expected to continue until Wednesday, according to Stadtwerke boss Walter Huber.
Flood danger: Isar promenade and camper parking lot in Bad Tölz closed
"Perhaps we can now completely save the remaining work for the removal," hopes Huber. "The advantage is that the gravel has already been loosened up and should be washed away faster." The removal by truck may have to continue in autumn.
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The town of Bad Tölz was preparing to reach an Isar level of 2 meters in the early afternoon and thus the first flood reporting level. "This means that the Isar promenade and the caravan park on Königsdorfer Strasse could be flooded," said Birte Otterbach, city spokeswoman at 2:30 p.m. Even if the forecasts here also relativized later; The Isar promenade was closed in the area of the Ernst-Thissen-Steg. And the mobile homes were made aware of the risk situation. Newly arriving campers were no longer permitted on Königsdorfer Straße and were asked to drive to the parking lot at the Wee-Arena.
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By the way, according to Lang, the flood control did not affect the fact that construction work is currently underway in the Sylvenstein reservoir. Here, on the east side, i.e. on the Sylvensteinwand, drives and contactor panels are exchanged and renewed.
