Two workers, dressed in traditional work clothes, are pulling wood out of the Alluvial Canal.
Two workers, dressed in traditional work clothes, are pulling wood out of the Alluvial Canal.

The Bohemian Forest's / Sumava's “Gentle Eighth Wonder of the World”

Spanning 14,000 hectares, removing timber from the remote regions of the primordial forests of the Bohemian Forest massif was mostly handled with horse and cart in the 18th century. As a result of the increase in timber demand due to rapidly growing urban centres, the forest industry’s importance started to rise.


Zahlreiche Holzschwemmer bei der Arbeit. Schwarzweißfoto.

The Schwarzenberg Alluvial Canal

In 1774 young forest engineer Josef Rosenauer presented to his employer, Count Schwarzenberg, an idea that was declared insane at the time. Today, it is regarded a stroke of genius. He planned to build a waterway with a 0.2 percent gradient to float logs from the northern hills of the Bohemian Forest all the way to the Große Mühl River via the European watershed using an intricate system connecting creeks, culverts and locks. From there, it would be possible to float it to Vienna via the Danube. Firewood had become scarce in the rapidly growing capital, resulting in exceedingly high prices.

His contemporaries laughed Rosenauer's “absurd” vision off as, so they thought, creeks don’t flow uphill, and at first, the Count rejected his idea. He was so convinced of his idea, however, that, in 1778, he even offered to cover the first year’s construction costs himself. His adversaries quickly stopped laughing at him when Rosenauer managed to outwit nature with his advanced canal system.

Together with more than 1000 workers, “Schwemmdirektor” (‘Canal Director’) Joseph Rosenauer built the “Old Canal” (39.5 km) from Hirschbergen to the Große Mühl River between 1789 and 1793, the canal passing the European watershed between the Elbe and Danube Rivers at Rosenhügel.
At Haslach, this canal floats into the Große Mühl River, on whose waters the logs were floated all the way to Neuhaus an der Donau. There, they were loaded onto boats and rafts that took eight days to reach the imperial capital and residence city of Vienna.

After Rosenauer's death, the “New Canal” was built from 1821 to 1823 by Ernst Mayer (the new ‘Canal Director’) and connected Lichtwasser with Hirschbergen (12 km). A 419-m tunnel was dug so that the designers didn't have to build the canal around the timber forest at Hirschbergen, which would have required a 19-km section. Now, the Canal's entire length was 51.5 km.

Most of the time, logs were floated down the Canal around the clock. Some 700 employees were responsible for monitoring, guarding, pulling the wood onto the shore as well as stacking and loading the logs onto boats and rafts. In total, approx. 8 million cubic metres of firewood were floated down the Canal in the course of a century – to be used in the imperial and residence city of Vienna. The engineering marvels along its route include the “Hirschberg Tunnel” and the “Morau Escarpment”.
The so-called “Viennese Canal” was closed in 1890. After 1893, it was faster and cheaper to haul the timber on the cars of the new Mühlkreis Railway. The last logs were floated from Rosenhügel to Haslach in Bohemia in 1930. Since 1963, the Bohemian sections of the Alluvial Canal have been listed historical monuments. Today, the Canal is often called an engineering marvel and was celebrated as the “Gentle Eighth Wonder of the World” after the fall of the Iron Curtain in 1990.

Canal Director Joseph Rosenauer (* 1735 - 1804) in Cesky Krumlov

Technical data:

Old Canal (built between 1789 and 1793)                                                          39.5 km

  • Hefenkriegbach – Rosenhügel (1789)                                                      32.0 km
  • Hirschbergen – Rosenhügel – Zwettelbach – Gr. Mühl (1791-1793)      7.5 km
  • Construction of 87 bridges, 157 culverts, 22 locks and 20 rock weirs

New Canal (built between 1821 and 1823)

  • Lichtwasser – Hirschbergen                                                                                    12.0 km
  • Construction of the Hirschberg Tunnel                                                                  419 m

Canal length

  • Lichtwasser – Gr. Mühl  51.5 km
  • Lichtwasser – Danube  80.0 km

Data on floating operation

  • Float speed                                                            3.6 km/h
  • Float time from Lichtwasser – Hirschbergen       3 hours
  • Average gradient                                                     0.2 %
  • Water supply                                                            27 feeder streams, 3 retention basins, water reservoirs Plöckensteinersee Lake
  • Minimum water level for floating                          0.40 m
  • Optimum water level                                              0.80 m
  • Floating period                                                        April to June
  • Quantity of logs:

Annual minimum                                                                40,000 m3 (1791)
Annual maximum                                                               130,000 m3 (1849)
Total                                                                                     approx. 8 m. m3 (1791 – 1890)