The History of the Olza
(Barbara Stalmachova, (from: ”Olza - od pramene po ujście”: „Historia rzeki”, published by: Region Silesia s.r.o. 2000) translated by: D.French
The Olza is not a great river, with a length of only 99 km, in comparison with the world’s longest river, the Nile at 6671 km; the Odra, which the Olza supplies, at 854 km; the Vistula, whose source is close to the Olza’s sources, at 1047 km, the Labe at 1154 km, and the Vltava at 430 km. The Olza has a little of the character of a mountain river and a little of a lowland river over its fairly short course.
We know little about the distant history of the Olza. Maybe only that during the period when the Beskid Mountains were formed as a result of the split of the ranges of the Godula and Istebna strata a 5 km crack appeared – today’s Olza valley – through which the Sarmatian Sea flowed onto this region once again. Then an arm of the sea deposited sandstone on the seafloor; so-called Gródecki sandstone, whose remains can be seen on the slopes of the valley, as the seabed was covered with fluvial gravel. Thus runs the theory of the investigators of the Olza valley, the geologists Ludwig Hohenegger and Uhlig. Successive ice-ages impacted on the region; particularly the third and last when a glacier reached it. Previously, before man appeared of course, animals lived here, including the mastodon, a predecessor of the mammoth, whose half-metre tusk was found in nearby Grodziec. At that time the climate began to cool, in the north masses of water began to freeze and create such an enormous quantity of ice that they began to move towards the south. This lasted tens of thousands of years, before temperatures began to rise again. The third time the cooling was so great that ice covered Europe as far as the Carpathians, and in this region came to a stop at the foreland of the Beskid Mountains. After this period many erratic blocks from Scandinavia were left.
Geologists claim that the Olza was formerly a tributary of the Vistula, and that its waters passed through today’s Pastwiska, Hażlach and Rudnik towards the Vistula. In successive perturbations during the Ice Age and Post-Ice Age the course of the Olza moved westwards and flowed into the Odra.
Many times over the years floods have taken a heavy toll. In our hilly region we experience meltwater floods in the spring and rainfall floods in the summer – and even the autumn. The most dangerous seem to be rainfall floods. We shall describe several such floods about which it was possible to glean at least minimal information from historical records. The information is not complete, but at least it serves to give some idea of what a threat floods were for the people of Cieszyn. From historical records we know about serious flooding in Cieszyn Silesia in the years 1623, 1627 and 1628, after which followed years of droughts. The flood which occurred before 1710, when the Olza shifted its course from near the stronghold in Podobora by about 500 to 700 m to the east to where it flows today, must have been devastating.
The old monastery in Jablunkov was so seriously flooded in 1872 that patients had to be moved to the first floor. On the night of 5 August 1880 Silesia and Moravia were visited by heavy floods. The Olza broke its banks and flooded a wide area around Cieszyn. The floods which occurred in Galicia and Cieszyn Silesia in the second half of June 1894 had serious consequences. The Olza caused severe damage in the Cieszyn region, destroying the flood defences between the “third weir” and the bridge in Baliny flooding and devastating fields. The Ropičanka carved out a new confluence above the old bridge, while in Cieszyn the Olza destroyed the bridge.
On 3 August 1925 after three days of torrential rain the Olza flooded the ground floor of the monastery in Jablunkov, washed two wooden bridges away and destroyed many other things in Jablunkov and elsewhere. The flood which took place in June of the following year had similar devastating effects.
Flash floods around Jablunkov on 12 August 1929 had short lasting but serious results, when the level of the river rose by 3 m, chiefly afflicting part of Jablunkov, Bílá and Lomná.
At the end of September 1931 the Olza flooded part of the spa in Darkov and the recently built railway line linking Český Těąín with Sucha. There was an enormous flood at the end of May 1939, when the level of water in the Olza rose by 4 m in the region of Darkov, and another in the spring of 1940, which saw the Olza flooding a large part of Cieszyn on its left bank.
There were two summer floods in 1949 on the 1st and 19th July when the bridge in Třinec by the offices of the Třinec Steelworks was washed away.
The so-called “Flood of the Century” took place on 18th and 19th July 1970. The Olza rose by 5.5 m. The roller gate dam in the Třinec Steelworks was damaged by the Olza and the section rolling mill by the Neborovka. The Freedom Bridge (Most Wolności) was washed away, and five Polish firemen who were fighting to save it were carried off by the raging waters.
Two years later, on 20th August 1972 the Olza again flooded, rising by 5.5 m again. Flood defences had to be constructed at the Třinec steelworks, as the furnaces, rolling mills, power station were all at risk, while the loss of equipment on the Olza was valued at more than 4.7 million Czech crowns. The floods of August 1985 and particularly the one in July 1997 were dangerous for people living near the lower course of the Olza.
Like other rivers, a large number of people have drowned in the Olza, but this is not the place to discuss this matter in detail.
The Olza had a transport function, particularly in the past. At the end of the nineteenth century timber was still being floated on the Olza for sawmills and the Třinec Steelworks. The remains of special dams on Czarci Potok, above Salajka in Horní Lomná can be seen, from where stockpiles of timber were floated on the Lomná and then the Olza after the spring thaws. Later on at the Třinec Steelworks and in Cieszyn, wing dams would catch the logs and lead them into specially built channels.
There were also plenty of millraces along the Olza; channels of various lengths which channelled water away from the Olza to power mill wheels and then back to the main stream. In the past there were water mills in almost all towns and villages on the Olza, which can be seen in contemporary drawings.