17 January 2013

Roaming the Croatian Danube-bend

The "Croatian Danube-bend expression in the title may not considered as an existing geographical name. I am not sure if anybody has used this expression before me. In this case it is not the scenery, or the rangy landscape that might resemble us the Hungarian Danube-bend, but it is because of the sudden change in the rivers direction. Let us look at this map, and explore this section of the river between Kopacki Rit and Vukovar (fig. 1.).
1. The Croatian Danube-bend and the mouth of Drava

From the Hungarian Danube-bend to the Drava mouth the Danube flowas almost directly to the south. Since the pleistocene this river bed is characterized by a westbound dislocation. A recent (cca. 10000 years old) depression arount the towns of Baja and Kalocsa has drawn the river in its recent bed. This present day sinking made this section a wide floodplain with many islands and abandoned river branches. It has two famous protected floodplain areas, the Gemenc in Hungary and the Kopački rit in Croatia are functioning as National Parks. As the Danube reaches the Drava river, there is a break in its course, as if the Danube was the Drava's affluent. However this should not fool us, this situation is only a moment in earth history. The present day shape of the Drava mouth is the result of river regulation works beginning in the 19th century (fig. 2.).

2. The mouth of Drava (left from the crane)

The loess hills of the Erdut-ridge diverts the Danube eastwards. This plateau rises 200 feet above the river level. It still bears traces of the Slavonian war between Croatia and Serbia after the Yugoslavian split up: signs of minefields, burned down buildings, roofless houses, slowly recovering catholic churches. Many Serbs, Croatians and Hungarians have fled from the troops, and only a few of them returned, mainly Croatians. We can still find a village with Hungarian inhabitants. Dályahegy, part of Dalj has still a Hungarian majority. Orchards and plough lands characterize this loess plateau. Driving through these lands, it reminded me of the Balaton Uplands in Hungary.

From the plateau we have a clear and far view over the Serbian autonomous territory, the Vojvodina (Vajdaság in Hungarian). Almjaš is our first stop, right downstream the Drava mouth. If we take a look on the map, it is clearly visible that it takes miles for the two water bodies to merge. On the right side, the Drava plume can be traced because of the different sediment substance (fig. 1.).
Due to the merging discharge, the Danube width grows significantly. I had the chance to observe the river regulation works in a short section next to Almjaš (Almás). There are no typical perpendicular rubble dams (so called "spurs"), but T-shaped ones, like in the picture below (fig. 3.). Where these "spurs" connect to the river banks, high water washes under the trees and makes steep slopes.
3. T-shaped "spur" at Almjaš
We can find a huge dam in the Almjaš branch (fig. 4.), in which the built two culverts (fig. 5.) to provide fresh water for the small harbor. The sedimented banks are nowdays collapsing due to the floods, washing away the river banks. When these pictures were taken, the Danube level was not high enough for the boats to leave the harbor (fig. 6.).

4. The small branch of Almjaš

5. Culverts on the Almjaš branch

6. The small harbor

In the 15th century, a fort was constructed in Erdut (Erdőd) utilizing the relief of the loess plateau. Later this relief on the Danube side caused its demise. The underwashed banks collapsed, tearing down the northern walls of the fort (fig. 7.). The Adamovich-Cseh family rebuilt this fort later in the 19th century as a crypt for the noble family. We found one of their tombstones, broken in half with german inscriptions. This family had a manor in the village until 1945, which became headquaters of the Serbian mercenary, Arkan in the Slavonian war.
7. Landslide on the loess plateau threatens the Erdut fort
Parts of the fort wall can be found on the steep slope, covered by dense shrubs. They tried to prevent the landslides with river regulation works, attempting to keep away the Danube from the loess wall. Many perpendicular rubble "spurs" had been buil in the riverbed, relocating the stream channel onto the opposite bank. The spped of the river fell back on the Croatian side, and at the same time sedimentation has started. Due to this sedimentation many new islands emerged from the Danube, under the Erdut castle ruins (fig. 8.). 
The islands of Erdut and an oversight on Vojvodina
The Danube passes around the loess plateau just downstream Erdut like a crescent. At Dalj it turns south again. Next to Vukovar, there is a change in the direction again, this time the Fruska Gora mountains make the river flow east. But this will be another sory.


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