Restoring Oxbows in Austria and Germany

Up to the middle of the 19th century, the Danube was a free-flowing wild river in most parts. Maps, pictures and travel reports from that time show a varied river landscape with narrow gorges and wide basins. The Danube consisted, apart from the largest stream, of a water network with various large and small branches and extended riverine woodlands. This natural river system was fairly wide, not too deep, and characterised by unstable banks. Large-scale floods occurred in regular intervals. In correspondence with the water channel, also the location of gravel banks, islands, etc. used to change continuously. In case of floods, several branches merged, islands and banks were reshaped, while new alluvial deposits emerged in other places. The river was in a state of dynamic balance, in which this system could regulate itself. (World Wide Fund for Nature, 2002.)


The forest in late March is a carpet of snowdrops – so many of them that you have to blink twice before you can believe your eyes. The only sounds are the tapping of hundreds of woodpeckers, and the song of other birds. The Danube flows silently, unseen beyond the trees. We walk as quietly as we can, in search of beavers, and almost fall over two young wild boar instead, who crash away through the undergrowth. Nothing disturbs the woodpeckers, who tap on regardless, like a city full of carpenters. Then there is the silver flash of water, and the tell-tale rings in the bark of many trees, made by beavers’ teeth. Sometimes they dig so deep into the tree that it crashes down. Other times they dig just deep enough to let it die by itself. On the far shore of the tributary, tall Canadian poplars stand bare, killed by the beavers’ attentions. The hollow trees provide a perfect sounding board for the Great Spotted Woodpeckers, whose work echoes all the louder now. On the near bank, an ancient black poplar, a native to this region, unlike the hybrid or Canadian poplars – the favourite of industrial forestry – rears up suddenly. We are in Eastern Austria, only 20 kilometres downstream from Vienna, close to the Slovak and Hungarian borders. My guide in the forest is Georg Frank, project manager of the Donau-Auen National Park, based in the small Austrian town of Orth.

“The idea of our national park is to give more space to nature, to initiate dynamic processes…” he explains. So the hybrid poplars, planted in straight lines before this became a park, are only rarely cut down. “The beavers do the job just as efficiently. And slowly the forest gets older, and fills with dead wood, as well as living. And that is good for the insects, and the beetles. Which is good for the birds…”

In 1984, the wetland forests between Hainburg and Vienna were on the brink of destruction. A massive hydroelectric project, planned for Hainburg would have devastated the largest remaining floodplain forest in Austria. Determined opposition by Austrian environmentalists, who chained themselves to the trees, forced the Austrian government to first suspend, then cancel the project altogether – just as Hungarian environmentalists would stop a similar project at Nagymaros on the Danube five years later, while Slovakia pressed ahead with the Gabčíkovo project. In 1996, once it was clear that the Austrian environmentalists’ victory was irreversible, the contract to turn the rare wetland forest into a national park instead was signed in Hainburg. A tall wooden sculpture in front of the church in Stopfenreuth commemorates the bravery of the environmentalists.

Since then, the national park authorities, in close cooperation with the regional and national government, the fishery, flood protection and water management authorities, have re-opened the meandering side-arms of the river which were blocked off in the 19th century. Rocks placed along the shores have been removed in many places, to allow gravel and sand banks to reform. Fish can now breed again in the side-arms of the river, and many species of birds, insects and animals have returned. The National Park has become a model for further wetland restoration projects up and down the Danube.

“There has been a big change in the philosophy of our country”, says Georg Frank. “It was clear after the Second World War that there must be economic growth, and the building of state-of-the art hydroelectric plants was necessary. Then step by step, as the economy and the countryside were developed, people realised that there is more to life than this. That if you want to live in an inspiring country with inspiring nature, you have to protect it. And that is what is happening now.” The bark of the black poplar is furrowed like an old willow, but the branches are gaunt and twisted, black as its name suggests against a white sky.

“This is a very special tree for the Danube flood plains, because rejuvenation of this tree species can only happen in very dynamic habitats, in our case mainly on gravel banks, on islands, and these islands are the result of river dynamics.”

As a result of 16 years restoration work, the river now frequently floods the area between the dyke and the shore, and the park area beyond the dyke is also growing richer with plant and animal species, as forestry and hunting are banned. Finally, we reach the Danube itself, broad-shouldered and fast flowing. A Bulgarian barge battles upstream, the bicycles of the crew chained to its railings, while a Dutch ship glides easily downriver. The Dutch ships have one or two small cars parked in the stern – a mark of the different levels of prosperity of the East, and West European sailors.

On the far bank is the village of Haslau, and just beyond that, the remains of the former Roman city and military camp of Carnuntum, where 50,000 people once lived. Only last year a large complex of buildings was revealed underground – the remnants of a school of gladiators. On the near bank, the same, Uferhaus restaurant has been owned by the same former fisherman’s family for at least fifty years. You can eat pike-perch cooked “in the Serbian style” – grilled, then smothered in garlic – though the fish come from ponds in Hungary, not from the Danube.

For all the work on restoring the quality of the wetland forest, and the river shores, there are still far fewer fish in the Danube than there were as recently as the 1950s, when local children poached fish from the river to sell to the restaurant. There are several reasons. Most serious is the great shortage of the free-flowing stretches which fish need to reproduce. The Gabčíkovo dam, canal and hydroelectric turbines which opened in October 1992 just downstream of Bratislava in Slovakia, prevent fish migrating upstream, just as the first Iron Gates dam between Romania and Serbia blocked the route in 1971. Old prints of the markets in Vienna show the huge sturgeon which once bred in the Szigetköz and Csallóköz stretch of the Danube in Hungary. Orth stands today on what has been reduced to just 45 kilometres of free-flowing river, between the Gabčíkovo and Freudenau power stations. Parks like this are like islands on a heavily regulated river, where the battle continues between an engineering and business lobby who want more dams and a deeper, wider navigation channel, and environmentalists who want to help the river expand, and restore it to some of its former glory. The removal of the rocks piled high along the bank has allowed sand and gravel beaches to come right down to the river, multiplying the places for fish to breed, and creating new recreation areas.

Before leaving the Donau-Auen park, Georg shows me a sturdy wooden pillar with the high water marks of the floods – from 1954, and 2002. The 2002 mark is about 15 centimetres higher than the measurement for the “once in a century flood” of 1954.

“The two marks tell us a shocking story. The volume of water in each case was about the same, but in 2002 the level was significantly higher, and the floods came much faster. This is the direct effect of the embankments, which squeezed the river into too narrow a channel. So we really see the need in our section to work on restoration.” Restoring the river, he says, requires the opposite approach to restoring the forest. The forest just has to be left, to regulate itself, while the river needs pro-active involvement, to undo the interventions of the past, and let the Danube flex its muscles once again. Only then will the floods be seen as a blessing, not a curse.


Hannes Seehofer is standing by a yellow bulldozer when I arrive at Grimsing, in the beautiful Wachau region of Austria, upstream from the town of Krems. A digger is scooping great bucketfuls of earth and gravel out of what looks like a long, wide moat, and workmen are hammering at a wall of iron beams and concrete rising out of the mud, which turns out to be a bridge. This is private land, belonging to the Count of Schönbrühl, whose fairytale castle rises on the far side of the Danube. Environmentalists working in the framework of the Life+ project of the European Union, have won permission to reconnect the Schallemmersdorf side-arm to the main Danube. This is the latest of four projects to restore the Danube riverside in the Wachau. What looks like a giant building site is actually de-construction work – to allow water back into an oxbow from which it has been excluded for more than a hundred years.

The drying-out of the riverside forest which began in the nineteenth century, Hannes explains as we walk through the trees across the island, was made dramatically worse when the hydroelectric dam was built at Melk, just upriver, in the 1970s. At Grimsing, the river level immediately fell two metres.

We reach the Danube, somewhat narrower here than downstream at Orth, but still a substantial river. Just to the West, we can see the fruit of the latest restoration project, a major side-arm, re-opened in April 2006. Within six weeks of it being reconnected to the river, around forty species of fish were found breeding there, of the forty-seven which once lived on this stretch of the Danube, so rapidly can the ecosystem of the river recover if it is given a chance. Species like the pike need the warmer waters which the oxbows provide. Wild carp prefer to breed in flooded forest. All fish are threatened by the wash of passing barges and pleasure craft, which dislodges any eggs they manage to lay on the gravel bank. Each restored oxbow helps replenish the river with fish. While in the Danube delta, ecologists are often in conflict with the fishermen, because of the attempts of the former to prevent overfishing, here they are in harmony with local fishing associations along the bank, who spend tens of thousands of euros each year artificially introducing small fish into the river, for their members to catch. The return of natural reproduction saves them money. Hannes suspects the Danube salmon is there as well, but he has no evidence yet – another of his projects is the improvement of the mouth of the small tributary of the Pielach stream, famous for its salmon,where it enters the Danube. At nearby Rossatz, opposite the famous Durnstein castle where King Richard the Lionheart was imprisoned in 1192, the aptly named Josef Fischer breeds the wild salmon he catches in the rivers, and each year returns thousands to the Danube. “It’s a hobby…” he says, carrying an enormous female fish in his arms, from pond to tub, but after more than thirty years of practice, he is the only successful salmon breeder on the whole river.

Out in the mainstream of the Danube, right in front of the Schönbühel castle, two rocks protrude from the water, leaving a jagged white wake – the Cow and the Calf, as they are known locally, for centuries a serious hazard to ships travelling upstream. The depth here can reach as much as ten metres at high water, and fell to only 1.5 metres in January, in the last period of drought.

“The length of free-running water here is only 35 kilometres”, Hannes says – “it would be more, but the backwaters from the next dam slow the river down…” The shortage of gravel is a problem everywhere in the upper and middle Danube, because the 49 dams in Germany and 9 in Austria stop it flowing downstream. Along those rare stretches where the Danube runs free, it is essentially an Alpine river, and the gravel until recently formed an important part of its natural regeneration. What happens without it is that the storage lakes which form upriver of each dam have developed muddy, sticky beds – similar to the bottom of lakes – which are unsuitable for the reproduction of fish, while downstream the river cuts too deep a channel in the middle of the stream, worsening the sudden impact of floods. One successful innovation in recent years has been the digging of streams beside the dams, to fish to migrate upriver. These cannot be straight, because of the speed of the water funnelling down – the water level on either side of a dam can differ by as much as ten metres – so they are dug in a meandering way, to give the fish more chance. In 2009, according to the Vienna- based International Commission to Protect the Danube River (ICPDR), 22 out of 78 barriers on the whole Danube were classified as passable for fish. The ICPDR has drawn up a list, with the countries concerned, of several more where work should be completed by 2015. These do not, however, include the massive Iron Gates and Gabčíkovo Dams, each over 15 metres high.

Another useful innovation in the Wachau is that the gravel dredged from the main stream to improve navigation, is now returned to the Danube – outside the main shipping lanes. This then forms sheltered islands, on which birds like the little ringed plover can lay their carefully disguised eggs, and behind which fish can spawn, unthreatened by passing ships. A study of the plover and sand martin populations carried out by environmentalists in all ten Danube countries last summer, found “capital cities” of the birds on many sections of the middle and lower Danube, but a major dearth in the much regulated upper sections of the river.

Walking with Hannes along the shore of the island, we finally reach the “mouth” of the side-arm, where the Danube will be allowed to flow back in September this year. A line – three hundred metres long – of rocks will be the last obstacle to be removed, and the water will pour back down into the carefully sculpted channel. More than two hundred thousand cubic metres of material have already been removed to make way for it.

Close to the gravel shore, stands another black poplar – slightly smaller than the one I saw near Orth. A rare red beetle was discovered in its bark two years ago – another sign of the rich diversity of life returning to the restored river.


“The Danube here is really a pity, because it’s not a river anymore, it’s a canal. It has little in common with the Danube as it used to be.” I stand with Siegfried Geissler on a high embankment, overlooking the broad Danube near Neuburg, just upriver of Ingolstadt in Bavaria. His bleak assessment is provoked by the vast storage lake in front of us, upstream of the Bergheim dam and hydroelectric turbines, which form a solid wall across the river, a little to our right.

“So you destroyed the Danube long ago, but now you’re determined to repair it…?” I ask him.

“Exactly!” he sighs, “whereas downstream in Bulgaria and Romania, where it is still pristine, in part, they seem determined to make up for lost time, and destroy it!”

The fruits of his own labours to restore the Danube for the last thirty years may not be visible on the wide-open expanse of the Danube storage lake, but they are spectacular a few hundred metres inland, in the forest. A channel from the Danube flows directly over a meander, on a bridge, into the forest. For the second time on this journey, I have to make sure I am not dreaming. Four kilometres long, the new river pours through sluice gates on the Danube, bringing as much as 600 cubic metres of water a second into the forest, where it spreads out through a network of waterways, most natural or “improved”. Several times a year, so- called “ecological floodings” occur, when the forests are allowed to flood from the swollen river, and even the double stream we stand beside disappears under two metres or more of water. Studies carried out by scientists from the University of Munich have shown a big increase in fish numbers, as a result.

“I hope we have another big, natural flood soon”, says Siegfried. “We need one every ten or fifteen years, because otherwise people forget the power of the river, and start building again, in the floodplain.” In this particular forest, the environmental organisation has bought ten hectares of land for their projects, and leased another hundred and thirty. “The landowners tend to see every tree they cannot cut down as money lost”, he says, “I wish they were more aware of what is being gained.”

How hard was it to persuade local politicians to back the reclamation of the flood-plains? I want to know. Was it because they were more open to the green message, or because of the physical qualities of the forest and the land on which it stands? Both, is the answer.

“We have an area which is still so rich in nature… so it was relatively easy for us to convince our politicians to go with us.” The situation is much harder downstream, he says, between Straubing and Vilshofen, where another group of environmentalists are battling plans to build a new hydro project, on a rare, free- flowing section.

What of the future of energy supply in Germany though? I ask – in the wake of the decision, after the nuclear power station disaster at Fukushima in Japan, to phase out nuclear power in Germany. Does he expect more pressure to build new dams on the last free-flowing sections of the Danube?

“The decision to end nuclear power was an excellent one – we worked for that for decades! But our politicians in Bavaria are also thinking of renewing hydropower again and cutting all the small rivers or the leftovers from the big rivers – and that is a real problem for us.” But existing dams can be improved, to allow gravel, and fish, to pass safely through, or round. More windpower can be tapped, and above all, biomass, from Bavaria’s abundant forests, could be used to create energy. “That would be a better idea”, he continues, than the current practice of selling it to Canada to produce toilet paper. “We don’t need to destroy our rivers. They are like the veins and vessels within our body. For nature, that’s the most important thing.”

Most recent

Newsletter signup

Like it ? Share it !

Share on facebook
Share on twitter
Share on linkedin
Share on pocket
Share on email