These past days, dramatic scenes have unfolded all over Germany and Central Europe in general: after unrelenting rainfalls had overburdened the natural absorption capacity of soils and riverbeds, massive floods spread throughout Central European lowlands and threatened the lives and livelihoods of thousands of persons. People had to be evacuated, some even died, and many have to come to terms with the fact that the second ‘flood of the century’ comes a mere 10 years after the 2002 catastrophe and will again swallow all their belongings. Having followed the news quite extensively these past days, I began to wonder – in which way did human activities contribute to or exacerbate the crisis?
To figure this out, one needs to understand the basic workings of floods as explained in the above video. They are mainly caused by unusually high levels of rainfall (which was also the case in this incidence: in the 4 days preceding the floods, around 23 trillion litres of rainfall are supposed to have fallen over Germany) which then causes rivers to overflow and spread above the normal riverbed. Thus far, it is a natural process that has occurred for centuries. Whether the intensity or frequency of such abnormal weather events is affected by climate change is still an ongoing debate; some first studies show evidence that heavy precipitation events in the Northern hemisphere are indeed very likely to have been caused by human-influenced global warming.
What is new and elevates this natural phenomenon to a catastrophe is, of course, the level of human loss and suffering. This is directly linked to the fact that human settlements are often as close as possible to the river – for practical, aesthetic or simply land scarcity reasons – and thereby cover precisely the areas that originally were reserved as floodplains for the case that the rivers swell and surpass their normal riverbed. When construction occurs on these areas, the additional problem of soil sealing is created: the coverage of soil with concrete and other impermeable surfaces reduce the possibilities of rainwater drainage and thus accelerate the runoff flow of water. According to the WWF, the Elbe – one of the rivers with the most dramatic flooding – has lost 80% of its floodplains and forests which originally were able to absorb some of the water pressure.
Another aspect is the problem of soil compaction through the intensification of agriculture: compacted soils have less space to accommodate increased amounts of rainwater; thus, soils are saturated more quickly and water begins to accumulate on top of fields and runs off into streams and rivers. Agricultural land use changes also influence flood risk, since “forests have greater water storage and retention capacities than grassland in general, and grassland has more capacities than arable land“; furthermore, the removal of natural landscape elements in the course of land consolidation also leads to less resistance to flood waves. Thus, a change in cultivation practices – particularly a change away from monocrops that necessitate heavy-duty machinery and also cause soil erosion – can be a pragmatic step towards flood prevention.
The increased human use of rivers for shipping and transport also lead to the channelization of rivers such as the Rhein, making them deeper and straighter in order to facilitate navigation. However, this also contributes to a quicker water flow (since the water flows straight instead of undulating) and a faster pace of the flood wave, resulting in more destruction.
According to this document published by the Environmental Agency of Austria after the 2002 flood, conservation efforts and flood risk management can, and should, go hand in hand. “In many areas, provisions of nature protection and those of passive flood control are in agreement, namely that rivers should be given more space again so as to regain or retain wetlands, which, from the perspective of nature protection, represent valuable habitats for the preservation and restoration of the biological diversity of our landscapes. […] Pure structural engineering solutions are not desirable from the perspective of both the natural balance and the appearance of the landscape. Neither is total technical control of all risk areas feasible economically.” The report’s authors main suggestions were to secure retention areas through deliberate zoning, to re-establish natural river conditions, as well as to adopt river engineering methods closer to nature.
Though the German ministry had originally also emphasized thorough improvements in flood prevention, the WWF criticizes that too little had been done after 2002. If flood prevention measures were put into place, they were mainly localized, too focused on the technical side (e.g. the installation of a single dyke) and thus only shifted the problem further downstream instead of engaging in a holistic solution strategy, according to the WWF’s analysis. According to a 2007 report of the organization, for the Elbe only 1% of the original floodplains were restored despite a general commitment to a more ecologically sound river management strategy.
On the flipside, in recent days German media reports accuse environmentalists of having prevented effective flood prevention projects such as the construction of additional walls and dykes. Right-wing politicians warn that the recent years have seen a “vetocracy” emerge that has endangered the speedy completion of projects, e.g. because the construction of dykes would have necessitated the removal of old trees and endangered the survival of rare species. In this context, a “only-humans-or-nature-can-survive” mentality seems to have emerged, along with a bickering along party lines whether ecological or technological flood prevention is more appropriate. For example, Green politicians remind their accusers in turn that for example of 530 million Euros invested for flood prevention, one Bundesland, Saxony, only used 5 million for the creation of new floodplains – thus only achieving the restoration of 111 out of a planned 7,500 ha in additional retention areas.
Bickering aside, let’s hope that this additional disaster will finally give the impetus for a long-lasting, sustainable reform in land management practices. As the Austrian report points out correctly,
“The management of the areas at risk from floods is simpler, more effective and less expensive than managing the floods themselves.”
Have you been following along the flood developments? Did you know about the potential human causes, particularly the impact of agricultural land use?