Cyclic rejuvenation

Nature and safety combined

Safety measures and extraction of clay, sand and gravel go hand in hand with nature development along the big rivers. Mineral extraction creates room for water but also offers new prospects for nature in the river forelands that vanished long ago. However, some places in our river area have dikes so close to the river that restoration of natural elements like wooded banks and alluvial forests may form an obstacle for the water. Cyclic rejuvenation may preserve the room for water and also take advantage of the natural dynamics of large rivers.

Expelling primal powers

In former times there were plenty of riparian forests, river dunes and side channels along the rivers. The river forelands held an unprecedented rich ecosystem. During floods, the power of water or floating ice levelled obstacles like forests and wooded banks. The river forced flooding and it continuously altered its course. By doing so, it always kept enough room for draining the water and rejuvenated nature every now and then. This process was brought to an end by men's intervention. People wanted to cultivate the lands along the river, and live there, and kept it in a straightjacket of groynes, dikes and quays. The unruly river powers had been tamed.

From primal power to mechanical power

Since 1990 we have seen a reverse development. The river is once more allowed to show some of her old powers in the new nature areas along the Waal, the Rhine and the Meuse, and flora and fauna are recovering. Riverbanks are gay with rare riparian growth, shifting sands are re-established and lush alluvial forests change the forelands into a real live jungle.

Nevertheless, in some places the success of nature development may conflict with the room that water sometimes need. A fast-growing alluvial forest can have a restraining effect and give upward pressure causing a rise in water levels of some centimetres. Sand and gravel sediments can also reduce the room for water. Considering the fact that men curbed the primal powers of the river, men must also keep the inundation area 'clean'. We intervene in a way that fits in with what the river would have done. This method is what we call cyclic rejuvenation.

Making a virtue of necessity

The measures taken for cyclic rejuvenation are adapted both to the local qualities of the river, and to the rhythmicality of nature. Clearing and digging activities must therefore take place in the flooding season, between September and March. The wood goes to the bio power plant for generating green energy and sand and clay will be marketed as well. You may also see heavy equipment on the terrain, but this is unavoidable if the job must be done in a limited time. It may take some getting used to again for the nature lover and the holidaymaker: the work itself and the deep marks it leaves behind can be far-reaching, but then the former processes of erosion of the forest and flooding of the river did not take a soft line either. Expectations are that the marks will quickly be erased after high water and a growing season, and the imitated destruction of brute forces will eventually contribute to ecological restoration: creating ever-changing pioneer conditions where myriads of plants and animals will find a suitable place.

         Natural Process Cyclic rejuvenation
  Erosion of alluvial forest Digging side channels in a closed forest
  Erosion of side channels Digging out a silted-up trench
  Breaking through riverbanks Perforating sand walls or removing transverse dams

Pioneering

Cyclic rejuvenation creates numerous opportunities for pioneer species: from sandy shorelines to gravel banks and from silt-rich shores to meter-high steep walls. Wet soil alternates with dry land, and nutrient-rich soil with poor ground, to accommodate numerous specialised plants and animals. Many small insects feel at home on the sandbanks, and are being hunted by sand and gravel wolf spiders, which in turn are prey for bird species like small plover and common sandpiper. Trees like osier and black poplar are even fully dependent on these wet, open places to sprout. And plenty of them will take root on a bare sandbar.

The role of large herbivores

Old clay pits form a special obstacle for the water flow. These pits date back to the time that nature management did not use large grazers, and wild growth was left to its own devices! Natural grazing with cattle and horses cannot stop the development of woodlands, but can curb it. The grazers make short work of sprouting trees and shrubs. An addition in the form of woodland grazers like red deer will take care that trees and bushes will get even less chance to grow. Studies have been started into the effect of letting red deer return to river forelands. Another high-calibre tree browser is the beaver. Here, in the Gelderse Poort, their impact has been impressive! They cut down many trees close by the waterways and create an open space. The expected growth of the beaver population will make their influence felt even more.

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