Floodplain moments – Shifting water levels shape landscapes

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The Rhine floodplains - sometimes flooded, sometimes dried up

Sometimes wet, sometimes dry. You might see the Rhine floodplain here in Rastatt in either state. As a natural floodplain between the land and the river, phases of high and low water levels shift constantly. Like a sponge, intact floodplain areas can absorb impressive amounts of water. That is why alluvial areas like these are our most important natural flood protection. Plus, they clean the incoming water like a natural sewage treatment plant.

The Rastatt floodplains - a nature reserve

Although floodplains only make up 7% of the land surface in Central Europe, over 65% of all flora and fauna communities live here! That is why in Rastatt, 845 hectares of pristine floodplain landscape are strictly protected as a nature reserve.

Kingfisher, beaver and rare plants love the Rhine floodplains

The water dynamics shape the soils and form a mosaic of different habitats, including dense floodplain forests, wet meadows, open waters and reed-covered shore areas. In turn, the floodplain creates space for numerous rare and endangered plant and animal species, such as the kingfisher, the European beaver, the tree frog or the European weatherfish. Pioneer plant species typical of floodplains, such as the water mudwort, also have a place here.

Drawing of a water wave
Drawing of a water wave

Let the water flow - How does the floodplain get flooded? The emergence of floods

Floods and high water are natural events in nature. Animals and plants in flood-prone areas are adapted to them. But how does a flood actually occur?

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It must rain a lot and for a long time

Heavy rains and/or snowmelt are the reason why floods occur.

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The soil can no longer absorb water

Some of the water seeps into the ground. What the soil can no longer absorb soon leads into the rivers via many rivulets.

Drawing of water rising

From small to big

The water from the small tributaries flows abruptly on into larger rivers. The amount of water in the river increases more and more, the water level rises.

Drawing of water rising

The river overflows its banks

The water level in the river rises and rises. If it has no room to spread out, for example because there are dikes and no natural floodplains, or because there is no narrow point or river loop (meander) to slow down the current, the river overflows its banks. A flood occurs.

Drawing from flooded house

Man and flood

We humans have changed the landscape, straightening rivers, destroying floodplain habitats, and replacing landscapes that naturally store water with farmland and settlements. Now floods have a powerful destructive force.

Join in!

Build yourself a mini sewage treatment plant and clean the water like the floodplain.

Plastic cups, pebbles, gravel, sand and coffee filters

For your mini sewage treatment plant, you will need five pudding cups (transparent), a handful of pebbles, a handful of fine gravel, a handful of sand, and a coffee filter. Fill the material into one cup each. One cup remains unfilled. This is where the clean water goes in.

Cup filled with pebbles, gravel, sand and coffee filter

Stack the cups on top of each other as follows. At the bottom is the empty cup, then the cup with coffee filter, then the cup with sand, above it the cup with grit and finally the cup with gravel. Fill soil into a bottle with water and mix everything until it becomes a cloudy liquid. Slowly pour the dirty water onto your mini sewage treatment plant.

Filled cups stacked on top of each other

After some time, clean water collects in the last cup. Compare! This is also how the floodplain works.

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