Käsbach
The Käsbach flows through Kostheim and flows into the Main. Within the village, the stream is very narrow and is located in a reinforced concrete channel. This prevents the stream from developing independently. In this area of the Käsbach, at Siebenmorgenweg, flood situations occur more frequently.
What has already happened - the first renaturation section
In 2017, the Käsbach stream above Siebenmorgenweg up to the street "Am Blauen Garten" was renaturalized. There was an acute need for action here, as the water wall was threatening to collapse.
In order to continue the renaturation of the watercourse within the village, the area below Siebenmorgenweg was to be rebuilt in a similar style.
Second renaturation phase in winter 2023
The renaturation of the Käsbach was carried out in the area between "Siebenmorgenweg" and the railroad tracks at "Dornfelderweg". The watercourse in this area was assessed as "heavily modified" to "very heavily modified". The state capital of Wiesbaden therefore also had to take action here.
What did it look like before the renaturation?
Who benefits from the measure?
Aquatic organisms in particular benefit from the measure. Due to the subsequent good passability, distant biotopes are reconnected with each other. Even during the construction phase, microorganisms were observed colonizing the new river bed. The renaturation will also enhance the landscape in this area of the Käsbach.
How was the second renaturation phase carried out?
Due to the obstruction, the Käsbach had a water width of around 2.15 meters at the level of the renaturation section. The plan was to use the entire 3.30 meter wide section of the watercourse and widen it as much as possible. In flood situations, more water can be collected in this section of the watercourse, which can alleviate flooding.
The river bed, which was previously around one meter wide, was widened to 1.40 meters. However, a meandering low-water channel was created in order to ensure a minimum water level in the streambed for trout, a key fish species, even in dry periods. At higher discharges, the entire watercourse bed is flooded. In addition, basin-like depressions, so-called pools, are created. These serve as a water-filled refuge for aquatic organisms at very low water levels.
The bank area is built up with the help of stones set up like steps. The river bed has been reinforced with a stone insert. This is intended to prevent parts of the bed from being washed out during heavy runoff. To improve flow diversity, individual stones were placed irregularly in the bed of the watercourse. Flow diversity means that the water flow can vary in strength in different areas.