The Salzbach originates from the Rambach and Schwarzbach canals. The Wellritzbach and Kesselbach also flow into it under Luisenstraße. Its listed stream channel runs under Wilhelmstraße, Friedrich-Ebert-Allee, Bahnhofsplatz and the railroad area to the main sewage treatment plant. From the Theodor-Heuss-Ring, the Salzbach is openly visible again and runs across the "InfraServ" plant site, over the main sewage treatment plant site, parallel to the Hammermühle and through the "Mühltal" allotment garden site. The entire open drainage cross-section is in great need of rehabilitation.

In the affected planning area, which is around two kilometers long, the Salzbach is designed as a double trapezoidal channel with banks of different widths. A trapezoidal channel means that the river bed and the edges of the watercourse form a trapezoid.

Due to the large volumes of water to be diverted during heavy rainfall, the design of a continuous near-natural channel poses a challenge.

There are no spawning and recreation zones for aquatic organisms and few near-natural structures in the heavily engineered stream bed. Only the deterioration of the walled drainage channel has somewhat "upgraded" the structure for living organisms and is already being accepted by fish. Restoration of the section is necessary as the stream bed is collapsing.

The Salzbach has been heavily modified by man. The stream has been straightened and the bed and banks have been set in concrete to allow large volumes of water to be drained away quickly.

There are only gaps in the traditional wooded fringe or riparian strip that would ideally shade the watercourse. Due to the smooth bed and the lack of structural elements such as stones and deadwood, the water flows very quickly and is therefore difficult for small fish and other aquatic organisms to pass through.

The bed of the watercourse is severely damaged and is further damaged with every strong outflow.

There are several crossings and bridge structures in the entire area. The low heights of some of the structures represent bottlenecks for flood runoff. For this reason, the planning office developed a 2D hydraulic model to show the effects of renaturation on flood runoff. This is because the renaturation should take place without worsening the flood runoff.

The listed bridge structures will not be affected by the planning and will retain their function. The riverbed under the bridges is often very slippery and prevents fish and organisms living in the riverbed from migrating. Migration is to be made possible again by renaturalizing the riverbed.

As flood protection plays a central role in the area of action, a compromise must be found between a near-natural design and ensuring the discharge capacity. The more natural the bed, the rougher it is due to stones and gravel. This reduces the drainage capacity of floods. To counteract this, the cross-section through which the water flows must be enlarged.

Prior to the structural implementation of the measure, a water law permit was issued, taking nature and soil protection into account.

The measure is being planned by the engineering firm "INROS LACKNER SE" from Wörth am Rhein, which won the EU-wide tender for the planning process.

As the project is a measure from the Hessian program of measures under the EU Water Framework Directive, it is being funded. The funding rate is made up of the EU Water Framework Directive program and the funding for flood protection measures.

The total cost of the measure is currently estimated at 6.8 million euros. If the measure is not implemented by the end of 2027, there is a risk of fines being imposed by the EU. The costs for the necessary restoration without renaturation have also been calculated and amount to 2.3 million euros. As these are not eligible for funding, they will be deducted from the total eligible amount for renaturation.

Aquatic organisms in particular benefit from the measure. The landscape will also be enhanced by the renaturation in this area. The course of the stream will green itself through natural planting, which will benefit microorganisms.