Purpose of the investment:

In order to renaturalize a section of the Mleczna River bed, it was designed to perform regulatory structures, which are classified as flood control structures. The aim of the regulation of the Mleczna riverbed section, which enables the restoration of the natural conditions of the riverbed, is to increase the cross-section of the riverbed and to create a right-sided floodplain, which, together with the decreased longitudinal gradient of the river and the increased flow resistance, will delay the flood waters flow to the lower lying areas of the Mleczna river basin.

The assumed tangible material and ecological effects are:

• remeandering (reconstruction of meanders) of the Mleczna riverbed along a 315 m section,
• increase of the retention of the Mleczna river basin by about 5.5 thousand m3 .
• lowering of the water levels in the riverbed during flood flows,
• improvement of water quality,
• slowing down of flood waters outflow,
• restoration of degraded natural and semi-natural hydrogenic habitats,
• restoring the ecological corridor of the river valley,
• improvement of habitat quality for bird species, amphibians, invertebrates, etc.

The scope of the adaptation measure included the following works:

• construction of a new route of the Mleczna river bed along the section of 315 m (meandering) with sectional protection of the bed slopes,
• construction of 4 stagnation bays,
• construction of 10 sequences of deflectors and plosives in the riverbed (sections of faster and slower water flow),
• construction of a large water trough for flood waters,
• reconstruction of the rainwater collector outlet with directing the outlet to the stagnation bay,
• maintenance of the Mleczna riverbed in the section where the riverbed route has not been changed,
• construction of a viewing platform - a wooden footbridge from the Mleczna Boulevards to the riverbed bank.

At the request of WWF Poland, gravel prisms were used in the Mleczna riverbed during the works carried out, which resulted in a very favourable for the environment rise of the water level and increased channel and ground retention. Construction works on the aforementioned task were performed in the period from May 11, 2020 to June 30, 2021, while the design works and obtaining the necessary arrangements, permits and decisions lasted from the beginning of 2018. The Environmental Impact Assessment issued by the Regional Director of Environmental Protection was obtained on August 18, 2019; the decision of the Director of the Regional Water Management Board in Warsaw - water permit was obtained on October 28, 2019; the constraction permit of the Mazovian Voivode to implement the investment in the field of flood control structures was obtained on April 28, 2020.
The contractor of construction and assembly works was the company KAMA BIS Paweł Kaczmarczyk from Warsaw.

The implementation of the project brought the following measurable material and ecological effects:

• re-meandering (reconstruction of meanders) of the Mleczna riverbed along a 315 m section (a 171 m section of new meanders and a 144 m natural riverbed),
• increasing the retention of the Mleczna river basin by approximately 5.5 thousand m3 (3.1 thousand m3 in stagnant bays),
• lowering of water levels in the riverbed during flood flows, thanks to the construction of the Big Water channel,
• improvement of water quality (the evaluation of the results in this respect will be made after the analysis of systematically conducted research on water quality in the river),
• slowing down the flow of flood waters (reducing the longitudinal gradient of the riverbed),

in a longer perspective:

• reconstruction of degraded natural and semi-natural hydrogenic habitats,
  restoring the ecological corridor of the river valley,
  improvement of habitat quality for bird species, amphibians, invertebrates, etc.

Map, project - own source. Photos - own source and Radom Drone

Renaturalised section

Before investment works

Under constraction

After investment