Finally, the long-awaited construction works have started. The action entitled: " Restoration of the bottom of the Łupawa valley; beds of lowland and submontane rivers with communities of chrysanthemums (3260-1), oxbow lakes (3150-2) and ash-alder riparian forests (* 91E0) " is implemented in cooperation with the State Water Holding POLISH WATERS.
Since we have already started construction works, it is worth answering a few questions, and above all reminding what we are planning to achieve, what technical solutions we will use and why we have undertaken the task of renaturation in the indicated section of the Łupawa River.
The investment in question is located to the south of the town of Smołdzino, from the west the investment area is adjacent to the Rowokół mountain. Construction works begin about 210 m upstream from the Smołdzino Hydropower Plant
Before we discuss the goals we will achieve and the technical aspects, it is worth giving this action a historical context. The Łupawa River in the indicated section was changed by man from a naturally meandering river into a canal, for the purposes of the construction of the Hydro Power Plant in Smołdzino, the power plant itself was built in 1912. This gives us over 100 years, during which the river lost its original character, perspective, the implementation of the investment seems even more impressive. To show what the river looked like before the power plant was built, we present a fragment of the map from 1877, where we can see its original course
In simple terms, the entire investment can be divided into two stages, the stage related to flood protection and the stage related to restoration activities. The main objective is to restore the natural character of the river, while maintaining and increasing flood safety.
For this purpose, the line of securing the adjacent areas will be moved from the embankment located by the river to the embankment currently treated as a spare one. In order to adapt the spare embankment to the necessary standards, it is planned to insert a sheet piling in the axis of the embankment, strengthening the body and reducing filtration during the passage of flood waters. Moreover, the strengthening of the embankment will consist in adjusting the ordinate and dimensions of the embankment (crown width, slope inclination) to the regulations required for class IV hydrotechnical structures.
After the flood protection line is completed, it will be possible to proceed to the stage related to restoration activities. Therefore, the main embankment is expected to be unsealed, counting from the fork upstream (to the south), through its complete or partial liquidation, depending on the section of the embankment. Demolition may not be lower than the ordinate of the average water level in the river, thanks to this solution we will restore the polder, currently cut off by the river embankment, to the natural cycle of flooding with flood waters flowing into the riverbed after the flood wave passes. The demolition of the embankment will allow for the simultaneous connection of two right-bank oxbow lakes, which together with the polder were cut off from the natural supply of water from the river.
In the meantime, due to the condition and type of five oxbow lakes on the left bank (from the side of Mount Rowokół), only minor interference with the natural processes taking place in them is expected. The treatments will consist in removing obstacles (logs, branches) from the connections of oxbow lakes with the river, possibly their slight deepening (approx. 20 cm) and lighting by spot removal of selected trees.
In addition, work has been planned to secure two fragments of escarpments subject to erosion, with a total length of about 200 m. The currently progressing erosion on the concave bank poses a threat to the road located at the foot of Mount Rowokół. In order to protect the edges, it is planned to make a full wooden palisade. In addition, a second row of palisade with gutters will be made by the road from the shore side, at the same time a rip-rap stone will be used to protect the whole from erosion.
The solutions presented above show how important it is to find a compromise between flood protection and restoring the original natural state of the Łupawa river valley. We are excited about the potential impacts that will hopefully kick off more restoration efforts on man-made rivers.