Regardless of the construction works in the Biała riverbed carried out in accordance with the project, at the end of 2018, as part of maintenance works carried out by PGW Wody Polskie RZGW in Kraków, additional support was provided for the existing rapids on one of its left-hand tributaries – the Binczarówka stream (photo 1).
Rapids were established in 2014 on the occasion of the construction of a new, single-span bridge along the provincial road Grybów – Krynica No. 981 (photo 2). The old bridge was supported by a concrete block, in which a large gap was created during the 2010 flood. At the same time, the escarpment on the left side of the stream was damaged. When building a new bridge, nothing was improved, only the old barrage restored, the embankment was renovated, supplemented with native soil and reinforced with a stone coating. Twenty five honeycomb riffles were built, which was additionally secured with two 0.8-meter-wide concrete straps. The crown of this “rapid” has a straight shape with two overflows. The cascade has chambers about one and a half meters wide and 30-60 cm deep. The chambers are surrounded by stones over 60 cm in diameter. Fish ramp is a barrier impossible to cross by any fish.
The Binczarówka Stream is a fairly important breeding place for several species of fish, including the alpine bullhead, stone loach, common minnow, chub and spirlin (Alburnoides bipunctatus). In a situation of low water levels, they would not be able to overcome the existing device. In addition, below the concrete buttresses, are the beginnings of bottom erosion, which in consequence would threaten the stability of the entire weir securing the road bridge. Therefore, it was decided to modernize it.
Works were carried out aimed at, among others increasing the efficiency of buildings from 2014. The gravel bar has been removed, significantly reducing the light of the bridge (photo 4). The excavated material was used to backfill the gaps in the banks and bottom of the Binczarówka riverbed below the existing weir.
The new construction consists of four transverse stone straps spaced every 5 meters with an additional three oblique inserts, whose task is to increase the number of pools (from three to six). Such treatment significantly reduces the slope between individual chambers (Fig. 1). This structure was designed for the migration of weakly swimming fish species. To stabilize the bottom in flood conditions, the bottom of the pools was filled with boulders with a diameter of about 80 cm.
The task of the new rapid (Fig. 2) is to protect the estuary stretch of the Binczarówka riverbed against further erosion, protect the road bridge and the weir protecting it from damage, and increase the water level in the chambers of the old rapids from 2014. This is to enable fish to spawn upstream, even during periods of low water.
The obtained effect can be considered as an added value, affecting the integrity of the Natura 2000 area (PLH120090 Biała Tarnowska), which appeared to some extent during the renaturalization of the Biała River valley, which is the main goal of the implemented project.
Interestingly, this result was created using the same means and machines that are usually used to regulate rivers …