Dębica – Wisłoka River

Modernization of existing chamber fish pass with a building

Location:
Wisłoka River – km 56+180
community: Debica,
place: Dębica
Planned term of start:
IVth quarter 2019
Planned term of end:
VIth quarter 2020
Anticipated cost:
1 628 885 Polish zloty

Why do we interfere in a river?

The double weir in Dębica stabilizes the water level at water intake for the needs of an industrial plant. The existing chamber fish pass at weir is ineffective because of some changes which have occurred in the riverbed.

Source:  www.google.com/maps

Modernized structure

The double weir dams water up to the height of 2,2 m and has the width of 100 m. The upper weir and the plates strengthening bottom above the weir were made from concrete. At the right bank 3 concrete pillars are situated. The second weir, situated below, was made from Larsen steel sheet pile cofferdam. The bottom below was strengthened by gabion baskets and a stone overlay.

Because of great difference of levels between the upper and lower water at right bank an almost 40 m fish pass consisting of 6 chambers was built. The fish pass stopped working when, because of erosion below the dams, a weir was made from Larsen steel sheet pile cofferdam. This weir eliminated access to fish pass for fish and other aquatic organisms.

Planned modernization

Within modernization a reconstruction of the existing chamber fish pass is planned. A stone ramp below an existing second weir will be built at the right bank.

A reconstruction of an existing fish pass will include adaptation of 6 chambers, as well as an extension and reduction of bottom of apertures.

In order to make fish migration from all parts of a riverbed below the second weir possible, it is necessary to add two independent inlets in the ramp body which concentrate greater part of water during low-flow flows. The suggested stone ramp will be made on a plan of quadrant with 40 m radius and 1:20 inclination with two migration canals and regularly located bolts in a form of a chessboard. Two such canals in a fish pass were planned: one at the right bank and the other at the part directed to the axis of the river.

Technical drawing of fish pass in Dębica (WTU sp. z o.o.)

In order to dissipate water energy produced by water overflowing over an existing weir and to protect a planned stone ramp from ice floe, baffle blocks were designed in front of it.