Summary:

The paper presents current technical state of the weir and its impact on the conditions of high water flow. Fixed weir at 37+300 km on the River Uszwica situated at Brzesko town has been the investigated object. The spillway of the weir was modeled according to Creager curve. A water intake for the nearby Okocim Brewery owned by Carlsberg company is situated within the influence of the weir damming section. The existing weir was constructed in 1913 by count Goetz. The technical state of the construction was assessed on the basis of an inventory conducted in 2005. It revealed that concrete elements of the structure are in good technical condition, despite some damage on the lower site composed of “stepping stone” and concrete slab of the outlet. Damage formed on the joints of these two elements and on the side walls of the weir does not affect water flow conditions. A scour hole has formed below the slab of the outlet which gradually uncovers the slab founded on coarse sands and gravel susceptible to washing out. Determined was also the weir capacity by computing the flow discharge for bankfull discharge of the weir equal to its side walls on the upper site. It was demonstrated that too low spillway capacity does not guarantee effective water flow in the weir gauge. The effective discharge established for the third class hydrotechnical structures is Q_2%=291.34 m³·s^-1. This discharge also overflows the river bed above the analyzed object causing flooding of the adjoining areas.