ASSESSMENT OF THE INFLUENCE OF LARGE ROUGHNESS ELEMENTS ON HYDRAULIC CONDITIONS OF WATER FLOW IN THE BĘDKÓWKA STREAM CHANNEL

Aim of the study The paper presents the results of studies carried out in the channel of the Będkówka stream that were to assess the influence of large roughness elements on the change of value of roughness and resistance coefficients. Material and methods In a stream section selected for the study nine measurement cross-sections were designated and in three of them large roughness elements were present. Dimensionless resistance coefficient (λ) was calculated from the Colebrook–White equation. Results and conclusions It was stated that in the cross-sections, where large roughness elements were present, the values of water flow velocity, resistance coefficients, as well as roughness coefficients are higher than in other cross-sections. Also, the sectional cover coefficient (ω) and the degree of change of roughness coefficient Δn were calculated. Regressive dependency Δn = f(ω) of assessment of the hydraulic conditions of water flow change, which is expressed with the change of roughness coefficient was defined.