Change of the Manning´s coefficient in small stream influenced by vegetation

Abstract

Aquatic vegetation in natural streams impedes the flow of water and may increase flood risks. This paper analyses impact of aquatic vegetation density on the dynamics of flow process by evaluation of the Manning´s coefficient value obtained from field measurements. Measurements performed during two years (2020 and 2021) along the part of the Malina stream were used for determination of the Manning´s roughness coefficient value for different extents of river bed overgrowth during the year. This stream, located at the Zahorská Lowland, is a stream with a low longitudinal slope (0.00037–0.00039) and aquatic vegetation occurrence. Value of the Manning´s coefficient is varying during the growing season in the range from 0.025 to 0.157 for the year 2021 and from 0.038 to 0.266 for the year 2021.