Author(s): Julius Reich; Axel Winterscheid; Thomas Artz; Felix Lorenz; Robert Weiss

Linked Author(s): Julius Reich, Axel Winterscheid

Keywords: Vertical morphodynamics; Bedload transport

Abstract: Flow depth is an important parameter along waterways which - at the lower boundary - depends on the vertical dynamics of the river bed (accumulation and erosion of sediments) as well as on the morphological processes involved. There is short-term dynamics (e.g. migration of bed forms) but also medium- to long-term trends that lead to increasing or decreasing levels (e.g. sedimentation or river incision) of the river bed. To improve planning and design strategies it is relevant to know the minimum flow depth and therefore it is necessary to quantify these morphological processes along the waterway. Vertical morphodynamics can be measured best by means of a systematic analysis of multi-beam echosounding data from which high-resolution digital terrain models are derived. With regard to the considered processes, three parameters have been implemented. The “T90-parameter”, as a measure for the bed form height, is determined by a combination of a wavelet analysis, a zerocrossing procedure and a Monte Carlo Simulation. For quantifying the total vertical morphodynamics the so called “M90-parameter” is introduced. It describes the local fluctuations of the river bed over several time steps around the long term mean bed level. It can be used to identify morphologically active areas. In order to derive long-term trends from the data, a linear regression analysis is applied. The resulting “S50-parameter” indicates erosion and sedimentation areas as well as sections with a stable mean bed level. Based on the obtained parameters, data products can be generated that provide comprehensive insights into the development of the riverbed and the vertical morphodynamics of an evaluated section. From this, both an actual state and concrete recommendations for action with regard to planning and design strategies can be derived. The high degree of automation of the procedure enables the processing of large datasets. The method has already been applied in practice to analyze a several kilometers long section of the river Rhine.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221415

Year: 2022