Abstract
This paper deals with results of a systemized overview of the Chézy roughness coefficient calculation problem as one most frequently used empirical characteristics of hydraulic resistance. The overview is given in the context of the formation of reliable empirical data needed to support hydro-engineering calculations and mathematical modelling of open flows in river channels. The problem topicality is because of a large number of practical tasks which need such a pre-research. In many cases, the accuracy of determining empirical hydraulic resistance characteristics can largely affect the accuracy of solving tasks relating to designing hydraulic structures and water management regardless of chosen mathematical models and methods.Rivers are characterized by a significant variety of flow conditions; hydraulic resistance to flows in rivers can thus vary widely determining their flow capacity. Considering the variety of river hydro-morphology and hydrology, the Chézy roughness coefficient often appears to be the most complete characteristic of hydraulic resistance to open flows in river channels comparing with other integral empirical characteristics of hydraulic resistance.At present, there are a large number of empirical and semi-empirical formulas to calculate the Chézy roughness coefficient. The main aim of this study was to analyze and systematize them in the context of providing proper support to the open channel hydraulics tasks. To achieve the aim of the study, a literature review regarding the problem of determining the integral hydraulic resistance characteristics to open flow in river channels was performed, as well as formulas used to calculate the Chézy roughness coefficient in practice were explored and systemized. In total, 43 formulas to calculate the Chézy roughness coefficient, as well as 13 formulas that can be used to estimate the Manning roughness coefficient were analyzed and systematized. Based on all these formulas, about 250 empirical equations can be compiled to calculate the Chézy coefficient depending on hydro-morphological peculiarities of rivers and river channels, hydraulic conditions, formulas application limits, and so on.
Highlights
Rivers, riverine valleys, and riparian territories have traditionally been considered by humans as an important resource environment, despite essential threats connected with natural river waters [1]
The second group consists of formulas in which the value of hydraulic resistance is determined by the height of protrusions of the roughness of a channel or average diameter d of soil particles making up the bottom and banks of a river channel, or the height hr and length lr of the river bottom ridges:
The accuracy of determining the hydraulic resistance characteristics can largely affect the accuracy of solving tasks relating to designing hydraulic structures and water management of rivers regardless of chosen mathematical models or methods
Summary
Riverine valleys, and riparian territories have traditionally been considered by humans as an important resource environment, despite essential threats connected with natural river waters [1]. Rivers are still the main source of drinking, industrial and agrarian water supply in the world, serve as reliable transport routes [2], and provide hydropower development [3]. They are extremely attractive places for urbanization and mass settlement of people. Rivers are among the crucial natural ecosystems, both local ones and of the world [4], and are important for the recreation and tourism industry [5, 6]. More than one billion people in the world live in areas adjacent to rivers [7]
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