Back-Calculation of Manning’s Roughness Coefficient by 2D Flow Simulation and Influence of In-Channel Physical Parameters in a Mountain River, Japan
| Autor: | Hiroshi Takata, Shogo Obata, Tatsuro Sato, Yukihiro Shimatani |
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| Jazyk: | angličtina |
| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Water, Vol 16, Iss 2, p 320 (2024) |
| Druh dokumentu: | article |
| ISSN: | 2073-4441 68724365 |
| DOI: | 10.3390/w16020320 |
| Popis: | This study attempts to back-calculate Manning’s roughness coefficients by repeating a two-dimensional flow simulation to fit the spatially and temporally dense river water-level data observed in Japan’s Yamatsuki River, a typical mountainous river with an average riverbed gradient of 1/50 and an average river width of 17.9 m. Furthermore, we aim to clarify the influence of the in-channel physical parameters on the coefficient of roughness obtained through the above method. In the Yamatsuki River, 16 water-level gauges were installed at intervals of about 40~80 m in the longitudinal direction in the study reach. Manning’s roughness coefficients were back-calculated by repeating two-dimensional flow simulations to match the observed water levels of a flood in 2021 (the estimated maximum flow rate is 11.5 m3/s). The back-calculated roughness coefficients approached a constant value in the range of 0.05 to 0.1 s/m1/3 as the relative water depth increased, indicating that the roughness coefficient can be considered a constant value when performing plane two-dimensional flow calculations for flooding. The roughness coefficient during flooding was found to be correlated with the slope and step height (H)-step length (L)- channel slope (S) ratios (H/L/S). An equation for predicting the roughness coefficient during flooding based on the physical parameters of the channel is also proposed. |
| Databáze: | Directory of Open Access Journals |
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