Characteristic of Roughness Coefficient Associated with Discharge in Gravel-Bed River

Kim, Jisung; Kim, Won; Lee, Chan-Joo; Kim, Yong Jeon

doi:10.1007/978-3-540-89465-0_169

Cited by 8 publications

(9 citation statements)

References 4 publications

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“…According to the guidelines tables (Arcement & Schneider, 1989) and the Strickler roughness equation (Kim et al, 2010), and using the measured sediment distribution curve (Figure 2), the Manning roughness was extracted around 0.03. In addition, different values were tested to be sure about the calibration of this important parameter.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

Balouchi,

Rüther,

Schwarzwälder

2024

River Research & Apps

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The river morphology of a braided‐type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. Over the past few decades, scientific attention has been directed toward understanding the coexistence of alternating bars and the consequent emergence of confluences and divergences, all of which interact intricately with the process of bank erosion. It is still rather challenging to estimate or predict the total sediment transport rate in this type of river, especially by considering various hydrologic data and climate effects. This study is focused on the reach of the Devoll River in Albania, located upstream of the Banja dam. Understanding the morphodynamics of this river reach holds significance due to the expanding delta upstream of the dam reservoir. The objectives of the two‐dimensional depth‐averaged approach of the present study are to investigate the temporal variation of braided intensity of Devoll River and the effect of using a discharge hydrograph from hydrologic data compared to the regulated one from the upstream dam on the morphodynamics and sediment transport of the river. After evaluating various parameters such as 11 different sediment transport functions, the best results were reached for a cell size of 5 × 5 m2, Manning roughness coefficient of 0.03, Meyer‐Peter and Müller's sediment function, Hayashi et al. (1980) hiding function, and Van Rijn bed roughness predictor in this study. In addition, the results of comparing satellite images and modeling the river from 2019 to 2023 show that the braided index decreased, and this can be due to the fact that the real scenario of the river has a regulated discharge compared to the non‐regulated discharge from hydrologic data, in the mentioned period.

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Section: Discussion Of Resultsmentioning

confidence: 99%

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

Balouchi,

Rüther,

Schwarzwälder

2024

River Research & Apps

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“…Equation ( 1) is the result of a modification of the Meyer-Peter and Muller equation for the determination of n, based on a detailed analysis of stream data from New Zealand conducted by Witheridge [42]. Equations ( 2) and ( 3), developed by Limerinos [43] and Griffiths [44] respectively, are well established relationships and have been widely used for the estimation of the roughness coefficient [45][46][47].…”

Section: Manning Roughness Coefficientmentioning

confidence: 99%

Discharge Estimation with the Use of Unmanned Aerial Vehicles (UAVs) and Hydraulic Methods in Shallow Rivers

Lagogiannis

Dimitriou

2021

Water

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Although river discharge is essential hydrologic information, it is often absent, especially for small rivers and remote catchment areas. Practical difficulties frequently impede the installation and operation of gauging stations, while satellite-sensed data have proved to be relatively useful only for discharge estimation of large-scale rivers. In this study, we propose a new methodology based on UAV-sensed data and photogrammetry techniques combined with empirical hydraulic equations for discharge estimation. In addition, two different riverbed particle size distributions were incorporated, to study the effect of fine sediment inclusion (or exclusion) in the estimation process. Accordingly, 17 study sites were selected and six different approaches were applied in each. Results show that at 75% of sites at least one approach produced an accurate discharge estimation, while in 10 out the 17 sites (58.8%) all six approaches produced accurate estimations. A strong correlation between a threshold value for the hydraulic radius (Rh = 0.3 m) of cross-sections and high estimation errors for sites exceeding it was also observed. The fine sediment inclusion improved only the performance of certain approaches and did not have a consistently positive effect. Overall, the relatively high percentage of sites with satisfactory discharge estimates indicates that using UAV-derived data and simple hydraulic equations can be used for this purpose, with an acceptable level of accuracy.

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“…So, it is important to calibrate the model before using it for floodplain mapping. Roughness coefficient being a critical parameter in the gravel bed river [23], the reliability of its value defined the accuracy of the prepared floodplain maps for the rivers in Nepal. Therefore, we calibrated the HEC-RAS model before using it for simulation to prepare floodplain map based on the parameter -Manning's roughness coefficient.…”

Section: Introductionmentioning

confidence: 99%

Floodplain mapping of an ungauged river: A case study on Seti River in Pokhara, Nepal

Basnet,

Acharya,

Bhandari

et al. 2024

Himalayan J. Appl. Sci. Engin.

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Settlements and infrastructures along the banks of Seti River in Pokhara, Nepal are at high risk of flood. Floodplain mapping for ungauged Seti River is not straightforward like the one for gauged rivers. Main goal of this study was to prepare floodplain maps along the ungauged Seti River in Pokhara, as a case study, using one-dimensional HEC-RAS model. First, catchment area ratio (CAR) method was applied to find annual flow in ungauged Seti River based on flow data of gauged Mardi station. Once the annual maximum flow was estimated for sufficient time length (i.e., 42 years), peak flood was predicted using Gumbel method for various reaches of Seti River within Pokhara. Thus, estimated peak floods were also compared with the peak floods predicted using Gumbel method based on the annual flow data of Tanahu station. As the specific discharge observed to be comparable with each other (difference ≤ 2.68%), CAR method found be a reliable one that is useful for ungauged river. Then, Cowan’s approach was applied to estimate Manning’s roughness coefficient (n) and used it for calibration of HEC-RAS model. Cowan approach found to be a best alternative for ungauged river as the comparison of modelled flow depth with measured flow depth yielded only 3.82% difference. Finally, 1D hydraulic modelling was performed using calibrated HEC-RAS model with available 12.5 m resolution DEM terrain data. Floodplain maps were prepared based on the HEC-RAS simulation results coupled with Google Earth map. The flood inundation area within Pokhara was found to be 2.76, 3.05, and 3.59 Km2 for the peak flood of 20, 50, and 100 years return periods, respectively. Moreover, Laltin Bazar and Gaighat areas were identified to be at high risk of flood such that these areas found to be inundated with 20 or greater years return period floods, compared to Ramghat area which was observed to be flooded with the peak flood of 50 or more years return period. Floodplain maps of this study could be used for preparing flood hazard maps, planning infrastructures, and flood management.

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Characteristic of Roughness Coefficient Associated with Discharge in Gravel-Bed River

Cited by 8 publications

References 4 publications

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

Discharge Estimation with the Use of Unmanned Aerial Vehicles (UAVs) and Hydraulic Methods in Shallow Rivers

Floodplain mapping of an ungauged river: A case study on Seti River in Pokhara, Nepal

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