Flow Resistance in Lowland Rivers Impacted by Distributed Aquatic Vegetation

Okhravi, Saeid; Schügerl, Radoslav; Velísková, Yvetta

doi:10.1007/s11269-022-03139-8

Cited by 10 publications

(18 citation statements)

References 31 publications

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“…A relatively dense monitoring network including precipitation, GW and SW level was established in the area regularly surveyed by the Slovak Hydrometeorological Institute. Several studies were dealing with various aspects of SW and GW in this area, such as the quality and quantity of water resources (Červeňanská et al, 2021;Kováčová, 2022;Schügerl, 2019;Schügerl et al, 2021); riverbed silting processes (Dulovičová, 2019); interaction of the canals with the aquifer (Baroková et al, 2017(Baroková et al, , 2020Dušek and Velísková, 2017;Okhravi et al, 2022b) and more.…”

Section: Materials and Methods Study Area -General Overviewmentioning

confidence: 99%

Impacts of riverbed aggradation on groundwater regime in a lowland area

Bara,

Dulovičová,

Velísková

et al. 2024

Journal of Hydrology and Hydromechanics

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In this study, the influence of riverbed silting on the groundwater regime in a lowland area was investigated. The study area is situated at the Rye Island (Žitný Ostrov) in Slovakia, along the Gabčíkovo – Topoľníky canal, which is part of the drainage-irrigation canal system constructed in this locality. The Rye Island is an area with very low slope (0.25 10–4) and good climatic conditions for aquatic vegetation, therefore the canals are influenced by intensive silting processes. The spatial and temporal patterns of surface water – groundwater exchange are significantly influenced by the thickness of riverbed sediments and their permeability. The aim of this study was to evaluate the thickness and hydraulic conductivity of bed sediments in the Gabčíkovo – Topoľníky canal and to examine their influence on the groundwater – surface water interaction in the area. The hydraulic conductivity of the sediments was assessed from undisturbed samples by the falling head method. The obtained data were used for numerical simulations of groundwater heads by the TRIWACO model for different drainage and infiltration resistance conditions in the area of interest. The results of this study can support the planning of canal maintenance.

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Section: Materials and Methods Study Area -General Overviewmentioning

confidence: 99%

Impacts of riverbed aggradation on groundwater regime in a lowland area

Bara,

Dulovičová,

Velísková

et al. 2024

Journal of Hydrology and Hydromechanics

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“…They showed that in the past, the territory of the Danube Plain has operated as a dynamic fluvial system (inland delta) with its anastomosing, migrating, meandering and braided river channel patterns and the development of several fluvial terraces, levees, abandoned channels and aeolian landforms. Okhravi et al (2022) addressed the problem of flow resistance in lowland rivers impacted by distributed aquatic vegetation by hypothesising that a fixed value for the bed roughness coefficient in lowland rivers (mostly sand-bed rivers) is deemed practically questionable in 45 cross-sections in four lowland streams. They showed that bed forms and aquatic vegetation were significant sources of boundary resistance in lowland rivers.…”

Section: Erosion Sediment Transport River Morphology and Hydro-ecologymentioning

confidence: 99%

Interactions of natural and anthropogenic drivers and hydrological processes on local and regional scales: A review of main results of Slovak hydrology from 2019 to 2022

Szolgay,

Miklánek,

Výleta

2023

AHS

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The need to increase understanding of the impacts of changing natural and anthropogenic drivers on hydrological processes on local and regional scales is an essential prerequisite for advancing hydrology and a precondition for solving water resources management tasks. Slovakia exhibits abundant spatial and temporal variability of hydrological processes complicating the generalisation of runoff regimes. Changing climate and recent extreme floods and droughts put additional pressure on improving the observing, monitoring, describing, and modelling of hydrological processes. This paper reviews the response of hydrologic research in Slovakia to these challenges published in international journals from 2019 to 2022. It continues the practice of publishing the review part of the Slovak National Reports to IUGG on behalf of the IAHS (Szolgay, 2003;2007;, which follows the custom of National IUGG Committees to prepare a Quadrennial Report for the IUGG General Assemblies containing comprehensive summaries of national activities in geodesy and geophysics (Szolgay, et al., 2023).

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“…As briefly mentioned earlier, considerable attention has been devoted to understanding the primary sources of boundary resistance, including bedforms and grain sizes, in both lowland and mountainous rivers (Afzalimehr et al, 2010;Ferguson, 2007;Okhravi et al, 2022a;Powell, 2014;Yang et al, 2005). Rivers are typically classified based on their bed gradient and sediment size range.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, sand-bed rivers or low-gradient rivers are characterized by a river bed dominated by sand-size particles (Schügerl et al, 2020;Sulaiman et al, 2017). However, in lowland areas, the presence of aquatic vegetation becomes a significant factor, particularly during the summer season, and must be considered as a resistance source (Cai et al, 2020;Champion and Tanner, 2000;Mewis, 2021;Okhravi et al, 2022a;Song et al, 2014Song et al, , 2017. Among the physical and environmental factors influencing vegetation accumulation in lowland rivers (e.g., river management practices, bed texture, nutrient and light availability, and flow conditions), Franklin et al (2008) emphasized that flow velocity has the most significant impact.…”

Section: Introductionmentioning

confidence: 99%

“…The results provided evidence of the Manning equation's inaccurate predictions of flow resistance in certain conditions, such as steep and small rivers, shallow flows, and the presence of vegetation and bedforms, despite its widespread popularity. For instance, Okhravi et al (2022a) highlighted that the fixed values of n and f are not suitable for mobile river beds (e.g., sand-bed rivers) or lowland rivers that undergo time-dependent changes in vegetation patches along the banks and bed. Previous studies revealed flaws in the Manning and Darcy-Weisbach equations when predicting flow resistance for relative submergence R d 84 ⁄ < 10 (d84 represents the 84% finer grain size) in both types of rivers (Ferguson, 2010;Namaee et al, 2017), particularly in gravel-bed rivers (Ferguson et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Flow resistance at lowland and mountainous rivers

Okhravi,

Alemi,

Afzalimehr

et al. 2023

Journal of Hydrology and Hydromechanics

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This study initially examines the various sources of flow resistance in sand-bed (lowland) and gravel-bed (mountainous) rivers along with the limitations of traditional estimation methods. The nondimensional hydraulic geometry approach, relating dimensionless flow discharge (q *) to the Darcy-Weisbach friction factor (f), has demonstrated good performance for both river types, covering shallow to moderately deep flows. However, accuracy in estimating f is affected by simplifications like assuming uniform and deep flow, neglecting bed load transport and vegetation effects, which require further evaluation. To address these issues, the proposed method is evaluated using data from four sand-bed rivers in Slovakia (with vegetation), and three gravel-bed rivers in Iran (dominated by cobbles and boulders). Bedforms prove to be significant resistance sources in all studied rivers. The approach yields separate predictors for each river type, showing a satisfactory agreement between observed and calculated values within a maximum deviation of ±20% error bands. These predictors are further validated using field data and established equations from rivers with similar physiographic characteristics. Results indicate the method performs well in predicting flow resistance in sand-bed rivers, slightly overestimating overall (+40%). It effectively captures riverbed features and vegetation influence under small-scale roughness conditions. However, the predictor’s validity for gravel-bed rivers is somewhat limited due to high variability in water-surface profiles, making it challenging to accurately capture flow dynamics under large-scale roughness conditions. Addressing complex characteristics of gravel-bed riverbeds, including boulders and local energy extraction, is crucial for improving the estimation of water-surface profile variations and flow resistance using the hydraulic geometry approach.

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Flow Resistance in Lowland Rivers Impacted by Distributed Aquatic Vegetation

Cited by 10 publications

References 31 publications

Impacts of riverbed aggradation on groundwater regime in a lowland area

Impacts of riverbed aggradation on groundwater regime in a lowland area

Interactions of natural and anthropogenic drivers and hydrological processes on local and regional scales: A review of main results of Slovak hydrology from 2019 to 2022

Flow resistance at lowland and mountainous rivers

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