Estimation of roughness coefficients for natural stream channels with vegetated banks

Coon, William F.

doi:10.3133/wsp2441

Cited by 17 publications

(6 citation statements)

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“…The impact of vegetation on flow conditions is complex, as it depends on the density and height of the vegetation, on its phenological phase, morphological and structural characteristics (Chow, 1959;Wang et al, 2015;Vargas-Luna et al, 2015). Vegetation density is primarily determined by the species (Antonarakis et al, 2010), the number and rigidity of stems (Freeman et al, 2000;Galema, 2009), and the density of foliage (Ree and Crow, 1977;Järvelä, 2004;Antonarakis et al, 2010), thus it can vary by season (Burkham, 1976;Coon, 1998). The denser vegetation and more rigid stems create greater obstructions to flood flow, resulting in reduced flow velocity.…”

Section: Introductionmentioning

confidence: 99%

Changes in Floodplain Vegetation Density and the Impact of Invasive Amorpha fruticosa on Flood Conveyance

Nagy

Kiss

Fehérváry³

et al. 2018

Journal of Environmental Geography

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Flood conveyance of floodplains is significantly influenced by the riparian vegetation cover, since vegetation affects flow velocity, therefore has a considerable impact on flood height and rate and pattern of sedimentation. However, climate change promotes the spread of invasive species, and their rapid growth results in dense vegetation stands, thus they have a significant impact on floodwater hydraulics. The aims of the present study are (1) to analyse the long-term changes in land-use and vegetation density on the Lower Tisza River, (2) to evaluate the role of the invasive Amorpha fruticosa in increasing vegetation density, and (3) to model the effect of dense floodplain vegetation on flood level and flood conveyance. Long-term (1784-2017) changes of land-use suggest that in natural conditions the study area was occupied by wetlands (92%), thus water covered the area for almost the whole year. In the 19th century, after levee constructions the wetlands were replaced by meadows and pastures (94%), then by the end of the 20th century planted and riparian forests replaced these land-covers. As a result, the mean roughness (0.14) of the floodplain has increased threefold until the early 21st century. Today forests are invaded by Amorpha fruticosa, which increases the vegetation density by 3% in riparian forests, by 23% in forest plantations, and by up to 100% in abandoned pastures and a rable lands. According to the results of HEC-RAS (Hydrologic Engineering Center’s River Analysis System) and CES (Conveyance Estimation System) models, if floodplain vegetation was managed and Amorpha fruticosa was cleared from the floodplain, peak flood level would decrease by 15 cm. Due to dense vegetation, the flood conveyance decreased by 4-6%, and the presence of Amorpha fruticosa reduced the flood flow velocities by 0.014-0.016 m/s. Accordingly, clearance of the floodplain from Amorpha fruticosa would have positive effects on flood protection, since peak flood stages would decrease and flood waves would shorten.

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Section: Introductionmentioning

confidence: 99%

Changes in Floodplain Vegetation Density and the Impact of Invasive Amorpha fruticosa on Flood Conveyance

Nagy

Kiss

Fehérváry³

et al. 2018

Journal of Environmental Geography

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“…Anyway, the distributions of flow velocity are significantly affected by the rigid submerged vegetation of different vegetation heights or relative submergences. A problem that cannot be ignored is that high-velocity water flow may erode the river bed and banks (Coon, 1998;Qian et al, 2016). As reported in previous studies, vegetation patches planted properly will help to better protect against such erosion (Liu et al, 2017).…”

Section: Effects Of Vegetation Height and Relative Submergence On Flo...mentioning

confidence: 90%

Effects of vegetation height and relative submergence for rigid submerged vegetation on flow structure in open channel

Wang

Zhang

et al. 2022

Earth sci. res. j.

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In this research, the vegetation height and a concept of relative submergence are adapted to experimentally investigate the effects of rigid submerged vegetation on flow structure. The results reveal that the relative submergence presents decreasing trend along the submerged vegetation section and the average relative submergence follows a power functional decreasing relationship regarding to the increase of vegetation height. After the exit of vegetation block, the water depths for the vegetated cases resume to the level and trend of the case without vegetation. The differences between the maximum and minimum water depths for the submerged cases follow a linear relationship with vegetation height and a negative power functional relationship with the average relative submergence, with which, the raised water depths due to rigid submerged vegetation can be predicted under similar hydraulic and vegetation conditions to the present research. Due to the retardance of vegetation block, the differences between the maximum and minimum flow velocities increase with the vegetation height as the maximum values change slightly and the minimum values decrease continuously. The findings of the research may improve the comprehensive understandings of open channel hydraulic behaviors affected by rigid submerged vegetation and give some guidance to the river ecological restorations.

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“…The friction of the river channel to a given flow is determined by Manning's roughness coefficient (Coon, 1998), which is dependent on land use and land cover (LULC) and the roughness of the sediment load of the modeling river channel in the study area. In the study, the value of Manning's N of crosssections was obtained from the GLC10 LULC product (http:// data.ess.tsinghua.edu.cn/fromglc10_2017v01.html) with a spatial resolution of 10 m. The extent to which all transect widths had covered along the river channel was recorded for the analysis of LULC types in this region.…”

Section: Lulc and Manning's Nmentioning

confidence: 99%

Change of moraine-dammed glacial lakes and simulation of glacial lake outburst flood in the Yi’ong Zangbo River basin

et al. 2022

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Glacial lake outburst floods (GLOFs) are a serious potential threat to the safety of life and property in downstream areas. In this study, moraine-dammed glacial lakes in the Yi’ong Zangbo River basin were recognized based on Landsat ETM+/TM/OLI images in 2000 and 2019. Also, GLOFs for the Jionglaco, the largest glacial lake in this basin, were simulated using the one-dimensional hydrodynamic model. The results show that the total number and area of moraine-dammed glacial lakes in this basin increased by 10 (10.52%) and 5.49 km2 (48.24%) from 2000 to 2019, respectively, in which the area of the Jionglaco increased by 3.22 km2. The peak discharge at the breach outlet for five scenarios with different combinations of breach width (80 and 120 m), depth (2.5 and 5 m), and flood time (1.5 and 3 h) are 489 , 1,327.43, 444.32, 617.47, and 1,570.61 m3/s. With the addition of baseflow in the river, the peak discharge at bridge site 15,138.93 km from Jionglaco, is 1,040.89, 1,724.00, 1,024.85, 1,162.25, and 1,990.52 m3/s. The combination of baseflow in river and the GLOF discharge results in an increasing peak discharge in the further downstream region. However, the arrival of peak discharge in downstream areas is delayed, which increases the chances of people escaping.

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Estimation of roughness coefficients for natural stream channels with vegetated banks

Cited by 17 publications

References 1 publication

Changes in Floodplain Vegetation Density and the Impact of Invasive Amorpha fruticosa on Flood Conveyance

Changes in Floodplain Vegetation Density and the Impact of Invasive Amorpha fruticosa on Flood Conveyance

Effects of vegetation height and relative submergence for rigid submerged vegetation on flow structure in open channel

Change of moraine-dammed glacial lakes and simulation of glacial lake outburst flood in the Yi’ong Zangbo River basin

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