scholarly journals MORPHOLOGICAL HYSTERESIS OF ARTIFICIAL BEACH UNDER LARGE WAVE CONDITION: AN EXPERIMENTAL INVESTIGATION

Author(s):  
Yuan Li ◽  
Chi Zhang

Submerged Artificial sandBars (SAB) are usually implemented on the lower shoreface to protect berms or dunes during storm surges. The lee-effect of SAB is due to its ability in triggering large wave breaking, so that sediment concentration in water column and sediment transport capacity will decrease in the covered areas. Previous studies analyzed the lee-effect and topography evolution of SAB, however the morphological coupling of SAB and natural profiles is seldom referred. In this study, the morphological coupling between SAB located on the lower shoreface and the berm in upper beach is investigated in a well-controlled physical experiment.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/KsOK30StZZQ

Author(s):  
Peng Hu ◽  
Liming Tan ◽  
Jiafeng Xie ◽  
Zhiguo He

Swash sediment transport and beach deformation has received great attention in the past two decades. Quantification of swash-induced sediment transport rate is of vital importance for accurate prediction of beach deformation in the swash zone. Two empirical parameters are involved in this quantification, empirical relations for sediment transport capacity and the bed shear stress that may be used in the former. Since the swash zone is highly unsteady, of short cross-shore distance, sediment transport in this zone may be of high possibility to be lag of the flow variation. Thus we have firstly developed a non-capacity sediment transport model for the swash zone. This model appreciates the fact that the actual sediment transport rate may not be necessarily equal to the sediment transport capacity of the flow. In contrast to traditional capacity models that calculate sediment transport rate using directly empirical relations (Hu et al. 2015), the non-capacity model uses the advection-diffusion equation to calculate depth-averaged sediment concentration firstly, and afterwards compute sediment transport rate as flow depth*velocity*concentration. We have also noted that some empirical relations for sediment transport capacity may predict physically unrealistic high values of sediment concentration in the swash zone. This is attributed to the vanishing water depth in the swash zone, whereas existing empirical relations are developed for relatively large water depths (Hu et al. 2015; Li et al. 2017).


Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3054
Author(s):  
Linh Nguyen Van ◽  
Xuan-Hien Le ◽  
Giang V. Nguyen ◽  
Minho Yeon ◽  
Sungho Jung ◽  
...  

Estimation of sediment transport capacity (STC) plays a crucial role in simulating soil erosion using any physics-based models. In this research, we aim to investigate the pros and cons of six popular STC methods (namely, Shear velocity, Kilinc-Richardson (KR), Effective stream power, Slope and unit discharge, Englund-Hansen (EH), and Unit stream power) for soil erosion/deposition simulation at watershed scales. An in-depth analysis was performed using the selected STC methods integrated into the Grid Surface Subsurface Hydrologic Analysis model for investigating the changes in morphology at spatial-temporal scales at the Cheoncheon watershed, South Korea, over three storm events. Conclusions were drawn as follows. (1) Due to the ability of the KR and EH methods to include an additional parameter (i.e., erodibility coefficient), they outperformed others by producing more accurate simulation results of sediment concentration predictions. The KR method also proved to be superior to the EH method when it showed a more suitable for sediment concentration simulations with a wide range of sediment size and forcing magnitude. (2) We further selected 2 STC methods among the 6 methods to deeply explore the spatial distribution of erosion/deposition. The overall results were more agreeable. For instance, the phenomenon of erosion mainly occurred upstream of watersheds with steep slopes and unbalanced initial sediment concentrations, whereas deposition typically appeared at locations with flat terrain (or along the mainstream). The EH method demonstrated the influence of topography (e.g., gradient slope) on accretionary erosion/deposition results more significantly than the KR method. The obtained results contribute a new understanding of rainfall-sediment-runoff processes and provide fundamental plans for soil conservation in watersheds.


Geoderma ◽  
2019 ◽  
Vol 337 ◽  
pp. 384-393 ◽  
Author(s):  
Hongli Mu ◽  
Xianju Yu ◽  
Suhua Fu ◽  
Bofu Yu ◽  
Yingna Liu ◽  
...  

2012 ◽  
Vol 16 (2) ◽  
pp. 591-601 ◽  
Author(s):  
M. Ali ◽  
G. Sterk ◽  
M. Seeger ◽  
M. Boersema ◽  
P. Peters

Abstract. Sediment transport is an important component of the soil erosion process, which depends on several hydraulic parameters like unit discharge, mean flow velocity, and slope gradient. In most of the previous studies, the impact of these hydraulic parameters on transport capacity was studied for non-erodible bed conditions. Hence, this study aimed to examine the influence of unit discharge, mean flow velocity and slope gradient on sediment transport capacity for erodible beds and also to investigate the relationship between transport capacity and composite force predictors, i.e. shear stress, stream power, unit stream power and effective stream power. In order to accomplish the objectives, experiments were carried out in a 3.0 m long and 0.5 m wide flume using four well sorted sands (0.230, 0.536, 0.719, 1.022 mm). Unit discharges ranging from 0.07 to 2.07 × 10−3 m2 s−1 were simulated inside the flume at four slopes (5.2, 8.7, 13.2 and 17.6%) to analyze their impact on sediment transport rate. The sediment transport rate measured at the bottom end of the flume by taking water and sediment samples was considered equal to sediment transport capacity, because the selected flume length of 3.0 m was found sufficient to reach the transport capacity. The experimental result reveals that the slope gradient has a stronger impact on transport capacity than unit discharge and mean flow velocity due to the fact that the tangential component of gravity force increases with slope gradient. Our results show that unit stream power is an optimal composite force predictor for estimating transport capacity. Stream power and effective stream power can also be successfully related to the transport capacity, however the relations are strongly dependent on grain size. Shear stress showed poor performance, because part of shear stress is dissipated by bed irregularities, bed form evolution and sediment detachment. An empirical transport capacity equation was derived, which illustrates that transport capacity can be predicted from median grain size, total discharge and slope gradient.


1989 ◽  
Vol 32 (5) ◽  
pp. 1545-1550 ◽  
Author(s):  
S. C. Finkner ◽  
M. A. Hearing ◽  
G. R. Foster ◽  
J. E. Gilley

Sign in / Sign up

Export Citation Format

Share Document