scholarly journals The impact of inter‐flood duration on non‐cohesive sediment bed stability

2019 ◽  
Vol 44 (14) ◽  
pp. 2861-2871 ◽  
Author(s):  
Annie Ockelford ◽  
Stephen Woodcock ◽  
Heather Haynes
Keyword(s):  
Cohesive Sediment ◽  
Flood Duration ◽  
Sediment Bed ◽  
Bed Stability ◽  
The Impact

scholarly journals Effect of Gate Selection on the Non-Cohesive Sedimentation in Irrigation Schemes

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2765
Author(s):  
Shaimaa Theol ◽  
Bert Jagers ◽  
Jigyasha Rai Yangkhurung ◽  
F.X. Suryadi ◽  
Charlotte de Fraiture
Keyword(s):  
Cohesive Sediment ◽  
Sediment Deposition ◽  
Hydraulic Parameters ◽  
Crop Water ◽  
Gate Operation ◽  
Control Structures ◽  
Sediment Removal ◽  
1D Model ◽  
The Impact ◽  
Selection Of

In order to cover the crop water requirements, flow control structures such as gates and weirs are used to transfer the desired amount of water from the canals to the field canals. This paper examines the impact of gate operation and the selection of gates on the deposition of non-cohesive sediment. The Delft3D model is used to simulate the effects of different scenarios regarding gate operation and the location of the gate that is opened. The model results showed that the gate selection affects not only hydraulic parameters but also morphological parameters. It was found that opening the gates closer to the offtake resulted in less sediment deposition at the entrance of the branch canal when compared to opening the gates further away. Gate selection can be used as a tool in sediment management. By alternating the opening of different gates sediments that are already deposited after opening one gate can be eroded when another gate is operated, thus minimizing the additional cost of sediment removal. The use of Delft3D proved beneficial as the selection of different gates leads to asymmetric sediment deposition patterns which would be missed when using a 1D model.

Local scour around abutment in clay/sand-mixed cohesive sediment bed

2013 ◽  
Vol 20 (1) ◽  
pp. 46-64 ◽  
Author(s):  
Koustuv Debnath ◽  
Susanta Chaudhuri ◽  
Mrinal K. Manik
Keyword(s):  
Cohesive Sediment ◽  
Local Scour ◽  
Sediment Bed

scholarly journals Study on the influence of infiltration on flood propagation with different peak shape coefficients and duration

Water Policy ◽  
2021 ◽  
Author(s):  
Jingming Hou ◽  
Zhaoan Zhang ◽  
Dawei Zhang ◽  
Baoshan Shi ◽  
Guangzhao Chen ◽  
...  
Keyword(s):  
Northern China ◽  
Peak Shape ◽  
Maximum Difference ◽  
Soil Infiltration ◽  
Discharge Data ◽  
Considerable Uncertainty ◽  
Flood Duration ◽  
Inundation Area ◽  
Flood Simulations ◽  
The Impact

Abstract Traditional flood simulations fail to properly consider the impact of soil infiltration in floodplain areas with high soil infiltration rates. Notably, ignoring soil infiltration will lead to considerable uncertainty in flood simulations. In this paper, a fully hydrodynamic model coupled with the Green–Ampt infiltration model was used. Taking a natural reach in northern China (HTH in this paper) as a case study, observed flood discharge data were used to analyze the influence of soil infiltration on flood propagation based on the flood propagation simulation results for various inflow conditions. The maximum difference of inundation area is about 25%. The results show that soil infiltration has little effect on the inundation area during the rising stage of a flood. In the late period of a flood, the inundation area considering the effect of infiltration is smaller than that without infiltration, and the smaller the peak coefficient is, the longer the flood duration is, the larger the impact of infiltration on the inundation area. When the peak shape coefficient is 0.42 and the flood duration is 44.4 h, the maximum difference of the inundation area is about 28%. The research results provide a reference for flood management and post-disaster rescue efforts.

Analysis of tidal average saturated suspended sediment concentration of cohesive sediment in the Yangtze Estuary

2021 ◽  
Author(s):  
Junyu Tao ◽  
Peng Hu ◽  
Wei Li ◽  
Zhiguo He
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Cohesive Sediment ◽  
Yangtze Estuary ◽  
Shear Stresses ◽  
The Yangtze Estuary ◽  
Erosion And Deposition ◽  
Deposition Fluxes ◽  
The Impact

<p>It is generally believed that sediment erosion and deposition can’t occur simultaneously, which is also reflected in the classical Partheniades-Krone formulas used to calculate erosion and deposition flux. In this study, the erosion and deposition fluxes of cohesive sediment are integrated in the tidal period respectively, and when they are equal, the corresponding suspended cohesive sediment concentration is called ‘tidal average saturated concentration of cohesive sediment’. Theoretical analysis of the factors affecting the saturated concentration indicates that a large erosion coefficient results in a high saturated concentration level. The corresponding critical erosion and deposition shear stresses (i.e., τ<sub>e </sub>and τ<sub>d</sub>) at saturated concentration have many possibilities. Therefore, it is understandable that good agreement of suspended sediment concentration between simulation and observation have been obtained by adjusting τ<sub>e </sub>and τ<sub>d </sub>in the previous numerical simulation calibration. According to the relative magnitude of τ<sub>e </sub>and τ<sub>d</sub> at saturated concentration, the erosion and deposition fluxes of cohesive sediment can be divided into four situations: weak erosion (i.e., τ<sub>e  ></sub> τ<sub>d</sub>), intense erosion (i.e., τ<sub>e  <</sub> τ<sub>d</sub>), intense deposition (i.e., τ<sub>e  <</sub> τ<sub>d</sub>), and weak deposition (i.e., τ<sub>e > </sub>τ<sub>d</sub> ). A two-dimensional numerical model is applied to calculate the temporal and spatial variation of the saturated concentration of cohesive sediment in the Yangtze Estuary. Simulation results shows the following findings. 1) The impact of the fraction of the kth size class in the surface (top) layer of bed material on erosion flux of non-uniform cohesive sediment is necessary to be considered. Otherwise, the calculated saturated concentration of cohesive sediment is greater than the measured. 2) The differences between saturated concentration and the field calculated/measured suspended sediment concentration can be applied to infer bed erosion/deposition characteristics to some extent, and compared it with the measured erosion/deposition result, which in turn verifies the values of  τ<sub>e </sub>and τ<sub>d</sub> in the model. This finding provides insights for the following research on transport and diffusion of cohesive sediment in estuary and coastal areas.</p>

Maximum flood depth characterizes above-ground biomass in African seasonally shallowly flooded grasslands

2007 ◽  
Vol 23 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Paul Scholte
Keyword(s):  
Dry Season ◽  
Perennial Grasses ◽  
Individual Species ◽  
Above Ground Biomass ◽  
Nutrient Quality ◽  
Flood Duration ◽  
Ground Biomass ◽  
Flood Depth ◽  
The Individual ◽  
The Impact

Flood depth has been frequently used to explain the distribution of plant species in seasonally flooded grasslands, but its relation with vegetation production has remained ambiguous. The relationship between flooding and above-ground biomass at the end of the flooding season and during the dry season was studied to assess the impact of reflooding on the Logone floodplain, Cameroon. Above-ground biomass of a combination of all species and of the individual perennial grasses Oryza longistaminata and Echinochloa pyramidalis showed a positive linear relationship with maximum flood depth up to 1 m. The gradient of these relationships became steeper and their fit better during the 2 y following the installation of the flooding, showing the response lag to floodplain rehabilitation. Flood duration only explained the above-ground biomass of the combination of all species and not of the individual species. Above-ground biomass data from other floodplains in the three main African geographic regions showed a similar relationship with maximum flood depth less than 1 m. Dry-season regrowth, important because of its high nutrient quality during forage scarcity, was not directly related to maximum flood depth, possibly because of its dependency on the period of burning and soil moisture. Presented data indicate that a rise of water level of 1 cm corresponds to an increase in above-ground biomass of c. 150 kg DM ha−1.

scholarly journals Cohesive and mixed sediment in the Regional Ocean Modeling System (ROMS v3.6) implemented in the Coupled Ocean Atmosphere Wave Sediment-Transport Modeling System (COAWST r1179)

2017 ◽  
Author(s):  
Christopher R. Sherwood ◽  
Alfredo L. Aretxabaleta ◽  
Courtney K. Harris ◽  
J. Paul Rinehimer ◽  
Romaric Verney ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Cohesive Sediment ◽  
Ocean Modeling ◽  
Transport Modeling ◽  
Regional Ocean Modeling System ◽  
Fine Grained ◽  
Sediment Bed ◽  
Ocean Atmosphere ◽  
Mixed Sediment ◽  
Floc Characteristics

Abstract. We describe and demonstrate algorithms for treating cohesive and mixed sediment that have been added to the Regional Ocean Modeling System (ROMS version 3.6), as implemented in the Coupled Ocean Atmosphere Wave Sediment-Transport Modeling System (COAWST Subversion repository revision 1179). These include: floc dynamics (aggregation and disaggregation in the water column); changes in floc characteristics in the seabed; erosion and deposition of cohesive and mixed (combination of cohesive and non-cohesive) sediment; and biodiffusive mixing of bed sediment. These routines supplement existing non-cohesive sediment modules, thereby increasing our ability to model fine-grained and mixed-sediment environments. Additionally, we describe changes to the sediment bed-layering scheme that improve the fidelity of the modeled stratigraphic record. Finally, we provide examples of these modules implemented in idealized test cases and a realistic application.

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