scholarly journals Spatial variability in river sediments and its link with river channel geometry

2006 ◽  
Vol 42 (6) ◽  
Author(s):  
Yoram Rubin ◽  
Ian A. Lunt ◽  
John S. Bridge
Keyword(s):  
Spatial Variability ◽  
River Sediments ◽  
River Channel ◽  
Channel Geometry

scholarly journals River Channel Geometry and Rating Curve Estimation Using Height above the Nearest Drainage

2018 ◽  
Vol 54 (4) ◽  
pp. 785-806 ◽  
Author(s):  
Xing Zheng ◽  
David G. Tarboton ◽  
David R. Maidment ◽  
Yan Y. Liu ◽  
Paola Passalacqua
Keyword(s):  
River Channel ◽  
Rating Curve ◽  
Channel Geometry ◽  
Curve Estimation

scholarly journals Fluvial sediment pathways enlightened by OSL bleaching of river sediments and deltaic deposits

2018 ◽  
Author(s):  
Elizabeth Chamberlain ◽  
Jakob Wallinga
Keyword(s):  
Mississippi River ◽  
Mississippi Delta ◽  
River Sediments ◽  
River Channel ◽  
Spatiotemporal Pattern ◽  
Channel Networks ◽  
Optical Signals ◽  
Meandering Channel ◽  
Channel Belt ◽  
Mouth Bar

Abstract. While a number of studies have investigated bleaching of the optical signals of sediments in rivers and deltas, unified trends and mechanisms for bleaching in these settings remain unresolved. Here, we explore the bleaching of the optically stimulated luminescence (OSL) signal of quartz sediments in a large fluviodeltaic system across time and space, by comparing residual doses of sand and silt from the modern Mississippi River channel with estimated residual doses of sand isolated from Late Holocene Mississippi Delta mouth bar and overbank deposits. Further insight is obtained from a comparison of burial ages of paired quartz sand and silt of Mississippi Delta overbank deposits. Contrasting some previous investigations, we find that the bleaching of the OSL signal is at least as likely for finer sediment as for coarser sediment of the meandering Mississippi River and its delta. In addition we find an unexpected spatiotemporal pattern in OSL bleaching of mouth bar sand deposits. We suggest this may be caused by changes in upstream pathways of the meandering channel belt(s) within the alluvial valley, or by distributary channel and coastal dynamics within the delta. Our study demonstrates that the degree of OSL bleaching of sand in a large delta can be highly time- and/or space-dependent. Silt is shown to be generally sufficiently bleached in both the modern Mississippi River and associated paleo-deposits regardless of age, and may provide a viable option for obtaining OSL chronologies in megadeltas. In addition to informing dating approaches, our work contributes to initiatives to use luminescence signals to fingerprint sediment pathways within river channel networks and their deltas.

scholarly journals Quantifying the combined effects of multiple extreme floods on river channel geometry and on flood hazards

2016 ◽  
Vol 538 ◽  
pp. 256-268 ◽  
Author(s):  
Mingfu Guan ◽  
Jonathan L. Carrivick ◽  
Nigel G. Wright ◽  
P. Andy Sleigh ◽  
Kate E.H. Staines
Keyword(s):  
River Channel ◽  
Combined Effects ◽  
Flood Hazards ◽  
Channel Geometry ◽  
Extreme Floods

Prediction of organic matter degradability in river sediments

2020 ◽  
Author(s):  
Julia Gebert ◽  
Florian Zander
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Spatial Variability ◽  
River Sediments ◽  
Redox Conditions ◽  
Time Dependent ◽  
Anaerobic Conditions ◽  
Short Term ◽  
Aerobic And Anaerobic

<p>Under anaerobic conditions, degradation of organic matter in river sediments leads to gas formation, with organic carbon being released mainly as CH<sub>4</sub> and CO<sub>2</sub>. Gas bubbles reduce sediment density, viscosity and shear strength, impede sonic depth finding and are suspected to affect the sediments’ rheological properties. Moreover, methane (CH<sub>4</sub>) is a potent greenhouse gas with a global warming potential (GWP<sub>100</sub>) of 28-36. Therefore, the climate impact may vary greatly depending on the way sediments are managed (for example, type and frequency of dredging and relocation in the water body or treatment on land). The objective of this paper is therefore to quantify the time-dependent stability, or inversely, the lability of sediment organic matter (SOM) as a basis for prediction of effects on sediment mechanical properties and on the release of greenhouse gases.</p><p>Within two years, over 200 samples of predominantly fine-grained sediment were collected from nine locations within a 30 km transect through the Port of Hamburg. All samples were, amongst other analyses, subjected to long-term (> 250 days) aerobic and anaerobic incubation for measurement of SOM degradation, yielding a comprehensive data set on the time-dependent change in degradation rates and the corresponding size of differently degradable SOM pools. SOM degradability exhibited a pronounced spatial variability with an approximately tenfold higher anaerobic and a roughly fivefold higher aerobic degradability of upstream SOM compared to downstream SOM. Lower δ<sup>13</sup>C values, higher DNA concentrations and a higher share of organic carbon in the light density fraction as well as elevated chlorophyll concentrations in the water phase support the hypothesis of increased biological sources of SOM at upstream locations and increased SOM degradability in shallow compared to deep layers (Zander et al., 2020).</p><p>First statistical and time series analyses indicate that</p><ul><li>Long-term SOM lability appears to be predictable from short-term measurements.</li> <li>The relationship between short-term and long-term SOM degradation is site-specific and also differs for layers of different age (depth). This supports the above-mentioned variability between sites regarding the size of differently degradable carbon pools, as well as for the depth profile at any one site.</li> <li>The relevance of the available electron acceptors (redox conditions) for SOM degradation, i.e. the ratio between carbon release under aerobic and anaerobic conditions, differs less by site but more so by layers of different age (depth). This is plausible as especially the top layers are exposed to more variability in redox conditions than the deeper layers that are always under reducing conditions.</li> </ul><p>Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments, accepted for publication.</p>

scholarly journals Modeling surface water dynamics in the Amazon Basin using MOSART-Inundation v1.0: impacts of geomorphological parameters and river flow representation

2017 ◽  
Vol 10 (3) ◽  
pp. 1233-1259 ◽  
Author(s):  
Xiangyu Luo ◽  
Hong-Yi Li ◽  
L. Ruby Leung ◽  
Teklu K. Tesfa ◽  
Augusto Getirana ◽  
...  
Keyword(s):  
Surface Water ◽  
Spatial Variability ◽  
Amazon Basin ◽  
River Flow ◽  
Water Dynamics ◽  
Surface Hydrology ◽  
Channel Geometry ◽  
Vegetation Height ◽  
Floodplain Inundation ◽  
Manning Roughness

Abstract. In the Amazon Basin, floodplain inundation is a key component of surface water dynamics and plays an important role in water, energy and carbon cycles. The Model for Scale Adaptive River Transport (MOSART) was extended with a macroscale inundation scheme for representing floodplain inundation. The extended model, named MOSART-Inundation, was used to simulate surface hydrology of the entire Amazon Basin. Previous hydrologic modeling studies in the Amazon Basin identified and addressed a few challenges in simulating surface hydrology of this basin, including uncertainties of floodplain topography and channel geometry, and the representation of river flow in reaches with mild slopes. This study further addressed four aspects of these challenges. First, the spatial variability of vegetation-caused biases embedded in the HydroSHEDS digital elevation model (DEM) data was explicitly addressed. A vegetation height map of about 1 km resolution and a land cover dataset of about 90 m resolution were used in a DEM correction procedure that resulted in an average elevation reduction of 13.2 m for the entire basin and led to evident changes in the floodplain topography. Second, basin-wide empirical formulae for channel cross-sectional dimensions were refined for various subregions to improve the representation of spatial variability in channel geometry. Third, the channel Manning roughness coefficient was allowed to vary with the channel depth, as the effect of riverbed resistance on river flow generally declines with increasing river size. Lastly, backwater effects were accounted for to better represent river flow in mild-slope reaches. The model was evaluated against in situ streamflow records and remotely sensed Envisat altimetry data and Global Inundation Extent from Multi-Satellites (GIEMS) inundation data. In a sensitivity study, seven simulations were compared to evaluate the impacts of the five modeling aspects addressed in this study. The comparisons showed that representing floodplain inundation could significantly improve the simulated streamflow and river stages. Refining floodplain topography, channel geometry and Manning roughness coefficients, as well as accounting for backwater effects had notable impacts on the simulated surface water dynamics in the Amazon Basin. The understanding obtained in this study could be helpful in improving modeling of surface hydrology in basins with evident inundation, especially at regional to continental scales.

Observations of riverbed scour under a developing hanging ice dam

2006 ◽  
Vol 33 (2) ◽  
pp. 214-218 ◽  
Author(s):  
Jueyi Sui ◽  
Faye E Hicks ◽  
Brian Menounos
Keyword(s):  
Yellow River ◽  
River Channel ◽  
River Ice ◽  
The Yellow River ◽  
Channel Geometry ◽  
Ice Accumulation ◽  
Field Investigations ◽  
Gauging Station

This paper illustrates the importance of river ice accumulations in changing river channel geometry based on field investigations carried out at the Hequ gauging station on the Yellow River in China. A relationship is established between riverbed deformation and ice accumulation.Key words: river ice, hanging dam, ice accumulation, river scour, Yellow River.

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