scholarly journals AN EXPERIMENTAL STUDY ON SAND DUNE SEDIMENT TRANSPORT DUE TO TSUNAMI OVERWASH

2017 ◽  
pp. 15
Author(s):  
K M Ahtesham Hossain Raju ◽  
Shinji Sato
Keyword(s):  
Experimental Study ◽  
Sediment Transport ◽  
Mathematical Models ◽  
Storm Surge ◽  
Laboratory Study ◽  
Sand Dune ◽  
Small Scale ◽  
Data Set ◽  
Grain Sizes ◽  
Dry Sand

Response of sand dune when overwashed by tsunami or storm surge, is investigated by conducting small scale laboratory study. Dune consisting of initially wet sand and initially dry sand are tested for three different sand grain sizes. Overtopping of water and the corresponding sediment transport are analyzed. These data set can be used to validate mathematical models associated with dune sediment transport as well as prediction of dune profile.

Evaluation of CCHE2D hydrodynamic and sediment transport model to simulate erosional sources in row crop agriculture in Midwest US

2020 ◽  
Author(s):  
Robert Wells ◽  
Yafei Jia ◽  
Henrique Momm ◽  
Carlos Castillo ◽  
Dalmo Vieira ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Soil Loss ◽  
Transport Model ◽  
Landscape Evolution ◽  
Small Scale ◽  
Agricultural Fields ◽  
Data Set ◽  
Sediment Transport Model ◽  
Total Soil ◽  
Physically Based

<p>Soil erosion due to rainfall and overland flow can be detrimental to agricultural management and long-term agricultural sustainability. Although numerous conservation measures and planning strategies have greatly reduced the amount of sediment moving within the landscape, there are still unresolved questions concerning initiation of particle motion, susceptibility to erosion, total soil loss, sediment transport and general measurement theory. Within agricultural fields, ephemeral erosion is particularly harmful because these sources can accelerate sediment transport, often yield more sediment than interrill sources and are more challenging to mitigate. In this study, terrain data were collected by aerial photogrammetry using an unmanned aerial system (UAS) following planting and approximately one month later, while climate variables during the period were collected using NexRad radar. Imagery was captured within seven agricultural fields (six in Iowa and one in Minnesota), ranging in size from 0.6 to 3.6 hectare (1.6 to 8.8 acre). Considering the small scale in topographic variation between two surveys, extreme efforts were applied to image processing and geospatial registration. Advanced models for camera calibration utilizing Micmac open-source photogrammetry software package were used to account for complex distortion patterns in the raw image data set. The undistorted images were then processed using Agisoft Photoscan for camera alignment, model georeferencing and dense point cloud generation (millions to billions of points per survey), from which digital elevation models (DEMs; 10 to 57 million cells) were produced. A physically-based finite element hydrodynamic and sediment transport model (CCHE2D, developed at the National Center for Computational Hydroscience and Engineering) was applied to simulate hydrological (runoff), sediment detachment (raindrop splash, sheet flow, and concentrated flow erosion) and sediment transport/deposition landscape evolution processes. Simulated geomorphological and sediment budget results over time were compared to field observations for model input parameter adjustment and consequently quantification of estimates. Integration of high-resolution spatial and temporal topographic measurements with physically-based numerical models support the development and validation of dynamic landscape evolution models needed for accurate prediction and quantification of gully initiation, evolution and impact on total soil loss and effective conservation management planning.</p>

Quantification of biogeomorphic interactions between small-scale sediment transport and primary succession in the Gepatschferner glacier foreland, Austria

2020 ◽  
Author(s):  
Stefan Haselberger ◽  
Lisa Maria Ohler ◽  
Robert R. Junker ◽  
Jan-Christoph Otto ◽  
Sabine Kraushaar
Keyword(s):  
Sediment Transport ◽  
Primary Succession ◽  
Initial Conditions ◽  
Ecological Succession ◽  
Qualitative Description ◽  
Small Scale ◽  
Successional Stage ◽  
Data Set ◽  
Relative Dating ◽  
Glacier Foreland

<p>Landscape change is an interplay of abiotic and biotic processes with bi-directional and interwoven relationships. Glacier foreland areas can act as open-air laboratory to observe biogeomorphic interactions. Paraglacial adjustment establishes initial conditions for ecological succession and requires constant feedbacks between plants and landscapes. Frequency and magnitude of geomorphic processes and functional composition and abundance of plants govern these responses. Up to now, biogeomorphic studies have mainly focused on the qualitative description of the relationship between biotic and abiotic processes. However, in order to test biogeomorphic concepts, it is necessary to jointly quantify (i) geomorphic process rates as a function of vegetation and (ii) successional development as a function of geomorphic conditions.</p><p>The proglacial area of the Gepatschferner (Kaunertal) in the crystalline Central Eastern Alps presents a showcase environment to investigate these interactions as the retreating glacier and highly active slope processes provide the ground for different stages of ecological succession and promotes high rates of sediment reworking within the proglacial deposits.</p><p>In this particular study, we investigate small-scale biogeomorphic interactions at 30 test sites of 2*3m size. Experimental plots are established on slopes along an ecological succession gradient that reflect different stages of erosion-vegetation interaction. To cover the abiotic condition for the plot sites morphometric characteristics and edaphic variables were determined. In order to quantify abiotic process rates, we use mechanical measurements (i.e. erosion plots) to determine sediment yield and to measure the effect of vegetation on particle size distribution. Relative Dating, historical image analysis and knowledge of glacial retreat helped to estimate time since last perturbation. A detailed vegetation survey was carried out to capture biotic conditions at the sites. Species distribution and abundance at each site, as well as plant functional types provide information on successional stage and functional diversity.</p><p>This data set provides a vital opportunity to test conceptual models on biogeomorphic succession in glacier forelands and to evaluate the bi-directional influence of primary succession on small-scale sediment transport and vice versa.</p>

LABORATORY EXPERIMENTS ABOUT BED PATTERNS IN THE SHOALING REGION UNDER REGULAR WAVES AND REFLECTING CONDITIONS

2017 ◽  
pp. 25
Author(s):  
Manuel Cobos ◽  
María Clavero ◽  
Sandro Longo ◽  
Asunción Baquerizo ◽  
Miguel Angel Losada
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Sediment Transport ◽  
Laboratory Experiments ◽  
Breaking Waves ◽  
Spatial Modulation ◽  
Small Scale ◽  
Growth Mechanisms ◽  
Free Surface Elevation ◽  
Regular Waves

This research is an experimental study of ripple dynamic for regular waves propagating on horizontal and sloping beds in mid- and high-reflective conditions. Small-scale laboratory experiments were carried out on shoaling region (with non breaking waves) and sediment transport in bedload regime. Our experiments showed the key role that plays the reflection in ripple development. The spatial modulation of the free surface elevation due to reflection created sandbars. Ripples grew up in the region where sandbars were appearing. These patterns were gradually reproduced from breakwater to offshore. The incidence of sandbar created a bi-modal structure of ripple geometry. The larger ripples appeared in the crest of sandbars whereas smaller ripples were found in the troughs. Furthermore, it was found that the evolution of ripples at these two locations can be explained by means of different growth mechanisms. Finally, at equilibrium stages, ripple height converges reaching the same height along the sandbar while ripple length and steepness remains almost constant.

scholarly journals Dark energy survey internal consistency tests of the joint cosmological probes analysis with posterior predictive distributions

2021 ◽  
Vol 503 (2) ◽  
pp. 2688-2705
Author(s):  
C Doux ◽  
E Baxter ◽  
P Lemos ◽  
C Chang ◽  
A Alarcon ◽  
...  
Keyword(s):  
Dark Energy ◽  
Internal Consistency ◽  
Goodness Of Fit ◽  
Small Scale ◽  
P Value ◽  
Posterior Predictive Distribution ◽  
Data Set ◽  
Dark Energy Survey ◽  
Data Vector ◽  
Energy Survey

ABSTRACT Beyond ΛCDM, physics or systematic errors may cause subsets of a cosmological data set to appear inconsistent when analysed assuming ΛCDM. We present an application of internal consistency tests to measurements from the Dark Energy Survey Year 1 (DES Y1) joint probes analysis. Our analysis relies on computing the posterior predictive distribution (PPD) for these data under the assumption of ΛCDM. We find that the DES Y1 data have an acceptable goodness of fit to ΛCDM, with a probability of finding a worse fit by random chance of p = 0.046. Using numerical PPD tests, supplemented by graphical checks, we show that most of the data vector appears completely consistent with expectations, although we observe a small tension between large- and small-scale measurements. A small part (roughly 1.5 per cent) of the data vector shows an unusually large departure from expectations; excluding this part of the data has negligible impact on cosmological constraints, but does significantly improve the p-value to 0.10. The methodology developed here will be applied to test the consistency of DES Year 3 joint probes data sets.

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