scholarly journals Quantifying hydraulic roughness from field data: can dune morphology tell the whole story?

2021 ◽  
Author(s):  
Sjoukje Irene de Lange ◽  
A.J.F. (Ton) Hoitink ◽  
Suleyman Naqshband
Keyword(s):  
Field Data ◽  
Hydraulic Roughness ◽  
Dune Morphology

scholarly journals Predicted ripple dimensions in relation to the precision of in situ measurements in the southern North Sea

Ocean Science ◽  
2016 ◽  
Vol 12 (6) ◽  
pp. 1221-1235 ◽  
Author(s):  
Knut Krämer ◽  
Christian Winter
Keyword(s):  
North Sea ◽  
Field Data ◽  
Morphological Features ◽  
Sediment Properties ◽  
Hydraulic Roughness ◽  
Digital Elevation ◽  
Shelf Sea ◽  
Waves And Currents ◽  
Accuracy Of Measurement

Abstract. Ripples are common morphological features in sandy marine environments. Their shapes and dimensions are closely related to local sediment properties and forcing by waves and currents. Numerous predictors for the geometry and hydraulic roughness of ripples exist but, due to their empirical nature, they may fail to properly reflect conditions in the field. Here, measurements of tide and wave generated ripples in a shallow shelf sea are reported. Discrete and continuous methods for the extraction of ripple dimensions from digital elevation models (DEMs) are inter-compared. The range of measured ripple dimensions is quantified and compared to the results of empirical predictors. The repeatability of a measurement for inactive conditions is taken as the precision of measurements of bedform dimensions. The accuracy of measurement is assessed via comparison to predicted dimensions. Results from field data show that the precision of measurements is limited to 10 % of the absolute ripple dimensions. The application of different methods for the detection of ripple heights may result in form roughness heights differing by a factor of up to 2 between the traditional statistical estimate and a full evaluation of the spatial bathymetry.

Quantifying hydraulic roughness from field data: can bed morphology tell the whole story?

2021 ◽  
Author(s):  
Sjoukje de Lange ◽  
Suleyman Naqshband ◽  
Ton Hoitink
Keyword(s):  
Spatial Distribution ◽  
Flow Velocity ◽  
Water Surface ◽  
Field Data ◽  
Morphological Characteristics ◽  
Fundamental Parameter ◽  
Surface Slope ◽  
Hydraulic Roughness ◽  
Bed Morphology ◽  
Water Surface Slope

<p>Bedforms are thought to be a major cause of hydraulic roughness in channels. The geometry of the river bed, shaped by bars, dunes, and ripples, and the spatial and temporal distribution of these, influence the resulting roughness variations. Roughness is a fundamental parameter for understanding river flow behaviour by influencing sediment transport and water level.</p><p>Quantification of roughness is challenging since it is not directly measurable in the field. It is therefore inferred from hydrological characteristics, -including water depth, water surface slope, flow velocity, discharge-, as well as morphological characteristics, -such as bedform height-, or derived from calibration of a hydraulic model.</p><p>This study contributes to the elucidation of factors influencing hydraulic roughness, and its quantification from field data. Proper quantification of roughness and its spatiotemporal behavior will increase our knowledge in river behavior and will lead to improvement of river management strategies and operational models.</p><p>In this research, three methods will be explored, to quantify the spatial distribution of hydraulic roughness in the field. We aim to state the importance of bed morphology for hydraulic roughness and we pursue the auxiliary aim to explore the spatial distribution of bedforms and roughness in our case study area river Waal, the Netherlands.</p><p>Method 1 uses the St. Vernant equations (better known as the Chezy equations) to quantify roughness, with as input among others flow velocity, bed slope and water surface slope. This value is seen as the ‘true’  roughness of the river system. Method 2 is a traditionally often used method, where form roughness is obtained from dune characteristics such as height and length via empirical predictors. Method 3 makes use of characteristics of the bed itself, not strictly related to 2D bedform geometry, specifically the inclination of the streamwise local elevation profile, i.e. local topographic leeside angle. Doing so eliminates the necessity of defining dune characteristics, and therefore taking one, often arbitrary, step out of the procedure to quantify roughness.</p><p>The three methodologies show the same general trend and order of magnitude of roughness (C=30-70 m<sup>0.5</sup>/s, mean 42 m<sup>0.5</sup>/s) however kilometer-scale variations show contrasting patterns. Nor dune geometry neither local topographic leeside angle manage to fully explain the variations in the roughness as obtain from the st. Vernant equations. From this we conclude that bed morphology does not seem to be the only explaining factor for roughness variations. Possible explanations include the low leeside angle of dunes (mean <10°), the influence of man-made structures such as groynes and longitudinal training dams, the influence of fixed gravel layers in sharp bends, river curvature, and cross-sectional variation in river depth (bars) and flow velocity. Further steps will be made to unravel the contributing factors for spatial variation in roughness.</p>

Boussinesq Wave Model Compared with Field Data

2001 ◽  
Author(s):  
Denis Morichon ◽  
Barbara Boczar-Karakiewicz ◽  
Edward B. Thornton
Keyword(s):  
Field Data ◽  
Wave Model

Mekanisme Dan Proteksi Jaminan Nasabah Pada Gadai Informal

Liquidity ◽  
2017 ◽  
Vol 6 (2) ◽  
pp. 103-109
Author(s):  
Yuri Nanda Larasati ◽  
Jafril Khalil
Keyword(s):  
Qualitative Research ◽  
Research Methods ◽  
Financial Services ◽  
Field Data ◽  
Qualitative Research Methods ◽  
Research Field ◽  
Consumer Society ◽  
Library Research ◽  
The Cost

Regulation of the financial services authority (OJK) No. 31/POJK.05/2016 on Venture had arranged that the financial services agency on the basis of the law of pledge is in coaching and supervision OJK. Yet the existence of laws – invitation to Governing Enterprise pawn shops causing business activities conducted by the above parties are not yet regulated. The condition is feared could cause harm to the consumer society. The purpose of this research is to know the procedures, mechanisms, protection of goods and guarantee the consumer on an informal pledge financing, methods of determination of the cost of maintenance of the goods and the goods of the execution mechanism of the pledge as well as protection for the collateral items are viewed from the side of the consumer by looking at laws-invitations and Sharia. To find out whether the pledge have gotten permission from OJK. This research uses qualitative research methods with the study of library research, field data and simulations. The approach used in this study is the empirical juridical approach. Elaboration upon the results is discussed further in this article.

The box-balance model: a new tool to assess fish larval survival, applied to field data on two small pelagic fish

2020 ◽  
Vol 650 ◽  
pp. 289-308 ◽  
Author(s):  
V Raya ◽  
J Salat ◽  
A Sabatés
Keyword(s):  
Field Data ◽  
Fish Larvae ◽  
Larval Growth ◽  
Warming Trend ◽  
Mortality Rates ◽  
Larval Survival ◽  
Pelagic Fish ◽  
Balance Model ◽  
Small Pelagic Fish ◽  
Mesoscale Structures

This work develops a new method, the box-balance model (BBM), to assess the role of hydrodynamic structures in the survival of fish larvae. The BBM was applied in the northwest Mediterranean to field data, on 2 small pelagic fish species whose larvae coexist in summer: Engraulis encrasicolus, a dominant species, and Sardinella aurita, which is expanding northwards in relation to sea warming. The BBM allows one to quantify the contribution of circulation, with significant mesoscale activity, to the survival of fish larvae, clearly separating the effect of transport from biological factors. It is based on comparing the larval abundances at age found in local target areas, associated with the mesoscale structures (boxes), to those predicted by the overall mortality rate of the population in the region. The application of the BBM reveals that dispersion/retention by hydrodynamic structures favours the survival of E. encrasicolus larvae. In addition, since larval growth and mortality rates of the species are required parameters for application of the BBM, we present their estimates for S. aurita in the region for the first time. Although growth and mortality rates found for S. aurita are both higher than for E. encrasicolus, their combined effect confers a lower survival to S. aurita larvae. Thus, although the warming trend in the region would contribute to the expansion of the fast-growing species S. aurita, we can confirm that E. encrasicolus is well established, with a better adapted survival strategy.

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