Evaluation of Manning’s n Roughness Coefficient in Arid Environments by Using SAR Backscatter

The prediction of arid region flash floods (magnitude and frequency) is essential to ensure the safety of human life and infrastructures and is commonly based on hydrological models. Traditionally, catchment characteristics are extracted using point-based measurements. A considerable improvement of point-based observations is offered by remote sensing technologies, which enables the determination of continuous spatial hydrological parameters and variables, such as surface roughness, which significantly influence runoff velocity and depth. Hydrological models commonly express the surface roughness using Manning’s roughness coefficient (n) as a key variable. The objectives were thus to determine surface roughness by exploiting a new high spatial resolution spaceborne synthetic aperture radar (SAR) technology and to examine the correlation between radar backscatter and Manning’s roughness coefficient in an arid environment. A very strong correlation (R2 = 0.97) was found between the constellation of small satellites for Mediterranean basin observation (COSMO)-SkyMed SAR backscatter and surface roughness. The results of this research demonstrate the feasibility of using an X-band spaceborne sensor with high spatial resolution for the evaluation of surface roughness in flat arid environments. The innovative method proposed to evaluate Manning’s n roughness coefficient in arid environments with sparse vegetation cover using radar backscatter may lead to improvements in the performance of hydrological models.

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Manning’s N Value of Bridge-in-Backpack

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.638-640.965 ◽

2014 ◽

Vol 638-640 ◽

pp. 965-968

Author(s):

Jing Ma ◽

Ling Qiang Yang

Keyword(s):

Water Flow ◽

Roughness Coefficient ◽

N Value ◽

New Type ◽

Manning’S Roughness Coefficient ◽

Manning’S N ◽

Manning's N

Bridge-in-a-Backpack is a new type bridge. this study will investigate the interaction of flow under the bridge with the tubes and decking, and recommend Manning’s roughness coefficient for water flow under the composite backbridge system.

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The Manning’s Roughness Coefficient Calibration Method to Improve Flood Hazard Analysis in the Absence of River Bathymetric Data: Application to the Urban Historical Zamora City Centre in Spain

Applied Sciences ◽

10.3390/app11199267 ◽

2021 ◽

Vol 11 (19) ◽

pp. 9267

Author(s):

Julio Garrote ◽

Miguel González-Jiménez ◽

Carolina Guardiola-Albert ◽

Andrés Díez-Herrero

Keyword(s):

Urban Areas ◽

Flood Hazard ◽

Flood Damage ◽

City Centre ◽

Average Error ◽

Accurate Estimation ◽

Roughness Coefficient ◽

Flow Depth ◽

Manning’S N ◽

Manning's N

The accurate estimation of flood risk depends on, among other factors, a correct delineation of the floodable area and its associated hydrodynamic parameters. This characterization becomes fundamental in the flood hazard analyses that are carried out in urban areas. To achieve this objective, it is necessary to have a correct characterization of the topography, both inside the riverbed (bathymetry) and outside it. Outside the riverbed, the LiDAR data led to an important improvement, but not so inside the riverbed. To overcome these deficiencies, different models with simplified bathymetry or modified inflow hydrographs were used. Here, we present a model that is based upon the calibration of the Manning’s n value inside the riverbed. The use of abnormally low Manning’s n values made it possible to reproduce both the extent of the flooded area and the flow depth value within it (outside the riverbed) in an acceptable manner. The reduction in the average error in the flow depth value from 50–75 cm (models without bathymetry and “natural” Manning’s n values) to only about 10 cm (models without bathymetry and “calibrated” Manning’s n values), was propagated towards a reduction in the estimation of direct flood damage, which fell from 25–30% to about 5%.

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The First Comparisons of IMERG and the Downscaled Results Based on IMERG in Hydrological Utility over the Ganjiang River Basin

Water ◽

10.3390/w10101392 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1392 ◽

Cited By ~ 8

Author(s):

Ziqiang Ma ◽

Xiao Tan ◽

Yuan Yang ◽

Xi Chen ◽

Guangyuan Kan ◽

...

Keyword(s):

River Basin ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Vital Role ◽

Hydrological Models ◽

Observation Methods ◽

Satellite Retrievals ◽

Precipitation Estimates ◽

Streamflow Simulation ◽

Ganjiang River Basin

Rainfall information is a prerequisite to and plays a vital role in driving hydrological models. However, limited by the observation methods, the obtained precipitation data, at present, are still too coarse. In this study, a new downscaling method was proposed to obtain high spatial resolution (~1 km/hourly) precipitation estimates based on Integrated Multi-satellitE Retrievals for GPM (IMERG) data at hourly scale. Compared with original IMERG data, the downscaled precipitation results showed the similar spatial patterns with those of original IMERG data, but with finer spatial resolution. In addition, the downscaled precipitation estimates were further analyzed to quantify their improvements using the Coupled Routing and Excess STorage (CREST) model across Ganjiang River basin. Compared with the observed streamflow, the downscaled precipitation results showed satisfying hydrological performance, with Nash-Sutcliffe Coefficient of Efficiency (NSCE), Root Mean Square Error (RMSE), Relative Bias (BIAS), and Correlation Coefficient (CC). The improvement in terms of four statistic metrics in terms of streamflow simulation also indicated great potential of hydrological utility for the downscaled precipitation results.

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Gene expression programming to predict Manning’s n in meandering flows

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2016-0569 ◽

2018 ◽

Vol 45 (4) ◽

pp. 304-313 ◽

Cited By ~ 6

Author(s):

Arpan Pradhan ◽

Kishanjit K. Khatua

Keyword(s):

Gene Expression ◽

Field Study ◽

Discharge Capacity ◽

Gene Expression Programming ◽

Roughness Coefficient ◽

Compound Channel ◽

Factors Affecting ◽

Manning’S N ◽

Bed Material ◽

Manning's N

Accurate prediction of Manning’s roughness coefficient is essential for the computation of conveyance capacity in open channels. There are various factors affecting the roughness coefficient in a meandering compound channel and not just the bed material. The factors, geometric as well as hydraulic, are investigated and incorporated in the prediction of Manning’s n. In this study, a new and accurate technique, gene expression programming (GEP) is used to estimate Manning’s n. The estimated value of Manning’s n is used in the evaluation of the conveyance capacity of meandering compound channels. Existing methods on conveyance estimation are assessed to carry out a comparison between them and the proposed GEP model. Results show that the discharge capacity computed by the new model provides far better results than the traditional models. The developed GEP model is validated with three individual sections of a natural river, signifying that the model can be applied to field study of rivers, within the stated range of parameters.

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High spatial resolution AEM observations of yttrium segregation in chromia scales grown on Co-45%Cr

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144103 ◽

1986 ◽

Vol 44 ◽

pp. 518-519

Author(s):

K. Przybylski ◽

A. J. Garratt-Reed ◽

G. J. Yurek

Keyword(s):

Spatial Resolution ◽

Outer Surface ◽

Maximum Concentration ◽

High Spatial Resolution ◽

Reactive Elements ◽

Chromia Scales

The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.

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Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010016323x ◽

1996 ◽

Vol 54 ◽

pp. 154-155

Author(s):

E. G. Rightor

Keyword(s):

Excited State ◽

Polymer Blends ◽

Gas Phase ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Electronic States ◽

Core Electron ◽

Bulk Solids ◽

Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

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