scholarly journals Accurate Open Channel Flowrate Estimation Using 2D RANS Modelization and ADCP Measurements

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1772
Author(s):  
Juan Alfonso Figuérez ◽  
Javier González ◽  
Álvaro Galán
Keyword(s):  
Velocity Distribution ◽  
Cross Sections ◽  
Velocity Model ◽  
Streamwise Velocity ◽  
Hydraulic Model ◽  
Measurement Information ◽  
Area Method ◽  
Hydraulic Behaviour ◽  
Adcp Measurements ◽  
Discrete Integration

Boat-mounted Acoustic Doppler Current Profilers (ADCP) are commonly used to measure the streamwise velocity distribution and discharge in rivers and open channels. Generally, the method used to integrate the measurements is the velocity-area method, which consists of a discrete integration of flow velocity over the whole cross-section. The discrete integration is accomplished independently in the vertical and transversal direction without assessing the hydraulic coherence between both dimensions. To address these limitations, a new alternative method for estimating the discharge and its associated uncertainty is here proposed. The new approach uses a validated 2D RANS hydraulic model to numerically compute the streamwise velocity distribution. The hydraulic model is fitted using state estimation (SE) techniques to accurately reproduce the measurement field and hydraulic behaviour of the free-surface stream. The performance of the hydraulic model has been validated with measurements on two different trapezoidal cross-sections in a real channel, even with asymmetric velocity distribution. The proposed method allows extrapolation of measurement information to other points where there are no measurements with a solid and consistent hydraulic basis. The 2D-hydraulic velocity model (2D-HVM) approach discharge values have been proven more accurate than the ones obtained using velocity-area method, thank to the enhanced use of the measurements in addition to the hydraulic behaviour represented by the 2D RANS model.

Hydraulic modelling of extreme flood event of semi-arid river basin

2021 ◽  
Author(s):  
Mohamedmaroof Shaikh ◽  
Sanjaykumar Yadav ◽  
Vivek Manekar
Keyword(s):  
Cross Sections ◽  
Management Strategy ◽  
Retaining Wall ◽  
Hydraulic Model ◽  
Flood Event ◽  
Railway Bridge ◽  
Hydraulic Modelling ◽  
One Dimensional ◽  
Extreme Flood ◽  
High Flood

<p>Floods are among the severe weather disasters that cause catastrophic damage to surroundings and adversely impact populations. This study aims to create a one-dimensional (1D) hydraulic model using HEC-RAS for the Rel River in Banaskantha, Gujarat, India. The model has been developed for the extreme flood event of July 2017. A total of hundred cross-sections have been used as geometric data. The peak discharge of 3355 m<sup>3</sup>/s and the river slope has been applied as upstream and downstream boundary conditions. The model has been calibrated and validated using observed water depth at Railway bridge and Highway bridge. Critical cross-sections have been identified using the 1D hydraulic model. Eight out of the hundred cross-sections were safe for a flood discharge of 3355 m<sup>3</sup>/s. The villages at high flood risk are identified for this discharge. To mitigating floods, the construction of a retaining wall or levees is recommended to protect these villages. This study can help a disaster management strategy for the cities and town in the River’s vicinity.</p>

Two robust imaging methodologies for challenging environments: Wave-equation dispersion inversion of surface waves and guided waves and supervirtual interferometry + tomography for far-offset refractions

2018 ◽  
Vol 6 (4) ◽  
pp. SM27-SM37 ◽  
Author(s):  
Jing Li ◽  
Kai Lu ◽  
Sherif Hanafy ◽  
Gerard Schuster
Keyword(s):  
Wave Equation ◽  
Velocity Distribution ◽  
Surface Waves ◽  
Guided Waves ◽  
Velocity Model ◽  
Dispersion Curves ◽  
P Wave ◽  
Head Wave ◽  
Near Surface ◽  
Velocity Models

Two robust imaging technologies are reviewed that provide subsurface geologic information in challenging environments. The first one is wave-equation dispersion (WD) inversion of surface waves and guided waves (GW) for the shear-velocity (S-wave) and compressional-velocity (P-wave) models, respectively. The other method is traveltime inversion for the velocity model, in which supervirtual refraction interferometry (SVI) is used to enhance the signal-to-noise ratio of far-offset refractions. We have determined the benefits and liabilities of both methods with synthetic seismograms and field data. The benefits of WD are that (1) there is no layered-medium assumption, as there is in conventional inversion of dispersion curves. This means that 2D or 3D velocity models can be accurately estimated from data recorded by seismic surveys over rugged topography, and (2) WD mostly avoids getting stuck in local minima. The liability is that WD for surface waves is almost as expensive as full-waveform inversion (FWI) and, for Rayleigh waves, only recovers the S-velocity distribution to a depth no deeper than approximately 1/2 to 1/3 wavelength of the lowest-frequency surface wave. The limitation for GW is that, for now, it can estimate the P-velocity model by inverting the dispersion curves from GW propagating in near-surface low-velocity zones. Also, WD often requires user intervention to pick reliable dispersion curves. For SVI, the offset of usable refractions can be more than doubled, so that traveltime tomography can be used to estimate a much deeper model of the P-velocity distribution. This can provide a more effective starting velocity model for FWI. The liability is that SVI assumes head-wave first arrivals, not those from strong diving waves.

Well-Log-Based Velocity and Density Models for the Montney Unconventional Resource Play in Northeast British Columbia, Canada, Applicable to Induced Seismicity Monitoring and Research

2020 ◽  
Author(s):  
Alireza Babaie Mahani ◽  
Dmytro Malytskyy ◽  
Ryan Visser ◽  
Mark Hayes ◽  
Michelle Gaucher ◽  
...  
Keyword(s):  
British Columbia ◽  
Hydraulic Fracturing ◽  
Cross Sections ◽  
Induced Seismicity ◽  
Focal Depth ◽  
Depth Resolution ◽  
Velocity Model ◽  
The North ◽  
Seismicity Monitoring ◽  
Unconventional Resource

Abstract We present detailed velocity and density models for the Montney unconventional resource play in northeast British Columbia, Canada. The new models are specifically essential for robust hypocenter determination in the areas undergoing multistage hydraulic-fracturing operations and for detailed analysis of induced seismicity processes in the region. For the upper 4 km of the sedimentary structure, we review hundreds of well logs and select sonic and density logs from 19 locations to build the representative models. For depths below 4 km, we extend our models using data from the southern Alberta refraction experiment (Clowes et al., 2002). We provide one set of models for the entire Montney play along with two separated sets for the southern and northern areas. Specifically, the models for the southern and northern Montney play are based on logs located in and around the Kiskatinaw Seismic Monitoring and Mitigation Area and the North Peace Ground Motion Monitoring area, respectively. To demonstrate the usefulness of our detailed velocity model, we compare the hypocenter location of earthquakes that occurred within the Montney play as determined with our model and the simple two-layered model (CN01) routinely used by Natural Resources Canada. Locations obtained by our velocity model cluster more tightly with the majority of events having root mean square residual of <0.2  s compared with that of <0.4  s when the CN01 model is used. Cross sections of seismicity versus depth across the area also show significant improvements in the determination of focal depths. Our model results in a reasonable median focal depth of ∼2  km for events in this area, which is consistent with the completion depths of hydraulic-fracturing operations. In comparison, most solutions determined with the CN01 model have fixed focal depths (0 km) due to the lack of depth resolution.

Reconstructing a hydraulic model for historic flood levels in the city of Bath, United Kingdom

2020 ◽  
Author(s):  
Ioanna Stamataki ◽  
Thomas Kjeldsen
Keyword(s):  
United Kingdom ◽  
Cross Sections ◽  
Flood Risk ◽  
Hydraulic Model ◽  
Water Levels ◽  
Roughness Coefficient ◽  
Documentary Evidence ◽  
Flood Events ◽  
Historical Evidence ◽  
The City

<p>Assessing the risk of future flood events and the implications for flood risk in cities is an economically and socially costly problem. In this research, we assess the utility of documentary evidence of past flood events for contemporary flood risk assessments to reduce the uncertainty in flood frequency estimation due to the interpolation from short annual maximum series (AMS) records.</p><p>The historical city of Bath, United Kingdom, developed in close relation to the River Avon, and evidence of flooding in the city of Bath can be traced back to Roman occupation. For this research a particularly rich record of historical evidence was chosen occurring from the 19<sup>th</sup> century onwards with flood marks on buildings through-out the city as well as documentary evidence in contemporary newspapers and technical reports. The earliest flood mark found in the city of Bath dates to 1823 with 15 more extreme floods after that marked as well. The extensive flooding in 1947 initiated work on what eventually became the present-day Bath flood protection scheme (BFS) which was implemented after the 1960 catalyst flood event.</p><p>Using an existing one-dimensional hydraulic model representing the current hydraulic system of the River Avon in Bath, a historical survey of how the river and its management has changed over time was conducted. The model was developed using historical evidence (e.g. maps, flood marks, photographs, newspaper articles etc), surveyed river cross sections, recorded and design hydrographs from National datasets.</p><p>The 1960 flood is reconstructed numerically using all available data, from flood marks to old surveyed river cross sections.  The resulting hydraulic model is used to investigate the effect of the Bath Flood Defence Scheme. Sensitivity studies with different values for the roughness coefficient are also presented in order to assess the uncertainty on water levels during extreme events. Finally, the numerically reconstructed historical peak flood discharge is compared with the results obtained using a simple Manning equation approach to assess the two methods. This paper demonstrates how hydraulic modelling can be applied to historical data and offers considerable potential to further investigations in the improvement of design flood flows.</p>

scholarly journals The streamwise velocity distribution in a two-stage channel with ice cover

2021 ◽  
Author(s):  
Yu Bai ◽  
Guojin Sun
Keyword(s):  
Experimental Data ◽  
Point Source ◽  
Velocity Distribution ◽  
Research Study ◽  
Streamwise Velocity ◽  
Ice Cover ◽  
Drainage Ditch ◽  
Point Source Pollution ◽  
Two Stage ◽  
Non Point Source Pollution

Abstract The problem of agricultural non-point source pollution has become increasingly serious. How to determine the ecological drainage ditch system is one of the effective methods to solve the agricultural non-point source pollution. This research study focuses on the velocity distribution in a two-stage section ecological channel with ice cover. The results show that the two-stage section channel with ice cover can effectively reduce the flow velocity in the channel and increase the retention time of water in the channel. By comparing with the experimental data, the accuracy of the analytical solution is high, which provides a theoretical reference for the transport of sediment and pollutions in a two-stage section channel with ice cover in the future.

scholarly journals Optimizing the Selection of Cross Section Using Information Theory: a Case in the Magdalena River, Colombia

10.29007/k855 ◽  
2018 ◽  
Author(s):  
Sara Alonso ◽  
Elena Ridolfi ◽  
Chiara Biscarini ◽  
Leonardo Alfonso
Keyword(s):  
Information Theory ◽  
Cross Sections ◽  
Model Simulation ◽  
Model Performance ◽  
Optimization Method ◽  
Joint Entropy ◽  
Cross Sectional ◽  
Total Correlation ◽  
Hydraulic Behaviour ◽  
Magdalena River

Accurate flood propagation and inundation models are crucial in flood risk assessments. For fast flowing rivers such as the Magdalena River (Colombia) with high vulnerability and exposure rates is even more essential. Indeed, floods in Magdalena River account for 90% of the damages and 70% of the causalities in Colombia. River cross-sectional information (i.e. their number and spacing) must be optimally selected to properly capture river’s hydraulic behaviour. Optimization is a powerful tool for doing such selection often necessary to increase the efficiency of field works and decrease model simulation time. A methodology based on the entropy concept provides interesting results in agreement with those proposed in literature. The optimization method proposes the use of two concepts belonging to information theory: the joint entropy and total correlation. Total correlation quantifies the redundancy of cross-sections; joint entropy provides their information content. This approach is applied to a reach of the Magdalena River. This study analyses the interrelation between the location of the optimal set of cross-sections and the hydraulic behaviour of the Middle-Magdalena River. Further work considers the evaluation of model performance with the optimized cross-sections, where no negative impacts on the reliability of flood profiles with respect to the original model are expected.

scholarly journals Tomographic Experiments for Defining the 3D Velocity Model of an Unstable Rock Slope to Support Microseismic Event Interpretation

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 327
Author(s):  
Zhiyong Zhang ◽  
Diego Arosio ◽  
Azadeh Hojat ◽  
Luigi Zanzi
Keyword(s):  
Rock Mass ◽  
Velocity Distribution ◽  
Velocity Model ◽  
Microseismic Monitoring ◽  
Time Inversion ◽  
Basic Step ◽  
Rock Face ◽  
3D Velocity Model ◽  
Microseismic Events ◽  
The Stability

To monitor the stability of a mountain slope in northern Italy, microseismic monitoring technique has been used since 2013. Locating microseismic events is a basic step of this technique. We performed a seismic tomographic survey on the mountain surface above the rock face to obtain a reliable velocity distribution in the rock mass for the localization procedure. Seismic travel-time inversion showed high heterogeneity of the rock mass with strong contrast in velocity distribution. Low velocities were found at shallow depth on the top of the rock cliff and intermediate velocities were observed in the most critical area of the rock face corresponding to a partially detached pillar. Using the 3D velocity model obtained from inversion, localization tests were performed based on the Equal Differential Time (EDT) localization method. The results showed hypocenter misfits to be around 15 m for the five geophones of the microseismic network and the error was significantly decreased compared to the results produced by a constant velocity model. Although the localization errors are relatively large, the accuracy is sufficient to distinguish microseismic events occurring in the most critical zone of the monitored rock mass from microseismic events generated far away. Thus, the 3D velocity model will be used in future studies to improve the classification of the recorded events.

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