Electromagnetic Current Meters Research Articles

Effect of hydrological variability on suspended sediment load at a river junction: a case study

Abstract Confluences act as crucial intersection in a fluvial system as they regulate the flow, sediment, and geomorphological stability. Two of the natural occurrences that have an effect on hydro-morphological processes that characterize the channel are sediment movement and stream discharge. However, assessments of suspended sediment distribution patterns across channel confluences and functions of tributaries on sediment transfer in downstream streams are still inadequately explored. To fulfil this, a year-long field investigation was conducted around river confluence at various time scales during the hydrological season. The bathymetry of the confluence was performed using digital echo-sounding equipment, electro-magnetic current meter, and differential global positioning equipment. This study uses in situ measurement and empirical techniques to quantify the spatiotemporal distribution of suspended sediment particles. Furthermore, Yang's formula was used to analyze the sediment concentration, and several statistical standards were employed to establish a differentiation between predicted and observed data. The results illustrated that a good agreement has been achieved among the calculated and measured statistics based on the correlation coefficient value. According to the findings, 8% fewer errors in the quantification of suspended sediment were induced in the tributary than in the main river because of the very low flow of the tributary. The present ramifications can help increase our database and understanding of the dynamics of major river confluences.

Coupled dynamics of the moving Antarctic krill trawl structure and its hydrodynamics behavior using various catch sizes and door spreads based on wavelet-based and Fourier analysis

Antarctic krill is a key element of the complex ecology of the Antarctic Ocean and a target species for commercial fisheries for aquaculture supply, krill oil production, and as a major food source for various natural predators. Therefore, understanding the interaction between the fluid structures of the Antarctic krill trawl structure is the key factor in solving problems such as selectivity, energy efficiency, catchability, and ecological sustainability in this fishery. Thus, this study experimentally investigated the influence of catch sizes, door spread, and inflow velocities on the bridle tension, trawl motions, trawl deformation, and flow field inside and around a scaled trawl model in flume tank based on the electromagnetic current velocity meter measurements. Fourier analysis using power spectrum density and the continuous wavelet transform is used to analyze the time-frequency contents of the instantaneous flow velocities, bridle tension, and trawl motions; and in the interaction between the unstable turbulent flows and the fluttering trawl motions, wavelet coherency analysis was employed to detect coherent structures. Results indicated that the bridle tension and trawl motions increased as the catch size, door spread, and inflow velocity increased. Owing to the significant trawl deformation, a complex fluid–structure interaction occurred and a strong positive correlation between the bridle tension and trawl motions was obtained. Furthermore, a significant decrease in the flow field occurred inside and outside different parts of the trawl. Fourier and wavelet analysis results showed that the trawl motions and bridle tension are mainly of a low-frequency activity and of another component related to the unsteady turbulent flow street, and decreased with the increasing catch size and door spread. A complex fluid–structure interaction is then demonstrated where the hydrodynamics of the moving Antarctic krill trawl structure are an intricate interplay between trawl fluttering motions and unsteady turbulent flow influenced by catch size and door spread. The knowledge of such trawl hydrodynamic behavior is of great importance to understand and design the optimal structure of trawl nets to maintain the sustainability of the Antarctic krill fishery.

Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

The interaction between fluid and the midwater trawl with stocked catches is extremely complex, but essential to improve the understanding of the drag force acting on the trawl, the behavior of the fishing structure during a trawling process, and to predict its selectivity process. The present study assesses the turbulent characteristics inside and around the midwater trawls with catch and without catch linked to its fluttering motion. The analysis is based on three-dimensional electromagnetic current velocity meter measurements performed in the multiple points inside and outside different parts of a 1/35 scaled midwater trawl model with the aim of access the main turbulent flow structure inside and around the gear. Time-averaged normalized flow velocity fields and turbulent flow parameters were analyzed from the measured flow data. Furthermore, Fourier analysis was conducted by watching the time–frequency Power spectrum content of instantaneous flow velocities fields, the fluttering trawl motions, turbulent kinetic energy, and momentum flux. Based on successive analyzes of mean flow characteristics and turbulent flow parameters, it has been demonstrated that the presence of catch inside the trawl net impacts the evolution of unsteady turbulent flow by creating large trawl fluttering motions that strongly affect the flow passage. The results showed that the time-averaged normalized streamwise and transverse flow velocities inside and around the trawl net with catch were 12.41% lower compared with that obtained inside and around the trawl without catch. The turbulent length scale and turbulent Reynolds number obtained in the different part of the trawl net with catch were about 33.05% greater than those obtained on the trawl net without catch, confirming that the unsteady turbulent flow developing inside and around the midwater trawl is influence by the catch and liner. It is observed that the motions of both the trawl without catch and the trawl with catch are mainly of a low-frequency activity and another component related to unsteady turbulent flow street. A complex fluid–structure interaction is then demonstrated where the fluttering motions of the trawl net affect the fluid flow inside and around trawl net, the fluid force, turbulent pattern, and simultaneously, the periodic unsteady turbulent flow influence the trawl motions.

Spatial patterns of transport‐effective flow at three small confluences: Relation to channel morphology

AbstractThe spatial patterns of transport‐effective flows at confluences and the relation of these patterns to channel morphology remain poorly understood. This field study uses acoustic Doppler current profiler measurements to explore the spatial structure of different transport‐effective flows at three small stream confluences where measurements of flow structure have been obtained previously using electromagnetic current meters or acoustic Doppler velocimeters for events incapable of mobilizing bed material or for transport‐effective events with much smaller discharges. Results show that flow accelerates from upstream to downstream for all six measured flows and that in each case a distinct region of velocity deficit exists within the confluence. Accelerating flow within this velocity‐deficit region eventually transforms into the high‐velocity core of flow downstream of the confluence. Patterns of secondary flow are indicative of helical motion, with some helical cells exhibiting senses of rotation inconsistent with patterns of streamline curvature defined by patterns of depth‐averaged velocity vectors—a type of fluid motion that contrasts with flow structure documented at lower stages. Channel form, especially bed morphology, generally reflects acceleration of flow at the confluences; all three sites exhibit zones of scour. Despite mobility of bed material during measured flows, channel morphology does not change substantially at any of the sites, but systematic change in channel form for two different transport‐effective events with different momentum flux ratios is observed at one of the three confluences. At this confluence, the type of change documented during the two events is consistent with previous work on changes in morphology before and after events with different momentum flux ratios. The results of this study improve understanding of the connections between flow structure and channel form at small lowland stream confluences.

Development of Electromagnetic Current Meter for Marine Environment

Ocean current is one of the most important parameters in ocean observation, and ocean current measurement based on electromagnetic induction is becoming more and more important because of its advantages such as simple structure and high measurement accuracy. However, it is difficult to detect weak current signals in a complex marine environment. In this paper, an electromagnetic induction current measurement scheme based on lock-in amplification technology is proposed. Key technologies such as the evaluation of induced current intensity, overall design, circuit design, and orientation design of the current meter were studied. The prototype of the electromagnetic current meter was developed and tested in the laboratory and at sea. The repeatability of current velocity and current direction was higher than 1.5 cm/s and 1.5°, respectively. A comparison test between the electromagnetic current meter prototype and Nortek ADCP (Acoustic Doppler Current Profiler) installed on a buoy at sea was carried out, and the correlation coefficients of the current velocity and current direction datum were 0.90 and 0.96, respectively. Through continuous on-site and fault-free operations at sea, the experimental data show that the electromagnetic current meter has good adaptability at sea, which provides feasible technical and equipment support for ocean current observation.

Comparison of platform and sea-bed mounted flow measurement instrumentation for SME PLAT-I

Tidal resource assessment for the characterisation of turbine performance or Annual Energy Prediction currently uses the method of bins as recommended by international standards. An alternative method is proposed in this paper and applied to the Sustainable Marine Energy PLAT-I deployment in Connel Sound, Scotland. This method may be suitable for tidal turbines which operate from the surface. Three instrumentation types are used in this work, a bed-mounted Acoustic Doppler Profiler (ADP), and platform-mounted Acoustic Doppler Velocimeter (ADV) and Electromagnetic Current Meter (ECM). By comparing the resource characteristics from these three sources, a comparison of their velocity magnitudes and turbulence characteristics is made, demonstrating the difference between methodologies. It was found that the ADP evaluated using the method of bins produced a more conservative velocity distribution, in comparison to the ADV and ECM. Consequently, a representative AEP showed a difference of 3.8kWh (50% of ADP total) for the month of data collected. When comparing the Turbulence Intensity between devices, the ADP and ECM had similar metrics whilst the ADV had up to 14% higher values. The significance of these differences requires further work comparing them to the SME PLAT-I turbines power output to ascertain which best represents the onset flow experienced by the turbine and if there is a correlation between power performance and turbulence intensity.

Ship wake forcing and performance of a living shoreline segment on an estuarine shoreline

Investigation of the effectiveness of Natural and Nature-Based Features (NNBF) for protecting shorelines from ship wake is increasingly important with continued development along the coast, especially when combined with sea level rise. Studies that investigate the wave energy dissipation capacity of different techniques and account for variation in context will lead to improvements and innovation in designed NNBF. Few studies have examined the performance of NNBF in protecting shorelines from ship wake. In this study of a low-sloping estuarine shoreline adjacent to a major shipping route, a natural design using coir logs and wooden staking was implemented in a T-head groin configuration. Pressure transducers and electromagnetic current meters were deployed over ∼1.5 months to investigate the energy dissipation and velocity attenuation capabilities of the installation. Results indicate that ship wakes account for 25%–50% of the total daily energy impacting the shoreline at the study site. Peak background velocities are typically over 50% smaller than the largest ship wake velocities. Field data and results of the fully nonlinear Boussinesq model, FUNWAVE-TVD, indicate that the installation is capable of decreasing energy impacting the shoreline by 10%–80% and is effective over the lower 50% of the tidal range and when submerged up to twice its height. Elevation surveys of the site indicate accrual of sediment within the installation, suggesting wave diffraction patterns promoting further accretion at the site over time. Observations indicate that coir logs may be effective in reducing wave energy from ship wakes but may fail under storm conditions in a moderate fetch confined channel. Findings from this study illustrate the opportunities and challenges nature-based solutions face in addressing ship wakes, and their ability to protect shorelines under high energy stressors.

Unsteady turbulent flow developing inside and around different parts of fluttering trawl net in flume tank

Fluttering motions of a trawl are affected by its geometrical shape, natural underwater flows, and unsteady turbulent flow inside and around it. Thus, knowledge of the interaction between fluttering motions and the turbulent flow developing inside and around the different parts of the trawl is essential for understanding the hydrodynamic performance and selectivity of fishing gear. This paper assesses the coupled dynamics of the fluttering motions of different parts of a trawl and their hydrodynamics behavior. The analysis is based on three-dimensional electromagnetic current velocity meter measurements carried out inside and around different parts of a 1/18 scaled bottom trawl model. Instantaneous flow velocity fields and turbulent flow parameters were analyzed from obtained flow data. Moreover, fast Fourier transform and wavelet transform analysis were conducted to analyze the time–frequency contents of instantaneous flow velocity fields and fluctuating parts. The motions of different parts of the trawl net were oscillatory quasi-periodic and related to low frequency activity. The mean velocity ratios inside and around trawl wing, square, trawl body, and codend were 0.92, 0.89, 0.86, and 0.84, respectively. These results demonstrate the existence of unsteady turbulent flow inside and around different parts of the trawl. This unsteady turbulent flow corresponds to turbulent boundary layer flow, turbulent flow because of trawl wake, and vortex shedding. The dominant frequencies of these unsteady turbulent flows showed low frequency activities and wavelet energy was transferred from small-scale to large-scale motions under unsteady shear turbulence. In addition, knowledge of unsteady turbulent flow is greatly important for better understanding the hydrodynamic forces acting on a trawl and its geometrical shape as well as for implementing various selective devices and mesh shapes to reduce juvenile by-catch.

Identifying the turbulent flow developing inside and around the bottom trawl by Electromagnetic Current Velocity Meter approach in the flume tank

Identifying the turbulent flow developing inside and around the bottom trawl by Electromagnetic Current Velocity Meter approach in the flume tank

The role of alongshore flows on inner surf and swash zone hydrodynamics on a dissipative beach

Cross-shore and alongshore velocities were measured over five high tide cycles in the swash and inner surf zones of a dissipative beach (significant wave height between 0.5 and 1.65 m; water levels between 0 and 0.87 m) using acoustic and electromagnetic current meters. Measurements are used to determine the importance of alongshore motions relative to cross-shore motions for bed shear stress; a parameter required for many sediment transport formulations. Velocities and water depths are infragravity dominated with running average (5 min) cross-shore and alongshore velocities being of similar magnitude near 0.25 m/s. Significant coherence squared between cross-shore velocity and water depth is found in an infragravity frequency range (0.0078 Hz–0.024 Hz). A narrower infragravity frequency range (0.012 Hz–0.022 Hz) of significant coherence squared is found between alongshore velocity and water depth. Near bed velocity profiles at high spatial resolution indicate the mean profile of cross-shore or alongshore velocity for different relative cross-shore positions are nearly depth uniform, suggesting, on average, a well-mixed water column. Time-averaged onshore-directed depth-averaged velocities are nearly constant as a function of mean water depth, whereas time-averaged offshore-directed depth-averaged velocity magnitudes decrease with an increase in mean depth. In contrast, mean alongshore depth-averaged velocity magnitudes increase with depth regardless of the corresponding cross-shore motion and were always southerly-directed. These variations result from changes in breaking wave forcing location (i.e. relative cross-shore position). Near instantaneous velocity profile data are used to estimate friction coefficients and the bed shear stress through the Law of the Wall assumption. Mean friction coefficients for alongshore flows are similar to those obtained for cross-shore flows and values of ~0.02 are appropriate for all phases of flow. Alongshore bed shear stresses are the dominant bed shear stress component for over 27% of the samples implying an enhancement of total bed shear stress through incorporation of alongshore motions. Neglecting these alongshore processes (even if alongshore uniform) in cross-shore sediment transport models will lead to errors in predicted sediment transport rates.

Post-Hurricane Michael damage assessment using ADCIRC storm surge hindcast, image classification, and LiDAR

Wave forcing from hurricanes, nor’easters, and energetic storms can cause erosion of the berm and beach face resulting in increased vulnerability of dunes and coastal infrastructure. LIDAR or other surveying techniques have quantified post-event morphology, but there is a lack of in situ hydrodynamic and morphodynamic measurements during extreme storm events. Two field studies were conducted in March 2018 and April 2019 at Bethany Beach, Delaware, where in situ hydrodynamic and morphodynamic measurements were made during a nor’easter (Nor’easter Riley) and an energetic storm (Easter Eve Storm). An array of sensors to measure water velocity, water depth, water elevation and bed elevation were mounted to scaffold pipes and deployed in a single cross-shore transect. Water velocity was measured using an electro-magnetic current meter while water and bed elevations were measured using an acoustic distance meter along with an algorithm to differentiate between the water and bed during swash processes. GPS profiles of the beach face were measured during every day-time low tide throughout the storm events. Both accretion and erosion were measured at different cross-shore positions and at different times during the storm events. Morphodynamic change along the back-beach was found to be related to berm erosion, suggesting an important morphologic feedback mechanism. Accumulated wave energy and wave energy flux per unit area between Nor’easter Riley and a recent mid-Atlantic hurricane (Hurricane Dorian) were calculated and compared. Coastal Observations: JALBTCX/NCMP emergency-response airborne Lidar coastal mapping & quick response data products for 2016/2017/2018 hurricane impact assessments

In situ hydrodynamic and morphodynamic measurements during extreme storm events

Wave forcing from hurricanes, nor’easters, and energetic storms can cause erosion of the berm and beach face resulting in increased vulnerability of dunes and coastal infrastructure. LIDAR or other surveying techniques have quantified post-event morphology, but there is a lack of in situ hydrodynamic and morphodynamic measurements during extreme storm events. Two field studies were conducted in March 2018 and April 2019 at Bethany Beach, Delaware, where in situ hydrodynamic and morphodynamic measurements were made during a nor’easter (Nor’easter Riley) and an energetic storm (Easter Eve Storm). An array of sensors to measure water velocity, water depth, water elevation and bed elevation were mounted to scaffold pipes and deployed in a single cross-shore transect. Water velocity was measured using an electro-magnetic current meter while water and bed elevations were measured using an acoustic distance meter along with an algorithm to differentiate between the water and bed during swash processes. GPS profiles of the beach face were measured during every day-time low tide throughout the storm events. Both accretion and erosion were measured at different cross-shore positions and at different times during the storm events. Morphodynamic change along the back-beach was found to be related to berm erosion, suggesting an important morphologic feedback mechanism. Accumulated wave energy and wave energy flux per unit area between Nor’easter Riley and a recent mid-Atlantic hurricane (Hurricane Dorian) were calculated and compared.

A Dynamic Flight Model for Slocum Gliders and Implications for Turbulence Microstructure Measurements

Abstract The turbulent dissipation rate ε is a key parameter to many oceanographic processes. Recently, gliders have been increasingly used as a carrier for microstructure sensors. Compared to conventional ship-based methods, glider-based microstructure observations allow for long-duration measurements under adverse weather conditions and at lower costs. The incident water velocity U is an input parameter for the calculation of the dissipation rate. Since U cannot be measured using the standard glider sensor setup, the parameter is normally computed from a steady-state glider flight model. As ε scales with U2 or U4, depending on whether it is computed from temperature or shear microstructure, respectively, flight model errors can introduce a significant bias. This study is the first to use measurements of in situ glider flight, obtained with a profiling Doppler velocity log and an electromagnetic current meter, to test and calibrate a flight model, extended to include inertial terms. Compared to a previously suggested flight model, the calibrated model removes a bias of approximately 1 cm s−1 in the incident water velocity, which translates to roughly a factor of 1.2 in estimates of the dissipation rate. The results further indicate that 90% of the estimates of the dissipation rate from the calibrated model are within a factor of 1.1 and 1.2 for measurements derived from microstructure temperature sensors and shear probes, respectively. We further outline the range of applicability of the flight model.

Oceanographic conditions and sediment dynamic of the Barrang Caddi Island (Spermonde Archipelago, Indonesia)

Small islands are vulnerable to long-term natural disasters like coastal erosion due to their size and topography. Barrang Caddi is one the small island in the Spermonde Archipelago (South Sulawesi) that encountered serious coastal erosion. Several attempts have been done by the relevant parties like by building a wave breaker to prevent erosion. But in fact some parts of the island are still eroded. A comprehensive oceanographic study of the wave climate and coastal processes at work to delineate the factors responsible for shoreline chance and to identify the location that need protection is needed. In this study, physical oceanographic data including waves, currents, tide, bathymetry, sediment characteristics and sediment transport were collected in the Barrang Caddi Island to analyze the factors responsible for shoreline chance (erosion) in the island. Results of the study showed that tide in the study site is mixed tide, predominantly semidiurnal with tidal range of 118 cm. Current measurements using a electromagnetic current meter revealed that current velocities at the study site were relatively low and vary spatially and temporally with magnitude of 0.02 – 0.58 m/s. Under normal conditions (no storms) the significant wave height (H 1/3) varied from 0.04 to 0.20 m. The wave height decreases from the fore reef to the reef flat due to the presence of coral reefs that reduce wave energy (wave height). Sediments were dominated by biogenic sand with grain diameter of 0.38 – 1.04 mm. Island erosion analysis showed that wave action was a main factor that responsible for shoreline chance (erosion) at the island. Current velocity alone with average of 0.19 m/s was not strong enough to move (erode) sediments at the island.

港内の河口域近辺に発生する流れについての海洋環境調査

The waters facing the Marine Training and Research Center (MTRC) at the National Institute of Technology (NIT), Toyama College consist of a mixture of inflows from the Shinbori River, a timber pond and the open sea. In this study, we examine a particular current that is influenced by the combination of inflows and open seawater occurred in summer. This slow current, which flows westward at the speed of approximately 0.1-0.3 m/s, influences handling of small boats and the college training ship Wakashio-maru (231 GT) that operate from the MTRC pier. Accordingly, the authors conducted Conductivity, Temperature and Depth profiler (CTD), Electromagnetic current meter, and Acoustic Doppler Current Profiler (ACDP) observations of the marine environment of the flow in order to gain an understanding of the inflow waters such as their vertical formulations, seasonal variations, water structure, temperature, and salinity. The results of those observations revealed that the waters consisted of three layers, with the upper layer most influenced by the Shinbori River and the lower layer most influenced by the open sea. The middle layer was a mixture of both the upper and lower layers. It was also found that the borders of layers changed according to seasons, and that the flow was influenced by the tidal current at lower layer, the river water at upper layer and the topography.

Validation of large-scale particle image velocimetry to acquire free-surface flow fields in vegetated rivers

The reliability of large-scale particle image velocimetry (LSPIV) methodology to measure a 2D surface velocity field in a vegetated lowland stream is evaluated. To this end, measurements of the free-surface flow field obtained with LSPIV are compared with measurements with an electromagnetic current meter (ECM) close to the surface at four different locations. The measurements were performed monthly, allowing the evaluation of the LSPIV measurements in relation to different vegetated conditions. The difference observed between the mean velocities measured with ECM and LSPIV remains low in winter, whereas an increase is observed in summer. Inappropriate particle seeding density and unsteadiness of the flow are the main sources of LSPIV reliability reduction. Nonetheless, the seasonal average frequency of reliable LSPIV measurements is 97%, 95% and 78% in winter, spring and summer, respectively. The results illustrate that LSPIV is an inexpensive methodology, which provides high-resolution and reliable data to study the flow-field distribution in vegetated rivers, provided some considerations are taken into account to deal with the added complexity of the vegetation presence and the field conditions.

현장유출영상을 활용한 표면영상유속계(SIV)의 상관계수 분석

Abstract This study is daytime and nighttime runoff image data caused by heavy rain on May 27, 2013 at Oedo Water Treatment Plant of Oedo-Stream, Jeju to compute runoff by applying Surface image velocimeter (SIV) and analyzing correlation according to current. At the same time, current was comparatively analyzed using ADCP observation data and fixed electromagnetic surface current meter (Kalesto) observed at the runoff site.As a result of comparison on resolutions of daytime and nighttime runoff images collected, correlation coefficient correspondingto the range of 0.6~0.7 was 6.8% higher for nighttime runoff image compared to daytime runoff image. On the contrary, correlation coefficient corresponding to the range of 0.9~1.0 was 17% lower. This result implies that nighttime runoff image has lower image quality than daytime runoff image. In the process of computing current using SIV, a rational filtering process for correlation coefficient is needed according to images obtained. Key words

Amplification of coastal-trapped waves resonantly generated by wind around Sado Island, Japan

Current observations were made from 4 July 2009 to 6 March 2011 with an acoustic Doppler current profiler mounted on the seafloor near the northern tip of Sado Island, Japan, and an electromagnetic current meter off the western coast of the island to investigate wind-induced coastal-trapped waves (CTW). Oscillating alongshore flows with a period of about 2 days occurred intermittently in association with atmospheric disturbances throughout the observation period. The period of the current fluctuation changed from 48 to 60 h in both summer and winter, and the fluctuations were coherent with northward wind velocity fluctuations with a period of about 2 days around the island, even though northward wind fluctuations with periods of about 3, 4, and 6 days were predominant. Thus, the 2-day-period current fluctuations were selectively enhanced by the wind. Because the wavelength of internal Kelvin waves with a 2-day period was comparable to the distance around Sado Island (210 km), we inferred that the wind-induced CTWs around the island were resonant with the 2-day-period northward wind fluctuations. This inference was supported by the results of a numerical experiment performed with a two-layer model using realistic topography, which showed that resonance effectively occurred along the western coast of the island, where the water is deep and the continental shelf is narrow, and the resonance period was controlled by the ocean stratification strength and the shape of the island.

The Application and Antifouling of AEM-RS in Ocean Current Buoy

Equipped with type AEM-RS electromagnetic current meter, the buoy provided effective technical platform for on-site rapid monitoring of the ocean current. Performance index and usage in the ocean current buoy of AEM-RS was introduced. Ultrasonic cleaning method in seawater was developed for preventing AEM-RS from biofouling. Ocean current data can serve for oceanographic research and marine resource exploitation.

표면영상유속계(SIV)를 이용한 홍수유출량 측정

Abstract Surface Image Velocimetry(SIV) is an instrument to measure water surface velocity by using image processing techniques. Since SIV is a non-contact type measurement method, it is very effective and useful to measure water surface velocity for steep mountainous streams, such as streams in Jeju island. In the present study, a surface imaging velocimetry system was used to calculate the flow rate for flood event due to a typhoon. At the same time, two types of electromagnetic surface velocimetries (electromagnetic surface current meter and Kalesto) were used to observe flow velocities ​and compare the accuracies of each instrument. The comparison showed that for velocity distributions root mean square error(RMSE) was 0.33 and R-squared was 0.72. For discharge measurements, root mean square error(RMSE) reached 6.04 and R-squared did 0.92. It means that surface image velocimetry could be used as an alternative method for electromagnetic surface velocimetries in measuring flood discharge.Key words: SIV, Kalesto, electromagnetic surface current meter, Doppler radar, Surface velocity