Search

Our understanding of identifying and monitoring surge-type glacier distribution patterns, fluctuations, periodicities, and occurrence mechanism under the changing climate is challenging and scarce due to small numbers, limitations on the spatiotemporal coverage of remote sensing observations, and insufficient field-based glaciological data from the High Mountain Asia. The surging glaciers have caused major hazards, and their movement can destroy peripheral and downstream areas like roads, connecting bridges, villages, and hydropower stations and trigger a glacial lake outburst flood or form a dammed (moraine or ice) lake in High Mountain Asia (HMA) in the recent past. Many glaciers have experienced a mass loss and retreat due to ongoing climate change in HMA in recent decades, whereas studies conducted in the Karakorum, Pamir, Tien Shan, and Kunlun Shan regions have reported the surging of the glaciers. Whereas, in the central Himalayan region, very limited studies have been able to identify and explain in detail the surging glaciers and their surge mechanism. In this study, we identified an unnamed glacier surge in the central Himalaya, triggered between 12 September and 14 October 2019 (on a monthly scale) using multi-source high-resolution remote sensing data (CARTOSAT-1 [2011 and 2012], LISS-IV-2A [2011, 2017, and 2020], Landsat-5 [TM], 7 [ETM +], 8 [OLI/TIRS], and Sentinel [2A and 2B]) in conjunction with shuttle radar topography mission [SRTM], Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER], and High Mountain Asia digital elevation model (DEM) database. We used a series of algorithms package named MicMac ASTER (MMASTER) tool for generating DEMs from data of two telescopes for the estimation of the surface elevation change, and to calculate the surface velocity, we employed the "Co-registration of Optically Sensed Images and Correlation" (COSI-Corr), a Fourier-based, highly advanced matching program. Based on the observations of the glacier terminus fluctuation, surface velocity, and surface elevation change from 1993 to 2022, this study revealed that the unnamed glacier underwent a surge for the first time in the past three decades. The glacier's surface velocity increased from 7 ± 3 m year−1 during quiescence (2001–2002) to 163 ± 1 m year−1 during the surge (2019–2020) and then decreased to 17 ± 2 m year−1 between 2021 and 2022. Between 12 September and 14 October 2019, there was a sudden and significant increase in surface velocity of 863 m within a month (i.e., 27 m/day compared to the month prior), indicating the initiation of the surge. Overall, the present study results suggest that the glacier's velocity varied considerably during the observed period, with periods of gradual increase, sudden increase, and subsequent decrease. Further, the changes in glacier surface suggest a total mean elevation change of 0.26 ± 0.2 m year−1 between 2000 and 2020. In this study, we present novel observations of a glacier surge in the central Himalaya, compare its characteristics to surge-type glaciers reported elsewhere, and discuss the possible mechanisms controlling its behavior. [ABSTRACT FROM AUTHOR]

Water flow is an important piece of information in hydrological assessments, aiding in understanding variations in river flow and predicting its trends. Traditional contact-based methods for measuring water flow are greatly affected by environmental conditions during emergencies, with difficulties in installation and low measurement efficiency. To address this issue, this study explores a method for calculating video-based flow measurements using a non-contact spatio-temporal imaging approach. The study selects the Pukou section of the Chuhe River in Nanjing City as the experimental site for water flow detection. The detection method in this paper uses video flow measurement to measure the velocity of water flow. The collected data is processed visually and displayed on the interface of terminal equipment, and the collected data can be transmitted to a specified address in the format of the hydrological protocol. Experimental results indicate that using drones equipped with video flow measurement devices can rapidly and effectively complete water flow detection. The data can be displayed in a visual format on terminal equipment, facilitating viewing by relevant personnel. This form of detection is fast, safe, and environmentally adaptive, with the potential for practical applications. Further research into this detection method will promote the smart and integrated development of hydrological assessments. [ABSTRACT FROM AUTHOR]

2D hydrodynamic models deepen the understanding of hydromorphological processes in fluvial systems. UAV (Unoccupied Aerial Vehicles) can record complementary calibration and validation data for these models of large areas. In this study, we created a 2D hydrodynamic model of the Pulmanki River in Northern Finland under shallow, open‐channel conditions based on three calibration sets. We examined the potential of UAV‐flow velocities for model validation. Here, we applied a cross‐validation approach comprising the conversion from surface to depth‐averaged velocity and vice versa using fixed velocity coefficients (α). We further assessed the conversion performance including hydraulic variables to evaluate this coupled numerical‐experimental concept. Our model showed good performance in the three calibration runs for water level and depth‐averaged velocity. The calculation of surface to depth‐averaged velocity identified the coefficient α = 0.8 as the best choice with R2 = 0.62 for the straight river reach, indicating a good agreement between converted velocity and the reference data. A poor agreement, however, is evident for the meander section with R2 = 0.406. While there were no statistically significant relationships between the conversion performance and hydraulic variables, there were observable trends in the residuals indicating over‐ and underestimation of converted velocities, particularly in relation to bathymetry and distance to the channel centre, with variations based on the river structure. Our study demonstrates that UAV reference data has the potential to enhance 2D hydrodynamic models but particularly improves our understanding of spatial flow distribution. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the rock glacier destabilisation and permafrost thawing induced by warming climate represent a continuous threat to life, infrastructure and socio‐economic development in the mountainous regions of the Hindu Kush Himalaya. This study presents the first systematic rock glacier inventory for the Shigar and Shayok basins, quantifying rock glacier geomorphology and kinematics based on morphological evidence using Google Earth images and interferometric synthetic aperture radar (InSAR). The certainty index of each inventoried rock glacier is recorded, along with its geomorphological properties and kinematic attributes. The rock glacier velocity is estimated through the InSAR time series analysis of Sentinel‐1 images from 2020 to 2021, with temporal baselines at 12‐day intervals. We developed a rock glacier inventory consisting of 84 rock glaciers covering an area of 29 km2 for the Shigar Basin and 2206 rock glaciers encompassing 369 km2 for the Shayok Basin. Among these rock glaciers, 69% and 52% are categorised as active rock glaciers, respectively. Rock glaciers in both catchments are confined to elevations between 3600 and 5875 m a.s.l., with a mean area of 0.22 km2. The maximum recorded velocity for active rock glaciers in the Shigar Basin is 101 ± 9 cm year−1, with a median of 27 ± 10 cm year−1, and in the Shayok Basin 114 ± 10 cm year−1 (median of 29 ± 9 cm year−1). Temporal variations in the surface velocities of the rock glaciers reveal that they increase with rising temperatures in both catchments, highlighting the seasonality in the rock glacier surface velocity. In total, we recorded the kinematic attributes of 98% of the inventoried rock glaciers in the study area. [ABSTRACT FROM AUTHOR]

We study the implementation of a numerical method to solve the time fractional (2+1)-dimensional Wu–Zhang system focusing on properties of trigonometric basis functions (TBFs). The approximation of the system describing dispersive long waves by appropriate discretization of the system and Grünwald difference operators is discussed and a linear system of the resulting discrete systems is given. This process includes a presentation of a general framework to approximate the solution by a mesh-free scheme which is stable and converges. Finally, various numerical experiments are present to illustrate the exceptional effect of fractional-order on the WZ system.

Maritime glaciers in the southeastern Tibetan Plateau (TP) have experienced important changes in mass and dynamics over the past decades, challenging the regional water supply and glacier-related hazards. However, knowledge about long-term variations in the surface velocity and mass balance of maritime glaciers remains incomplete due to the lack of representative observations in the southeastern TP. In this study, offset tracking is employed to measure spatiotemporal variation in the surface velocity of the Hailuogou Glacier (HLG) in Mount Gongga of the southeastern TP using Sentinel-1A imagery, while the time series of the HLG mass balance is reconstructed since 1950 by a physically based energy–mass balance model. Our satellite-based results find that HLG surface velocity shows significant spatial heterogeneity with a double-peak pattern along the flow line, and sustained slowdown below the icefall zone has been observed during the past nearly 40 years, although the icefall zone and the area above it have become relatively active. Our modeling indicates a persistent increase in mass loss over the last seven decades with an average rate of −0.58 m water equivalent (w.e.) year−1, which has accelerated in the past two decades. Sustained slowdown on the glacier is concomitant with pronounced negative mass balance, thereby enhancing glacier wastage in recent decades. The long-term trend in HLG mass loss is mainly driven by an increase in positive air temperature that decreases surface albedo and solid precipitation ratio and increases longwave incoming radiation, besides the influence of supraglacial debris cover. Large-scale atmospheric circulation patterns in the Eurasian region provide important implications for regional-to-local climate variability, unsustainably intensifying the trend of the negative mass balance of the HLG in the southeastern TP in the past two decades. [ABSTRACT FROM AUTHOR]

We study the implementation of a numerical method to solve the time fractional (2 + 1) -dimensional Wu–Zhang system focusing on properties of trigonometric basis functions (TBFs). The approximation of the system describing dispersive long waves by appropriate discretization of the system and Grünwald difference operators is discussed and a linear system of the resulting discrete systems is given. This process includes a presentation of a general framework to approximate the solution by a mesh-free scheme which is stable and converges. Finally, various numerical experiments are present to illustrate the exceptional effect of fractional-order on the WZ system. [ABSTRACT FROM AUTHOR]

In the 2010s, a large freshening event similar to past Great Salinity Anomalies occurred in the Iceland Basin that has since propagated into the Irminger Sea. The source waters of this fresh anomaly were hypothesized to have come from an eastward diversion of the Labrador Current, a finding that has since been supported by recent modeling studies. In this study, we investigate the pathways of the freshwater anomaly using a purely observational approach: particle tracking using satellite altimetry-derived surface velocity fields. Particle trajectories originating in the Labrador Current and integrated forward in time entered the Iceland Basin during the freshening event at nearly twice the frequency observed prior to 2009, suggesting an increased presence of Labrador Current-origin water in the Iceland Basin and Rockall Trough during the freshening. We observe a distinct regime change in 2009, similar to the timing found in the previous modeling papers. These spatial shifts were accompanied by faster transit times along the pathways which led to along-stream convergence and more particles arriving to the eastern subpolar gyre. These findings support the hypothesis that a diversion of relatively fresh Labrador Current waters eastward from the Grand Banks can explain the unprecedented freshening in the Iceland Basin. [ABSTRACT FROM AUTHOR]

Several studies have evaluated the accuracy of ice thickness model inversions, but the effects of surface velocity and topographic factors have not been fully studied. Because of the important potential of models for estimating regional and global ice thickness, the influence of the characteristics of the glaciers themselves on the models is unknown. Therefore, we estimated the thickness of 10 glaciers in HMA based on remote sensing data using the GlabTop2, GV22, and VOLTA models, and we analyzed the factors affecting accuracy. The first two models are representative of the widely used shallow ice approximation and laminar flow theory, and the latter is a new model based on shallow ice approximation. The results show that the RMSEs for GlabTop2, VOLTA, and GV22 are 36.6 m, 56.8 m, and 63.2 m, respectively. The accuracy of the three models differed obviously under the influence of different slopes, aspects, and surface velocities. In contrast to glaciers with higher surface velocities, GV22 is more suitable for glaciers with smaller surface velocities, and the accuracy of the model is significantly reduced when surface velocities are greater than 50 m/yr. Aspect has an effect on the accuracy of the GV22 ice thickness inversion but not on the other models. Ice thicknesses estimated using the three models is more reliable at surface slopes of 16–24°. These three models do not apply to gentle glaciers such as icecaps. Our study provides an important reference for choosing a suitable model to invert the glacier thickness in HMA. [ABSTRACT FROM AUTHOR]

As a consequence of their natural occurrence and the frequent formation of multiple surges with high sediment loads, debris flows are considered one of the most hazardous gravity‐driven mass movements in mountain regions. Field measurements of surge dynamics are an essential link in the chain of understanding fundamental process dynamics and engineering protection against debris flows. However, continuous information on the velocities of multiple consecutive surges within a single debris‐flow event with high temporal resolution is rare. In this study, we present a new pulse‐Doppler radar (PD radar) for high‐resolution real‐time debris‐flow monitoring. We analyze PD radar data sets over a torrent length of 250 m for two debris flows that occurred at the Gadria creek (IT), on 26 July 2019 and 10 August 2020. The radar data were validated with independently derived data from particle image velocimetry and manually tracked velocities. We observe that between surges, the flow frequently comes to a complete halt and is re‐mobilized by subsequent surges, resembling erosion‐deposition waves in granular flows. In addition, our data confirm that surges can superimpose and merge. We anticipate that the outcomes of this work serve as a blueprint for future high‐resolution observations of debris‐flow surge dynamics with PD radar and that our findings provide new insights into the physical principles of natural debris flows. Plain Language Summary: Debris flows pose a severe threat to settlements and human life in mountainous regions. Typically triggered by violent thunderstorms, a mixture of heavy boulders, woody debris, and water quickly forms and rapidly begins to rush downhill at high velocity. Interestingly, a pulsating flow pattern can spontaneously develop, consisting of several consecutive waves, with the flow coming to a complete stop between waves. This phenomenon has already been studied by other researchers under laboratory conditions and using simulations. However, high‐resolution velocity measurements in the field are very rare. In this study, we present radar observations of two natural debris flows at the Gadria creek (Italy) to investigate how this behavior is reflected in reality. The insights we derived from our data sets can contribute significantly to the understanding of the process and are crucial for the management of this risk through safety measures. Key Points: PD radar velocity observations of debris flows were validated in a comparative analysis with DPIV and optical methodsPD radar data sets show that surges can superimpose and merge with one anotherThe events exhibited erosion‐deposition waves with quite similar surge metrics although Froude numbers were largely different [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) tomographic reconstruction in confined-space requires a mapping relationship which considers the refraction distortion caused by optical walls. In this work, a tomography method, namely full-field cross-interface computed tomography (FCICT), is proposed to solve confine-space problems. The FCICT method utilizes Snell's law and reverse ray-tracing to analytically correct imaging distortion and establishes the mapping relationship from 3D measurement domain to 2D images. Numerical phantom study is first employed to validate the FCICT method. Afterwards, the FCICT is applied on the experimental reconstruction of an illuminated two-phase jet flow which is initially generated inside an optical cylinder and then gradually moves outside. The comparison between accurately reconstructed liquid jet by FCICT and coarse result by traditional open space tomography algorithm provides a practical validation of FCICT. Based on the 3D liquid jet reconstructions at different time sequences, the distributions of surface velocity and 3D curvatures are calculated, and their correspondences are systematically analyzed. It is found that the velocity of a surface point is positively correlated with the mean curvature at the same point, which indicates the concavity/convexity of liquid jet surface is possibly in accordance with the surface velocity. Moreover, the surface velocity presents monotonical increasing trend with larger Gaussian curvature for elliptic surface points only, due to the dominated Brownian motion as the liquid jet develops. [ABSTRACT FROM AUTHOR]

The geometry of a compressor leading edge has an important effect on the aerodynamic performance at an off-designed incidence angle. The current geometric design methods of the leading edge are usually developed based on the flow characteristics at the designed incidence angle. However, few research focuses on the quantitative rules of the leading edge flow characteristics at the off-designed incidence angle in a compressor cascade. This situation restricts the further optimization and development of the leading edge geometry design method. In this paper, starting from the research of a potential cascade theory, the singularity point, where the surface velocity approaches infinity in the leading edge region, is eliminated by applying the characteristic that the ratio of the velocity increasement on the incidence angle in the plate cascade and the isolated plate flow is finite. Secondly, the equivalent pitch lengths based on 1/cos(β) and VI caused by a diffuser deceleration in the cascade passage were employed to correct the effect of the stagger angle. Finally, by introducing the isolated flow around the thick airfoil and considering the influence of the camber line geometry, a model of the variation of the surface velocity near the leading edge under the off-designed incidence angle, named the velocity increment on incidence angle, is derived from any compressor cascade. Hence, the relation between the off-designed incidence angle and the designed incidence angle of the surface velocity in a cascade blade is established, and it depends only on the geometrical parameters. Through a verification using numerical calculations and experimental measurement, the explicit formula for the velocity increment on incidence angle proposed in this paper has high precision near the leading edge. [ABSTRACT FROM AUTHOR]

The regional surge patterns and control mechanisms for glaciers in the western Pamirs are unclear. Using remote sensing, more surge-type glaciers have been discovered in the western Pamirs. This provides an opportunity to obtain the integral characteristics of glacier surging. Using Sentinel-1A, TSX/TDX and Landsat remote sensing data, the changes in surface velocity, surface elevation and surface features of five glaciers that have recently surged in the western Pamirs are obtained. The results show that (1) all glacier surges initiate gradually for several years and most form a surge front in the upper region of the glacier. (2) For most glaciers, the active phase of the surge is more than 2 years, except for one that is within several months. (3) The peak velocity mostly occurs in summer and autumn, and the maximum velocity is less than 8 m d−1. (4) There is sharp deceleration, such as the hydrologic controlled surge at the end of the surge. However, the surface flow of the transverse profiles shows no features of base sliding. Based on the comparison of surge patterns with other regions in High Mountain Asia, we conclude that the surging glaciers in the western Pamirs are triggered by thermal mechanisms under the control of sub-hydrological modulation. [ABSTRACT FROM AUTHOR]

Wave-orbital velocities are estimated with particle image velocimetry (PIV) applied to rapid sequences of images of the surfzone surface obtained with a low-cost camera mounted on an amphibious tripod. Time series and spectra of the remotely sensed cross-shore wave-orbital velocities are converted to the depth of colocated acoustic Doppler velocimeters (ADVs), using linear finite depth theory. These converted velocities are similar to the velocities measured in situ (mean nRMSE for time series = 16% and for spectra = 10%). Small discrepancies between depth-attenuated surface and in situ currents may be owing to errors in the surface velocity measurements, uncertainties in the water depth, the vertical elevation of the ADVs, and the neglect of nonlinear effects when using linear finite depth theory. These results show the potential to obtain spatially dense estimates of wave velocities using optical near-field remote methods during field campaigns and continuous monitoring operations. • Surfzone wave-orbital velocities are estimated with a low-cost camera and particle image velocimetry. • Surface velocities are converted to the equivalent velocity at the depth of the ADVs using linear finite depth theory. • Surface velocity spectra are similar (RMSE∼10%) to mid-water column spectra estimates when accounting for depth attenuation. [ABSTRACT FROM AUTHOR]

This review work presented a detailed review of snow cover area, mass balance status, glacial area loss, surface velocities and applications of snowmelt runoff model (SRM) applied in the Kashmir Himalayas and Upper Indus Basin (UIB) of the Himalayas. This study reviewed all the studies done in the past which are done on the Kashmir Himalayas and UIB glaciers by different methods. The geodetic and glaciological methods suggested that the glaciers in the Kashmir Himalayas and UIB are having a negative glacial mass balance and are losing ice mass at higher rates during the last two decades and are losing glacial area every year. And the glaciers in the Zanskar range are also having negative mass balance but are losing less ice mass as compared to the Glaciers in Kashmir Himalayas, while the glaciers in the Karakorum range are having positive mass balance and are losing glacial area at slower rates. Studies have found that higher surface velocities are observed in the glaciers which are present in the Kashmir region and indicate rapid melting because of higher temperatures recorded in this part of the world because of global warming. This review reflects an increasing understanding that how much of the water reservoirs we have lost and in which era we are heading to. [ABSTRACT FROM AUTHOR]

Ultra-wide slabs have a good application market and prospect, but there is still a lack of research on the flow field. To explore the characteristics of its flow field, this study built a 0.5-scale physical model of mold using Perspex. The effect of casting speed on flow field and surface flow speed was investigated by using an ink tracer experiment and contact measurement. There were various flow patterns in the ultra-wide slab mold, and they continue to transform each other. The jet momentum from the nozzle ports was diffused by colliding with the wide face, which lowered its kinetic energy and affected its subsequent diffusion. Compared with the conventional mold, the upper flow intensity of the ultra-wide slab mold was weaker, which made its liquid surface inactive and caused it to produce a flux rim or slag strip. At different casting speeds, the average flow speed distribution of the ultra-wide slab was C-shaped. When it increased from 0.9 to 1.4 m/s, the corresponding maximum average flow speed increased from 0.08 to 0.2 m/s. At the same time, the proportion of the low-flow speed zone at the most active part of the surface also gradually decreased from more than 90% to about 49%. [ABSTRACT FROM AUTHOR]

Considering that water flow energy affects the detachment of soil particles, the transport and deposit of the detached particles, the flow velocity is a key variable governing the soil erosion processes at the hillslope scale. The simple dye‐tracer technique for measuring mean flow velocity can be applied in non‐controlled field applications for which some measurement difficulties (e.g. due to sediment transport, and shallow flows) can occur. The correction factor is usually obtained as the ratio between the mean velocity, deriving from measurements of flow discharge and water depth, and surface velocity. Alternatively, the possibility of using the velocity profile in a given vertical to determine a suitable correction factor has not yet been explored. In this article, the flow velocity measurements were carried out in five verticals having a different distance from the wall of a flume whose bed was covered by hemispheres with different concentrations (9%–64%) and organized in two arrangements (square, staggered). Fifteen runs, characterized by different Reynolds and Froude numbers, were performed and the correction factor αvv was calculated for each vertical. For the axial vertical αvv was independent of the arrangement, decreased with the hemisphere concentration, and increased with both the Froude and Reynolds numbers. Furthermore, αvv decreased from the bank to the flume axis as a result of the varying shape of the velocity profile. The analysis showed that the frequency distributions of the ratio between αvv and its mean value αm were overlaid and αm was used to represent the correction factor, accordingly. A relation of αm with the distance from the flume wall was detected. For the measured velocity profiles having a power shape, the analysis also demonstrated that the αvv values, obtained by fitting the power law to the measurements, were close to both those calculated as the ratio between the mean velocity along the vertical and the surface velocity and their averaged values across the hydraulic section. These three methods give comparable average values of the correction factor, in the range of 0.72–0.75, which are close to the commonly applied value of 0.8. Finally, this investigation demonstrated that a single survey of a power velocity profile allows for obtaining the correction factor accounting for different verticals across the entire hydraulic section. [ABSTRACT FROM AUTHOR]

Accurate water flow measurement ensures proper irrigation water management by allocating the desired amount of water to the irrigation fields. The present study evaluated whether the non-intrusive smartphone application "DischargeApp" could be applicable and precise to measure small canal flow rates in the Koga irrigation Scheme. The app was tested in unlined canals with flow rates ranging from 15 to 65 l/s using a 90° V-notch weir. The app is found to overestimate high flow rates. Another source of uncertainty is that the app employed a constant surface velocity conversion factor (C = 0.8) to compute discharge. The accuracy was enhanced by recalculating the measured discharge using a new surface velocity conversion factor that depends on depths. The new conversion factor decreased the errors of MAE and RMSE by 47% and 52%, respectively. Where channel and other optional measuring techniques are not available without interfering with the flow operation conditions in place, the DischargeApp devices can be used to measure flows. The DischargeApp could be used to collect data using local citizens in data-scarce areas. This study suggested reconfiguring the DischargeApp with a new surface velocity conversion coefficient based on flow depths in field conditions for better performance. [ABSTRACT FROM AUTHOR]

In this article, physical and numerical simulation of the flow field in flexible thin slab caster funnel mold at high casting speed is carried out with a five-hole submerged entry nozzle (FHSEN), and characteristics of the flow field on funnel mold liquid level under different casting speeds (4, 5, and 6 m·min−1) and different submerged depths (130, 160, and 190 mm) are studied by comparing with the new submerged entry nozzle (NSEN) designed. Physical simulation is based on the funnel mold prototype. Numerical simulation is carried out based on FLUENT software, and industrial experiments of two kinds of submerged entry nozzle are also carried out. The results show that in the case of both physical and numerical simulation, the maximum surface velocity of the FHSEN funnel mold is 0.58 m·s−1, and the funnel mold liquid level is prone to slag entrapment. The NSEN funnel mold’ maximum surface velocity is 0.37 m·s−1. Compared with the FHSEN, the NSEN funnel mold’ maximum surface velocity decreases by 0.21 m·s−1, and funnel mold surface velocity decreases significantly. Finally, the accuracy of simulation results is verified by industrial tests, and it is also show that NSEN can greatly reduce funnel mold surface velocity and probability of slag entrapment.

Although there are few blockages on the wall of the nozzle, more inclusions are gathered at the bottom of the nozzle (zone 1) and at the front and rear of the nozzle outlet (zone 2), which is consistent with the analysis results. When the inclusions follow the molten steel to these two zones, the residence time of the inclusions increases, which constantly collides with the nozzle wall leading to adhere to the walls of the nozzle. Keywords: clogging; inclusion; level fluctuation; submerged entry nozzle; surface velocity EN clogging inclusion level fluctuation submerged entry nozzle surface velocity 1027 1033 7 11/02/22 20221001 NES 221001 1 Introduction A submerged entry nozzle (SEN) is an important functional refractory connecting tundish and mold. [Extracted from the article]

Himalayan glaciers are distinct by their surface characteristics, such as debris-cover, supra/proglacial lakes, ice-cliff, and tributaries' contributions, thus complicating their surface velocity pattern and their response towards climate warming. While remote sensing and modelled surface velocity estimation are valuable on a larger scale, in situ high-resolution data is crucial to validate them. In this study, four glaciers (Batal, Sutri Dhaka, Samudra Tapu, and Gepang Gath) from Chandra Basin were monitored to measure point-wise surface displacement using a static GNSS system during 2017–2018. Among them, the highest surface velocity was observed over Samudra Tapu (∼64.3 ma−1), a large and clean-type glacier, while the lowest was for Batal (∼6.2 ma−1), a small and debris-covered glacier. Our study highlighted the contrasting behaviour of lake-terminating and debris-covered glaciers for the surface velocity and also emphasize the additional control of the slope, supraglacial lake, debris thickness and convergence of glacier channels on the glacier surface velocity. [ABSTRACT FROM AUTHOR]

The large-scale particle image velocimetry (LSPIV) technique was regarded as a novel approach for estimating dam breach discharge in recent years. In order to investigate its advantages and disadvantages in the estimation of the dam breach hydrograph, the landslide dam breach experiments were conducted in a large width flume (4 m wide), and the relationship between the breach discharge and the surface velocity during the dam break process was also discussed. It was found that the LSPIV approach showed improved accuracy over the conventional volume conservation method in the estimation of the dam breach hydrograph, and the LSPIV approach was capable of capturing the prompt response of the hydrograph to the abrupt breach channel enlargement caused by the lateral collapse. To eliminate the error induced by the logarithmic approximation, the discharge obtained by the LSPIV approach at each time step should multiply a uniform factor of 1.08, which was proposed based on the total mass conservation concept. The methodology established in this study can be extended to measure the hydrograph of a prototype-scale dam breach flow, which is important for disaster mitigation but only difficult to measure in the field. [ABSTRACT FROM AUTHOR]

Water velocity and discharge are essential parameters for monitoring water resources sustainably. Datasets acquired from Unoccupied Aerial Systems (UAS) allow for river monitoring at high spatial and temporal resolution, and may be the only alternative in areas that are difficult to access. Image or video-based methods for river flow monitoring have become very popular since they are not time-consuming or expensive in contrast to traditional methods. This study presents a non-contact methodology to estimate streamflow based on data collected from UAS. Both surface velocity and river geometry are measured directly in field conditions via the UAS while streamflow is estimated with a new technique. Specifically, surface velocity is estimated by using image-based velocimetry software while river bathymetry is measured with a floating sonar, tethered like a pendulum to the UAV. Traditional field measurements were collected along the same cross-section of the Aggitis River in Greece in order to assess the accuracy of the remotely sensed velocities, depths, and discharges. Overall, the new technique is very promising for providing accurate UAV-based streamflow results compared to the field data. [ABSTRACT FROM AUTHOR]

The longest time series of surface velocities recorded on a rock glacier in the French Alps, covering more than three decades, has been recorded since 1983 on the Laurichard rock glacier (Ecrins range). The time signal of velocity changes is extracted from variance analyses separating time and space variabilities on the rock glacier surface to provide an average‐wide time signal. We show that changes in velocity from year to year are virtually uniform at all locations with homogeneous accelerations or decelerations on the scale of the rock glacier as a whole. The spatial structure of velocity was found to be nearly at steady state over 35 years. Nonlinear effects are located in low‐velocity areas such as the rock glacier margins where accelerations/decelerations tend to be proportional to the local velocity. Over the period of record, a long‐term trend in rock glacier acceleration was detected with a rate of +0.2 m/yr per decade. Two main phases of acceleration were identified from the mid‐1980s to 1999 and from 2010 to 2015. In between, those two periods were interrupted by a 10‐year period of almost steady‐state velocities with an abrupt deceleration from 2006 to 2009 of −0.35 m/yr. The process of internal increases in ice temperatures alone (and associated changes in creep rates) would seem insufficient to explain the long‐term rise of surface velocities and their annual variations. Changes in the liquid water are a possible contributing factor, due to the injection of seasonal water caused by melting snow cover or internal melt due to heat generated by enhanced ice creep and friction in the ice/debris mixture. [ABSTRACT FROM AUTHOR]

Measurement of river discharge should be accurate, as it is key environmental data and essential for hydrologic simulations, regardless of whether the flow is high, medium, or low. Herein, conventional methods based on velocity measurements at different depths (i.e., one‐point method, two‐point method, and three‐point method) are evaluated with a method using a surface velocity index and a method based on the entropy theory to estimate river discharge. All the methods were implemented to calculate the discharge of Agios Germanos River, located in Northern Greece, based on 2 years of measurement. Considering that the uncertainty in flow measurement is decreasing by increasing the number of velocity measurements points (EN ISO, 2007), in this work, the reference method is the conventional three‐point method. Results show that the other two conventional methods (the one‐point and the two‐point) estimate the discharge with an error of about 3%, while the error of the other two methods ranges between 11 and 14%. Nevertheless, the nonconventional methods could be considered acceptable and could be used safely to minimize time and subsequently, the cost of field measurements. [ABSTRACT FROM AUTHOR]

Influenced by the Indian monsoon, the Kangri Karpo Mountains (KKM) of the southeastern Tibetan Plateau is the most humid part of the plateau, and one of the most important regions with numerous monsoon temperate glaciers. Glacier mass balance estimates have been strongly negative in the KKM over recent decades, but the spatiotemporal characteristics of surface velocity are poorly understood. Using phase-correlation feature tracking on Landsat images, this study estimates spatiotemporal variabilities of monsoon temperate glaciers for the period of 1988–2019. Results show that a significant slowdown was observed below an elevation of 4900 m, while an accelerated ice flow was found at an elevation of 4900–5800 m over the past 30 years. The trend of slowdown was −0.1 m a−1 dec−1 during 1988–2000, and then it increased to −0.5 m a−1 dec−1 during 2001–2019.

This study focused on the analysis of the time variability of the morphology of the Drygalski ice tongue (DIT), Antarctica, using – for the first time – satellite synthetic aperture radar (SAR) images. A time series of Sentinel-1 interferometric wide swath SAR imagery collected from 2016 to 2021 is considered and an unsupervised methodology, based on a global threshold constant false alarm rate approach, is used to extract the boundary between the DIT and the surrounding ice-free/ice-infested sea water. The most prominent rifts/fractures identified on the extracted profiles and the ice front are selected to analyse the DIT time variability. The feature tracking allows deriving information on the morphological evolution of the DIT, including the annual displacement and average surface velocity. Experimental results show that the DIT ice front calls for a relatively stable motion trend towards the sea with an average surface velocity of about 670 m per year. Our outcomes show a fairly good agreement with similar studies appeared in the scientific literature, which are mostly based on optical imagery. [ABSTRACT FROM AUTHOR]

This paper presents the application of an artificial neural network (ANN) to develop a model able to predict the holdup of a two-phase flow composed of water and mineral oil in a horizontal pipe. The surface velocities of each fluid and the pressure differential in the pipe are used as input parameters of the multi-layer artificial neural network with backpropagation, while the volumetric fraction of the fluids is used as an output parameter in the training. The 56 experimental data were obtained in the laboratory LabPetro-CEPETRO-UNICAMP. The results of the predictive model with the best performance show a mean absolute error (AAPE) of 3.01 % and a coefficient of determination R² of 0.9964, using 15 neurons in the hidden layer of the network and the TanSig transfer function. [ABSTRACT FROM AUTHOR]

We develop a maximum-entropy method for streamflow estimation from surface velocities. Entropy maximization, with mean and variance constraints, yields a mass and momentum conserving, error-function-type velocity profile. That sigmoidal profile's infinite branch shapes the hydrometrically critical free-surface region unphysically, so we derive approximate relationships of the ratio of the mean velocity V to the surface velocity v s u r f , f v = V / v s u r f , as function of β = E v 2 / V 2 (E = expectation); β is tightly estimable: β ≈ 1.01–1.15, fv ≈ 0.9–0.72. fv(β) is adaptable to the site geometry and roughness (i.e. to the local hydraulics, instead of the default fv = 0.86), improving the parsimonious discharge estimation from surface velocities. Laboratory data verify the concept. Tests at cross-sections of streams, with known variable bathymetry and roughness, demonstrate the method's ability to estimate the discharge solely from surface-velocity observations, with ± 5% accuracy referenced to discharge determined from densely sampled in-stream velocities. [ABSTRACT FROM AUTHOR]

Glacier change monitoring provides a significant understanding of glacier health and its influence on freshwater availability. Therefore, we have utilized remotely sensed data to estimate the glacier characteristics, mass balance, and volume change during 2013–2019 over the Sutri Dhaka and Batal glaciers, Chandra basin, western Himalayas. The glacier feature classification and shifting in isoline were mapped on a spatio-temporal scale. Furthermore, the surface velocity was measured using Coregistration of Optically Sensed Images and Correlation (COSI-Corr) and then used for estimating the ice thickness. The estimated velocity was compared with the stake observations and National Aeronautics and Space Administration (NASA)- Inter-Mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) data. Further, the glaciers' geodetic mass balance and volume change were calculated, indicating an average value of −0.03 ± 0.5, −0.34 ± 0.40 and −0.13 ± 0.14 m water equivalent (w.e.) year−1 during 2000–2009, 2009–2020, and 2000–2020, respectively. This multidimensional analysis of the glaciers is critical, as the meltwater from both glaciers contributes to the Chandra basin and also influences the local ecosystem. [ABSTRACT FROM AUTHOR]

The geometry of a compressor leading edge has an important effect on the aerodynamic performance at an off-designed incidence angle. The current geometric design methods of the leading edge are usually developed based on the flow characteristics at the designed incidence angle. However, few research focuses on the quantitative rules of the leading edge flow characteristics at the off-designed incidence angle in a compressor cascade. This situation restricts the further optimization and development of the leading edge geometry design method. In this paper, starting from the research of a potential cascade theory, the singularity point, where the surface velocity approaches infinity in the leading edge region, is eliminated by applying the characteristic that the ratio of the velocity increasement on the incidence angle in the plate cascade and the isolated plate flow is finite. Secondly, the equivalent pitch lengths based on 1/cos(β) and VI caused by a diffuser deceleration in the cascade passage were employed to correct the effect of the stagger angle. Finally, by introducing the isolated flow around the thick airfoil and considering the influence of the camber line geometry, a model of the variation of the surface velocity near the leading edge under the off-designed incidence angle, named the velocity increment on incidence angle, is derived from any compressor cascade. Hence, the relation between the off-designed incidence angle and the designed incidence angle of the surface velocity in a cascade blade is established, and it depends only on the geometrical parameters. Through a verification using numerical calculations and experimental measurement, the explicit formula for the velocity increment on incidence angle proposed in this paper has high precision near the leading edge.

The mechanical properties of glacier beds play a fundamental role in regulating the sensitivity of glaciers to environmental forcing across a wide range of timescales. Glaciers are commonly underlain by deformable till whose mechanical properties and influence on ice flow are not well understood but are critical for reliable projections of future glacier states. Using synoptic-scale observations of glacier motion in different seasons to constrain numerical ice flow models, we study the mechanics of the bed beneath Hofsjökull, a land-terminating ice cap in central Iceland. Our results indicate that the bed deforms plastically and weakens following incipient summertime surface melt. Combining the inferred basal shear traction fields with a Coulomb-plastic bed model, we estimate the spatially distributed effective basal water pressure and show that changes in basal water pressure and glacier accelerations are non-local and non-linear. These results motivate an idealized physical model relating mean basal water pressure and basal slip rate wherein the sensitivity of glacier flow to changes in basal water pressure is inversely related to the ice surface slope.

The acceleration of surface velocities observed over the last two decades on monitored rock glaciers worldwide is a widespread signal of the probable control of warming air temperatures on long‐term permafrost creep. Yet, the actual consequences of this acceleration on sediment availability in high mountain catchments have never been properly estimated at the pluri‐decadal scale. The present study evaluates the sediment transfer activity between five rock glaciers located in the western European Alps and the headwaters of the torrential channels they are respectively connected to. It reposes on the orthorectification of aerial images available generally from the 1960s to the mid‐2010, to reconstruct time‐series of (i) horizontal surface velocities and (ii) frontal erosion rates. Values of horizontal velocity are retrieved by tracking the displacement of boulders on the surface of rock glaciers between consecutive images while erosion rates affecting the fronts are calculated by combining these values of displacement with the geometry of the front (mean width and rock glacier thickness) derived from recent high‐resolution digital elevation models. Results confirm the general acceleration of rock glaciers surface velocities since the 1970s and indicate that this accelerating trend is causing an increase in the erosion rates calculated at the front of most studied rock glaciers. In some cases and over specific periods however, the acceleration resulted in the advance of the whole landforms over their own sediments, leading to a comparatively low sediment export towards the torrents. [ABSTRACT FROM AUTHOR]

Large-scale image velocimetry is a novel approach for non-contact remote sensing of flow in rivers. Research within this topic has largely focussed on developing specific aspects of the image velocimetry work-flow, or alternatively, testing specific tools or software using case studies. This has resulted in the development of a multitude of techniques, with varying practice being employed between groups, and authorities. As such, for those new to image velocimetry, it may be hard to decipher which methods are suited for particular challenges. This research collates, synthesises, and presents current understanding related to the application of particle image velocimetry (PIV) and particle tracking velocimetry (PTV) approaches in a fluvial setting. The image velocimetry work-flow is compartmentalised into sub-systems of: capture optimisation, pre-processing, processing, and post-processing. The focus of each section is to provide examples from the wider literature for best practice, or where this is not possible, to provide an overview of the theoretical basis and provide examples to use as precedence and inform decision making. We present literature from a range of sources from across the hydrology and remote sensing literature to suggest circumstances in which specific approaches are best applied. For most sub-systems, there is clear research or precedence indicating how to best perform analysis. However, there are some stages in the process that are not conclusive with one set method and require user intuition or further research. For example, the role of external environmental conditions on the performance of image velocimetry being a key aspect that is currently lacking research. Further understanding in areas that are lacking, such as environmental challenges, is vital if image velocimetry is to be used as a method for the extraction of river flow information across the range of hydro-geomorphic conditions.

Accurate water flow measurement ensures proper irrigation water management by allocating the desired amount of water to the irrigation fields. The present study evaluated whether the non-intrusive smartphone application “DischargeApp” could be applicable and precise to measure small canal flow rates in the Koga irrigation Scheme. The app was tested in unlined canals with flow rates ranging from 15 to 65 l/s using a 90° V-notch weir. The app is found to overestimate high flow rates. Another source of uncertainty is that the app employed a constant surface velocity conversion factor (C = 0.8) to compute discharge. The accuracy was enhanced by recalculating the measured discharge using a new surface velocity conversion factor that depends on depths. The new conversion factor decreased the errors of MAE and RMSE by 47% and 52%, respectively. Where channel and other optional measuring techniques are not available without interfering with the flow operation conditions in place, the DischargeApp devices can be used to measure flows. The DischargeApp could be used to collect data using local citizens in data-scarce areas. This study suggested reconfiguring the DischargeApp with a new surface velocity conversion coefficient based on flow depths in field conditions for better performance.

Abstract In order to investigate the relationship between water surface velocity and breach hydrograph, a series of dam breach experiments with a generalised landslide dam were conducted in an open channel of 50 m × 4 m × 2 m. The large‐scale particle image velocimetry (LSPIV) technique was applied to measure the time history of water surface velocity during the dam breach process, and the hydrography was obtained by integrating the surface velocity along the water depth. The influence of different vertical velocity profile approximation and suspended sediment concentration on the peak breach discharge were analysed and discussed. The results showed that the water depth over the breach crest can be described as a function of water surface velocity using d¯t=k22u¯surf2/k1g. A simple formula based on surface velocity and breach width for the estimation of breach discharge was further proposed and verified.

In order to investigate the relationship between water surface velocity and breach hydrograph, a series of dam breach experiments with a generalised landslide dam were conducted in an open channel of 50 m × 4 m × 2 m. The large‐scale particle image velocimetry (LSPIV) technique was applied to measure the time history of water surface velocity during the dam breach process, and the hydrography was obtained by integrating the surface velocity along the water depth. The influence of different vertical velocity profile approximation and suspended sediment concentration on the peak breach discharge were analysed and discussed. The results showed that the water depth over the breach crest can be described as a function of water surface velocity using d¯t=k22u¯surf2/k1g. A simple formula based on surface velocity and breach width for the estimation of breach discharge was further proposed and verified. [ABSTRACT FROM AUTHOR]

We develop Bayesian statistical models that are designed for the inference of ice softness and basal sliding parameters, important glaciological quantities. These models are applied to Langjökull, the second largest temperate ice cap in Iceland at about 900 squared kilometers in area. The models make use of a relationship between physical parameters and ice velocity as stipulated by a shallow ice approximation that is generally applicable to Langjökull. The posterior distribution for ice softness concentrates around 18.2 × 10−25s−1Pa−3; moreover, spatially varying basal sliding parameters are inferred allowing for the decomposition of velocity into a deformation component and a sliding component, with spatial variation consistent with previous studies. Bayesian computation is conducted with a Gibbs sampling approach. The paper serves as an example of statistical inference for ice softness and basal sliding parameters at temperate, shallow glaciers using surface velocity data.

Water velocity and discharge are essential parameters for monitoring water resources sustainably. Datasets acquired from Unoccupied Aerial Systems (UAS) allow for river monitoring at high spatial and temporal resolution, and may be the only alternative in areas that are difficult to access. Image or video-based methods for river flow monitoring have become very popular since they are not time-consuming or expensive in contrast to traditional methods. This study presents a non-contact methodology to estimate streamflow based on data collected from UAS. Both surface velocity and river geometry are measured directly in field conditions via the UAS while streamflow is estimated with a new technique. Specifically, surface velocity is estimated by using image-based velocimetry software while river bathymetry is measured with a floating sonar, tethered like a pendulum to the UAV. Traditional field measurements were collected along the same cross-section of the Aggitis River in Greece in order to assess the accuracy of the remotely sensed velocities, depths, and discharges. Overall, the new technique is very promising for providing accurate UAV-based streamflow results compared to the field data.

Image cross‐correlation techniques, such as particle image velocimetry (PIV), can estimate water surface velocity (vsurf) of streams. However, discharge estimation requires water depth and the depth‐averaged vertical velocity (Um). The variability of the ratio Um/vsurf introduces large errors in discharge estimates. We demonstrate a method to estimate vsurf from Unmanned Aerial Systems (UASs) with PIV technique. This method does not require any ground control point (GCP): the conversion of velocities from pixels per frame into length per time is performed by informing a camera pinhole model; the range from the pinhole to the water surface is measured by the drone‐borne radar. For approximately uniform flow, Um is a function of the Gauckler‐Manning‐Strickler coefficient (Ks) and vsurf. We implement an approach that can be used to jointly estimate Ks and discharge by informing a system of two unknowns (Ks and discharge) and two nonlinear equations: i) Manning's equation and ii) mean‐section method for computing discharge from Um. This approach relies on bathymetry, acquired in situ a priori, and on UAS‐borne vsurf and water surface slope measurements. Our joint (discharge and Ks) estimation approach is an alternative to the widely used approach that relies on estimating Um as 0.85·vsurf. It was extensively investigated in 27 case studies, in different streams with different hydraulic conditions. Discharge estimated with the joint estimation approach showed a mean absolute error of 19.1% compared to in situ discharge measurements. Ks estimates showed a mean absolute error of 3 m1/3/s compared to in situ measurements. Key Points: Drone‐borne sensors can measure stream water surface velocity and water surface slopeWe developed a new method to estimate stream roughness and discharge from drone‐borne water surface velocity and slope measurementsDrone‐borne discharge measurements compared well with in situ measurements in 27 different field sites [ABSTRACT FROM AUTHOR]

Influenced by the Indian monsoon, the Kangri Karpo Mountains (KKM) of the southeastern Tibetan Plateau is the most humid part of the plateau, and one of the most important regions with numerous monsoon temperate glaciers. Glacier mass balance estimates have been strongly negative in the KKM over recent decades, but the spatiotemporal characteristics of surface velocity are poorly understood. Using phase-correlation feature tracking on Landsat images, this study estimates spatiotemporal variabilities of monsoon temperate glaciers for the period of 1988–2019. Results show that a significant slowdown was observed below an elevation of 4900 m, while an accelerated ice flow was found at an elevation of 4900–5800 m over the past 30 years. The trend of slowdown was −0.1 m a−1 dec−1 during 1988–2000, and then it increased to −0.5 m a−1 dec−1 during 2001–2019. [ABSTRACT FROM AUTHOR]

We demonstrate a 24 GHz hydrology radar system. The continuous‐wave Doppler radar is capable of noncontact and wide‐range surface‐flow velocity detection in various scenarios. The radar receives the reflected echo signal through a directional narrow‐beam antenna. After amplification and demodulation by the proposed low‐noise amplifier and the subharmonic down‐conversion mixer, respectively, the Doppler frequency‐shift is analyzed by the digital signal processing (DSP) module for estimation of the water flow velocity. Moreover, for water level detection, a phase‐locked loop with micro control unit (MCU)‐controlled division ratio is included in the RF module for generating a stable and tunable (or frequency modulation) 24‐GHz‐band transmitting signal with low phase noise. To verify the radar system, outdoor field tests have been conducted. The measured results are consistent with the theoretical values, and the results of both the float method and the commercial handheld (Stalker Pro II) surface velocity radar. In the condition of water ripple lower than 3 cm, the radar functions well for flow speed range of 0.3 ~ 34.6 m/s. Overall, the hydrology radar is suitable for surface‐flow velocity detection (especially in bad weather) and water resource management (such as water‐level detection). [ABSTRACT FROM AUTHOR]

The objective was to evaluate effects of structural design, particle size and filter media height on pressure loss and surface velocity in the expanding filter layer during the backwashing process. The hydraulic behaviour of three commercial sand filter designs were compared. Experiments were conducted in an experimental closed circuit module. The treatments were based on the evaluation of three sand particle sizes combined with three filter bed heights for each filter design. The results showed that for the evaluated sand filters, with their different drainage structures in terms of area and arrangements, had different hydraulic behaviours during the backwashing. Coarser sand particles and greater filter layer heights produced larger slopes in the surface velocity curves as a function of percentage of filter bed expansion. No difference was observed in the minimum fluidisation velocity with changing the filter media heights, but an increase in the minimum fluidisation velocity was observed with increasing sand particle size. Filter beds composed of coarse sand particles and low filter bed heights produced lower increases in the pressure loss with increasing backwash surface velocity. Determining the minimum fluidisation velocity using the graphical analysis method to determine the pressure loss across the filter bed proved to be a reliable method for evaluating the equipment used. • We evaluated different commercial sand filter models. • Different sand filter drainage led to heterogeneous hydraulic behaviours. • The use of coarser particles and lower layer heights led to lower pressure loss. [ABSTRACT FROM AUTHOR]

Marangoni drying is widely employed in integrated circuit manufacturing to remove water from the wafer surface. The organic vapor blown at the meniscus induces a strong Marangoni effect, which strips the entrained water film induced by the wafer's withdrawal from a deionization water bath, and realizes ultra-clean drying of the wafer. The present work implements a numerical investigation of the terminal residual film and free surface flow in the water entrainment region during Marangoni drying based on a trans-scale model containing the thin water film, meniscus, and bulk region. The results show that the terminal thickness of the water film is 30 nm, which approximately agrees with the previous experimental and numerical results. In addition, the stagnation point moves away from the thin film region compared with that of wafer withdrawn in the absence of the Marangoni effect. The magnitude of free surface velocity in the thin film region after drying depends only on the withdrawal velocity, and is irrelevant to the Marangoni number. The analyses of the entrained water film thinning and surface flow provide useful guidance about controlling the drying process. [ABSTRACT FROM AUTHOR]

• A novel technique is developed for measuring the free surface and surface velocity. • Measurement accuracy is verified by wave probes, planes and fringe projection method. • The measurement technique is applied to the flood propagation in a compound channel. River flooding can pose a significant threat to people's lives and properties on the floodplain. Due to the difficulty and potential danger of monitoring field river floods, laboratory experiments have become the main and key method for exploring flood propagation and evaluating potential flood risks. However, the complex three-dimensional flow state of floods in the compound channel makes current measurement techniques inadequate for meeting monitoring requirements. To this end, a new technique is developed in this study that can simultaneously monitor the flood free surface and the surface velocity in the laboratory compound channel. The developed measurement technique combines stereoscopy and the particle tracking velocimetry (PTV) method through the pixel coordinate fitting method, so that the coordinates of the tracer particles can be reconstructed in the three-dimensional state. This method can not only increase the basic data in the free surface construction but can also capture the complex three-dimensional flood flow behavior. The proposed technology was applied to measure the free surface of flood propagation in a laboratory compound channel. Water level, flow velocity, wave velocity, and wave height were simultaneously measured. The measurement accuracy was verified using wave probes, spatial planes, and fringe projection techniques. The results indicate that the water level measurement error is approximately 1.6 mm, and the flow velocity measurement error is around 3 %. The developed measurement system is simpler than previous methods based on light reflection or absorption. Most importantly, it can simultaneously measure both the flood free surface and surface velocity by only sowing tracer particles on the water surface. The current measurement technology offers a new tool for studying flood propagation in a laboratory compound channel. [ABSTRACT FROM AUTHOR]