Fan Region Research Articles

Strontium Isotopic Composition as Tracers for Identifying Groundwater Recharge Sources in the Choushui River Alluvial Plain, Western Taiwan

Groundwater is a vital resource in the Chuoshui River alluvial plain (CSAP), a key agricultural area in Taiwan. Understanding groundwater recharge is crucial for sustainable water management amidst changing climatic conditions and increasing water demand. This study investigates the major ion composition, solute Sr concentrations, and 87Sr/86Sr ratios in groundwater and stream water from the Choushui River (CSR) to trace groundwater recharge sources. The Piper diagram reveals that most groundwater samples are of the freshwater Ca–HCO3 type, aligning with the total dissolved solids (TDS) classification. TDS and major ion compositions indicate that groundwater near Baguashan Terrace (BGT) and Douliu Hill (DLH) primarily derives from stream water and rainwater. Na+ and Cl− enrichment in some aquifers of BGT and DLH is attributed to the dissolution of paleo-sea salt and mixing with paleo-seawater from sedimentary porewater. Elevated dissolved Sr concentrations and lower 87Sr/86Sr ratios in these aquifers further support the intrusion of paleo-seawater. Groundwater in the proximal fan shows high TDS due to intensive weathering, complicating the use of TDS as a tracer. Sr isotopic compositions and solute Sr2+ concentrations effectively distinguish recharge sources, revealing that the CSR mainstream primarily recharges the proximal fan and BGT region, while CSR tributaries and rainwater mainly recharge the DLH region. This study concludes that Sr isotopic compositions and solute Sr2+ concentrations are more reliable than TDS and major ion compositions in identifying groundwater recharge sources, enhancing our understanding of groundwater origins and the processes affecting water quality.

Polarized Synchrotron Foreground Assessment for CMB Experiments

Polarized Galactic synchrotron emission is an undesirable foreground for cosmic microwave background experiments observing at frequencies <150 GHz. We perform a combined analysis of observational data at 1.4, 2.3, 23, 30, and 33 GHz to quantify the spatial variation of the polarized synchrotron spectral index, β pol, on ∼3.°5 scales. We compare results from different data combinations to address limitations and inconsistencies present in these public data, and form a composite map of β pol. Data quality masking leaves 44% sky coverage (73% for ∣b∣ > 45°). Generally −3.2 < β pol ≲ −3 in the inner Galactic plane and spurs, but the Fan Region in the outer galaxy has a flatter index. We find a clear spectral index steepening with increasing latitude south of the Galactic plane with Δβ pol = 0.4, and a smaller steepening of 0.25 in the north. Near the south Galactic pole the polarized synchrotron spectral index is β pol ≈ −3.4. Longitudinal spectral index variations of Δβ pol ∼ 0.1 about the latitudinal mean are also detected. Within the BICEP2/Keck survey footprint, we find consistency with a constant value, β pol = −3.25 ± 0.04 (statistical) ±0.02 (systematic). We compute a map of the frequency at which synchrotron and thermal dust emission contribute equally to the total polarized foreground. The limitations and inconsistencies among data sets encountered in this work make clear the value of additional independent surveys at multiple frequencies, especially between 10 and 20 GHz, provided these surveys have sufficient sensitivity and control of instrumental systematic errors.

Impacts of basin-wide irrigation pumping on dry-period stream baseflow in an alluvial aquifer in the Kosi Fan region of India and Nepal

Impacts of basin-wide irrigation pumping on dry-period stream baseflow in an alluvial aquifer in the Kosi Fan region of India and Nepal

A Unified Model for the Fan Region and the North Polar Spur: A Bundle of Filaments in the Local Galaxy

Abstract We present a simple, unified model that can explain two of the brightest, large-scale, diffuse, polarized radio features in the sky, the North Polar Spur (NPS) and the Fan Region, along with several other prominent loops. We suggest that they are long, magnetized, and parallel filamentary structures that surround the Local arm and/or Local Bubble, in which the Sun is embedded. We show that this model is consistent with the large number of observational studies on these regions and is able to resolve an apparent contradiction in the literature that suggests that the high-latitude portion of the NPS is nearby, while lower-latitude portions are more distant. Understanding the contributions of this local emission is critical to developing a complete model of the Galactic magnetic field. These very nearby structures also provide context to help understand similar nonthermal, filamentary structures that are increasingly being observed with modern radio telescopes.

The Global Magneto-ionic Medium Survey: A Faraday Depth Survey of the Northern Sky Covering 1280–1750 MHz

Abstract The Galactic interstellar medium hosts a significant magnetic field, which can be probed through the synchrotron emission produced from its interaction with relativistic electrons. Linearly polarized synchrotron emission is generated throughout the Galaxy and, at longer wavelengths, modified along nearly every path by Faraday rotation in the intervening magneto-ionic medium. Full characterization of the polarized emission requires wideband observations with many frequency channels. We have surveyed polarized radio emission from the Northern sky over the range 1280–1750 MHz, with channel width 236.8 kHz, using the John A. Galt Telescope (diameter 25.6 m) at the Dominion Radio Astrophysical Observatory, as part of the Global Magneto-Ionic Medium Survey. The survey covered 72% of the sky, decl. −30° to +87° at all R.A. The intensity scale was absolutely calibrated, based on the flux density and spectral index of Cygnus A. Polarization angle was calibrated using the extended polarized emission of the Fan Region. Data are presented as brightness temperatures with angular resolution 40′. Sensitivity in Stokes Q and U is 45 mK rms in a 1.18 MHz band. We have applied rotation measure synthesis to the data to obtain a Faraday depth cube of resolution 150 rad m−2 and sensitivity 3 mK rms of polarized intensity. Features in Faraday depth up to a width of 110 rad m−2 are represented. The maximum detectable Faraday depth is ±2 × 104 rad m−2. The survey data are available at the Canadian Astronomy Data Centre.

2D Analysis for Computing Supersonic and Subsonic Flow Field by Using Schlieren Light.(Dept.M)

A new 2D analysis of light for computing the Mach number distribution in a flow field from Schlieren images taken across the shock wave and expansion zone is proposed and verified by a 2D numerical computation Specially, inserting experimental measuring sensors inside shock wave zone and associated flow field is difficult. Across the shock wave, the pressure and density of the fluid change at extremely high rates, which affect the light refraction. The intensity of the Schlieren light is a function of the medium density, which is a function of the light ray path position. The contrast of each pixel is determined by analyzing the image. The equations of Schlieren intensity light are derivated to be a function of Mach number. These functions are applied on an image of shockwave around hemisphere-cylinder at M=1.96. To verify the results two-dimensional Navier-Stokes equations and conservation of energy equation are used to model the flow field and determine Mach number distribution around a hemisphere-cylinder of the supersonic flow, shock waves and associated flow field at the same previous conditions. The governing equations are discretized on a structured grid using an upwind difference scheme. The computational and experimental results show that there is a good matching in the iso-contour of the Mach number with difference less than 3%. The new proposed technique successfully represents the upstream region, the shock wave region, the subsonic region and the expansion fan region. This difference may be due to the noise in the image. This noise can be eliminated if Schlieren light received directly on a CCD camera. The results show that this analysis can be applied for both bright and dark regions of the Schlieren image with correcting the phase shift in the dark area. This optical technique has the advantages of optical measurements. This optical technique has all the advantages of optical measurements as does not disturb the flow and the high sensitivity to capture rapid variation.

Spatio-Temporal Variation of Groundwater Quality and Source Apportionment Using Multivariate Statistical Techniques for the Hutuo River Alluvial-Pluvial Fan, China

Groundwater quality deterioration has become an environmental problem of widespread concern. In this study, we used a water quality index (WQI) and multivariate statistical techniques to assess groundwater quality and to trace pollution sources in the Hutuo River alluvial-pluvial fan, China. Measurement data of 17 variables in 27 monitoring sites from three field surveys were obtained and pretreated. Results showed that there were 53.09% of NO3−, 18.52% of SO42− and 83.95% of total hardness (TH) in samples that exceeded the Grade III standard for groundwater quality in China (GB/T 14848-2017). Based on WQI results, sampling sites were divided into three types: high-polluted sites, medium-polluted sites and low-polluted sites. The spatial variation in groundwater quality revealed that concentrations of total dissolved solids (TDS), Cl−, TH and NO3− were the highest in high-polluted sites, followed by medium-polluted and low-polluted sites. The temporal variation in groundwater quality was controlled by the dilution of rainwater. A principal component analysis (PCA) revealed that the primary pollution sources of groundwater were domestic sewage, industrial sewage and water–rock interactions in the dry season. However, in the rainy and transition seasons, the main pollution sources shifted to domestic sewage and water–rock interactions, nonpoint pollution and industrial sewage. According to the absolute principal component scores-multivariate linear regression (APCS-MLR), most water quality parameters were primarily influenced by domestic sewage. Therefore, in order to prevent the continuous deterioration of groundwater quality, the discharge of domestic sewage in the Hutuo River alluvial-pluvial fan region should be controlled.

Laboratory investigations of the role of biofilms on stream‐bed surfaces in debris‐flow runout

AbstractDebris‐flow runout is a fascinating process to understand due to its implications for downstream alluvial fans. Based on the propagation‐deposition behaviors of the Dongyuege (DYG) debris flow, in Yunnan, the effect of biofilms on channel surfaces on debris‐flow runout is investigated in laboratory flumes with two different internal surfaces: surfaces are lined with granite slabs (Model I) and gravel (Model II), respectively.Our results show that biofilms can significantly reduce frictional resistance to flows. They increase flow velocities, slow down the deceleration of the snouts, prolong runout distances, and subsequently extend the areas covered with resulting deposits, thus greatly assisting the propagation of experimental debris flows. Slippery biofilms consisting mainly of diatoms and their extracellular mucus (ECM) reduce the contact friction between the flume‐beds and the overlying fluids, and greatly promote the propagation of tested flows.Well‐developed biofilms are found on the underwater channel surfaces of the DYG Creek. Acting as lubricating layers, they likely played a key role in the DYG debris‐flow runout. Most of the debris transported during the DYG event was deposited on overbanks, and the sediment that caused the disaster was transported to the populated fan region through the stream‐bed clad in the thick biofilms. Owing to their impacts on the development and width of the temporary debris dam breach, the stream‐bed covered with biofilms became a direct contributor to the debris‐flow hazard.Because of the ubiquitous presence of biofilms on mountain stream‐bed surfaces, the development of perennial streamflows can be viewed as an indicator of gully susceptibility to debris flows threatening creek fans. The underwater areas of pre‐event channel cross‐sections should be regarded as slip or low‐friction boundaries, and the parts above stream‐levels can be viewed as no‐slip boundaries. © 2019 John Wiley &amp; Sons, Ltd.

Assessment of sources and transformation of nitrate in the alluvial-pluvial fan region of north China using a multi-isotope approach

A multi-isotope approach and mixing model were combined to identify spatial and seasonal variations of sources, and their proportional contribution to nitrate in the Hutuo River alluvial-pluvial fan region. The results showed that the NO3− concentration was significantly higher in the Hutuo River valley plain (178.7 mg/L) region than that in the upper and central pluvial fans of the Hutuo River (82.1 mg/L and 71.0 mg/L, respectively) and in the river (17.0 mg/L). Different land use types had no significant effect on the groundwater nitrate concentration. Based on a multi-isotope approach, we confirmed that the main sources of groundwater nitrate in different land use areas were domestic sewage and manure, followed by soil nitrogen, ammonia fertilizer, nitrate fertilizer and rainwater, and there were no significant spatial or seasonal variations. Combining δ15N–NO3-, δ18O–NO3- and δ37Cl results can increase the accuracy of traceability. Nitrification could be the most important nitrogen migration and transformation process, and denitrification did not significantly affected the isotopic composition of the nitrate. The SIAR model outputs revealed that the main nitrate pollution sources in groundwater and river water were domestic sewage and manure, accounting for 55.9%–61.0% and 22.6% (dry season), 50.3%–60.4% and 34.1% (transition season), 42.7%–47.6% and 35.6% (wet season 2016) and 45.9%–46.7% and 38.4% (wet season 2017), respectively. This work suggests that the random discharge and disposal of domestic sewage and manure should be the first target for control in order to prevent further nitrate contamination of the water environment.

Plasma Wake Simulation for Charged Space Platforms: Fully Kinetic PIC Versus Hybrid PIC

A comparative study using both electrostatic hybrid particle-in-cell (PIC) and fully kinetic PIC simulations is carried out to study collisionless, mesothermal plasma flow over large, negatively charged plates. The surface potential considered covers plasma wakes under the “quasi-neutral,” the thin sheath, and the “thick sheath” regimes. It is shown that both approaches produce qualitatively similar plasma wake features. The hybrid-PIC approach is accurate in the sheath region around the plate and in the expansion fan region. The full-PIC simulations also confirm the presence of the embedded sheath in the wake generated by a charged plate. However, the hybrid-PIC model is quantitatively inaccurate in the deep wake region where the electrons are nonequilibrium. It is also found that, for high-voltage plates, the ratio of the ram side ion current collection to the backside one scales linearly with the logarithm of the surface potential.

Tracing nitrate pollution sources and transformations in the over-exploited groundwater region of north China using stable isotopes

Nitrate contamination in groundwater has become an environmental problem of widespread concern. In this study, we used environmental isotopes (δ15N-NO3− and δ18O-NO3−) and an isotope mixing model (SIAR) to identify the main sources of nitrate pollution, and factors controlling nitrate pollution, and to quantify the relative contributions of potential NO3− sources in an over-exploited groundwater region, north China. The results showed that human activities had dramatically increased the mean concentration of groundwater NO3− reaching 124.4 mg/L. In Hutuo River pluvial fan region, groundwater nitrate came from many kinds of pollution sources and the predominant sources were sewage and/or manure. Nitrification might be one of the most important nitrogen transformation processes and groundwater intensely exploited was a major inducing factor for the NO3− pollution. The highest contribution of groundwater NO3− was sewage and/or manure which the percent in the Hutuo River valley plain unit, upper pluvial fans of Hutuo River and central pluvial fans of Hutuo River was 54.9%, 55.0% and 61.8%, respectively, followed by soil N, NH4+ in fertilizer and rain, NO3− fertilizer, and NO3− in precipitation. We suggested that the local government must strengthen the sewage treatment for the collection of domestic sewage, and must prohibit over-exploitation of groundwater in order to prevent NO3− contamination of in groundwater.

A combined laser absorption and gas chromatography sampling diagnostic for speciation in a shock tube

The first implementation of a combined laser absorption diagnostic/gas chromatography (GC) sampling system for the measurement of combustion-relevant species in a conventional shock tube configuration is reported, with ethylene pyrolysis as an example application. A heated, endwall sampling system is used to extract a post-shock sample for GC analysis. Analysis of the gas sample yields a measurement of the ultimate mole fraction values of multiple species (currently ethylene, acetylene, hydrogen, and methane) at the end of the reflected shock test time. A 10.532-µm laser absorption diagnostic is simultaneously used to measure time-resolved ethylene. A method to accurately model sampled speciation results using published kinetic models is discussed. A method for extending laser measurements into the expansion fan region for direct comparison with sampled GC results has also been developed. The combined optical and sampled-gas measurement techniques were used to study ethylene pyrolysis (1.0% mole fraction ethylene/argon) at approximately 5 atm, over a range of temperatures (1200–2000 K). The ethylene mole fraction measurements obtained using both techniques show close agreement.

Investigation of Aeroacoustic Properties of Low-Pressure Axial Fans with Different Blade Stacking

Several blade-stacking strategies exist for low-pressure axial fans with potential benefits with respect to the aeroacoustic sound emission. In this study, the impact of such different blade-stacking strategies (including single-type and combined-skewed fan blades) on the fan characteristic curves, aerodynamic properties, and aeroacoustic properties was investigated. It was found that the fan aerodynamic and acoustic characteristic curves are strongly governed by the type of fan blade skew in the outer part of the fan blade. This was also observed for the flow-field on the suction side and on the pressure side. Sound pressure spectra and beamforming sound maps of the fans were further studied for one representative point in the typical fan operating range. The spectra showed similar tendencies as the fan characteristic curves, with spectra progressions being mainly dependent on the type of fan blade skew in the outer part of the fan blade. The sound maps revealed that, for the most part, sound sources are located in the outer fan region but that source characteristics may still be different for single-type and combined-skewed fans. These findings can be further used for reducing the sound emission of low-pressure axial fans with a focus on the fan blade shape in the outer part of the fan blade.

Facies analysis, depositional environments and paleoclimate of the Cretaceous Bima Formation in the Gongola Sub – Basin, Northern Benue Trough, NE Nigeria

Facies analysis of the Cretaceous Bima Formation in the Gongola Sub –basin of the Northern Benue Trough northeastern Nigeria indicated that the Lower Bima Member is composed of alluvial fan and braided river facies associations. The alluvial fan depositional environment dominantly consists of debris flow facies that commonly occur as matrix supported conglomerate. This facies is locally associated with grain supported conglomerate and mudstone facies, representing sieve channel and mud flow deposits respectively, and these deposits may account for the proximal alluvial fan region of the Lower Bima Member. The distal fan facies were represented by gravel-bed braided river system of probably Scot – type model. This grade into sandy braided river systems with well developed floodplains facies, forming probably at the lowermost portion of the alluvial fan depositional gradient, where it inter-fingers with basinal facies. In the Middle Bima Member, the facies architecture is dominantly suggestive of deep perennial sand-bed braided river system with thickly developed amalgamated trough crossbedded sandstone facies fining to mudstone. Couplets of shallow channels are also locally common, attesting to the varying topography of the basin. The Upper Bima Member is characterized by shallow perennial sand-bed braided river system composed of successive succession of planar and trough crossbedded sandstone facies associations, and shallower channels of the flashy ephemeral sheetflood sand – bed river systems defined by interbedded succession of small scale trough crossbedded sandstone facies and parallel laminated sandstone facies. The overall stacking pattern of the facies succession of the Bima Formation in the Gongola Sub – basin is generally thinning and fining upwards cycles, indicating scarp retreat and deposition in a relatively passive margin setting. Dominance of kaolinite in the clay mineral fraction of the Bima Formation points to predominance of humid sub – tropical to tropical climatic conditions. This favors pedogenic activities which are manifested in the several occurrences of paleosols. Pronounced periods of arid climatic conditions are also notable from the subordinate smectite mineralization. Chlorite mineralization at some localities is indicative of elevation of the provenance area, and this is synonymous with deposition of the Bima Formation, because of its syn – depositional tectonics. The absences of lacustrine shales in the syn – rift stratigraphic architecture of the Bima Formation indicates that the lower Cretaceous petroleum system that are common in the West and Central African Rift basins are generally barren in the Gongola Sub – basin of the Northern Benue Trough.

Groundwater quality assessment and pollution source apportionment in an intensely exploited region of northern China.

Deterioration in groundwater quality has attracted wide social interest in China. In this study, groundwater quality was monitored during December 2014 at 115 sites in the Hutuo River alluvial-pluvial fan region of northern China. Results showed that 21.7% of NO3- and 51.3% of total hardness samples exceeded grade III of the national quality standards for Chinese groundwater. In addition, results of gray relationship analysis (GRA) show that 64.3, 10.4, 21.7, and 3.6% of samples were within the I, II, IV, and V grades of groundwater in the Hutuo River region, respectively. The poor water quality in the study region is due to intense anthropogenic activities as well as aquifer vulnerability to contamination. Results of principal component analysis (PCA) revealed three major factors: (1) domestic wastewater and agricultural runoff pollution (anthropogenic activities), (2) water-rock interactions (natural processes), and (3) industrial wastewater pollution (anthropogenic activities). Using PCA and absolute principal component scores-multivariate linear regression (APCS-MLR), results show that domestic wastewater and agricultural runoff are the main sources of groundwater pollution in the Hutuo River alluvial-pluvial fan area. Thus, the most appropriate methods to prevent groundwater quality degradation are to improve capacities for wastewater treatment and to optimize fertilization strategies.

Response of Cenozoic turbidite system to tectonic activity and sea-level change off the Zambezi Delta

Submarine fans and turbidite systems are important and sensitive features located offshore from river deltas that archive tectonic events, regional climate, sea level variations and erosional process. Very little is known about the sedimentary structure of the 1800 km long and 400 km wide Mozambique Fan, which is fed by the Zambezi and spreads out into the Mozambique Channel. New multichannel seismic profiles in the Mozambique Basin reveal multiple feeder systems of the upper fan that have been active concurrently or consecutively since Late Cretaceous. We identify two buried, ancient turbidite systems off Mozambique in addition to the previously known Zambezi-Channel system and another hypothesized active system. The oldest part of the upper fan, located north of the present-day mouth of the Zambezi, was active from Late Cretaceous to Eocene times. Regional uplift caused an increased sediment flux that continued until Eocene times, allowing the fan to migrate southwards under the influence of bottom currents. Following the mid-Oligocene marine regression, the Beira High Channel-levee complex fed the Mozambique Fan from the southwest until Miocene times, reworking sediments from the shelf and continental slope into the distal abyssal fan. Since the Miocene, sediments have bypassed the shelf and upper fan region through the Zambezi Valley system directly into the Zambezi Channel. The morphology of the turbidite system off Mozambique is strongly linked to onshore tectonic events and the variations in sea level and sediment flux.

The Fan Region at 1.5 GHz – I. Polarized synchrotron emission extending beyond the Perseus Arm

The Fan Region is one of the dominant features in the polarized radio sky, long thought to be a local (distance < 500 pc) synchrotron feature. We present 1.3-1.8 GHz polarized radio continuum observations of the region from the Global Magneto-Ionic Medium Survey (GMIMS) and compare them to maps of Halpha and polarized radio continuum intensity from 0.408-353 GHz. The high-frequency (> 1 GHz) and low-frequency (< 600 MHz) emission have different morphologies, suggesting a different physical origin. Portions of the 1.5 GHz Fan Region emission are depolarized by about 30% by ionized gas structures in the Perseus Arm, indicating that this fraction of the emission originates >2 kpc away. We argue for the same conclusion based on the high polarization fraction at 1.5 GHz (about 40%). The Fan Region is offset with respect to the Galactic plane, covering -5{\deg} < b < +10{\deg}; we attribute this offset to the warp in the outer Galaxy. We discuss origins of the polarized emission, including the spiral Galactic magnetic field. This idea is a plausible contributing factor although no model to date readily reproduces all of the observations. We conclude that models of the Galactic magnetic field should account for the > 1 GHz emission from the Fan Region as a Galactic-scale, not purely local, feature.

An investigation into the noise generation of CPAP devices: Experimental and numerical study

Continuous positive airway pressure (CPAP) devices are popularly used for obstructive sleep apnoea (OSA) treatment. However, the noise level emission from these devices has been identified as a potential factor for patient’s discomfort and rejection. There is a need to obtain information on the noise characteristics and source locations in order to tackle the most serious noise source within these devices. A typical CPAP device was used for the investigation and its sound characteristics and sound power levels were determined. The noise generated from a centrifugal fan was also independently investigated to address its contribution to the overall noise of the device. Frequency analysis suggested that the noise generated from both the CPAP device and the fan is broadband in nature with discrete peaks containing rotational and non-rotational components. The broadband components were then studied in detail using numerical simulation approach. Computational aeroacoustics (CAA) method with hybrid approach was used to a three-dimensional (3-D) CPAP fluid model to predict the aerodynamic and aeroacoustics behaviours of the device. This showed a complicated flow structure involving flow separation, rotation, and vortices in several locations which resulted in high level of flow turbulence inside the device. The turbulent components were used to estimate the broadband noise level at source using the broadband noise source (BNS) models. It shows the most critical location is at the fan region and at the fan inlet.

Low-frequency polarization measurements of the diffuse radio emission of the galaxy

Polarization measurements of diffuse Galactic radio emission at 151.5, 198, 217, 237, and 290 MHz have been carried out in the direction of the North Celestial Pole, North Galactic Pole, one region of the North Polar Spur, minimum radio brightness of the Northern sky (l = 190°, b = 50°), and in the direction l = 147°, b = 9° in the so-called FAN region with enhanced polarization. The results obtained testify to the presence of low spatial frequencies in the angular distribution of the Stokes parameters Q and U of the diffuse Galactic synchrotron emission that are not detectable in interferometric observations. The spectra of the brightness temperature of the polarized component, rotation measures, and intrinsic polarization position angles of the radio emission in the studied regions are presented.

Active Channel Systems in the Middle Indus Fan: Results from High-Resolution Bathymetry Surveys

Multibeam swath bathymetry survey was carried out in the middle Indus fan region in the eastern Arabian Sea. Using high-resolution bathymetry data, major morphological features such as the Raman seamount and the Laxmi ridge have been mapped. This study also reveals the presence of sinuous channel systems, continuing towards the distal fan. Though there are several reports on the presence of channels in different regions of the Indus fan, we report here the presence of active channels to the east of the Laxmi ridge. The total length of all channels along the channel axis is about 915 km. The individual spreads of the channels vary from 189.8 to 1980.5 m. Most of the channels are shallow with the average depth measuring about 60 m. The longest channel is about 256.3 km long, 702 m wide and about 57 m deep. The channels observed are similar to the land-based fluvial channels. The channels identified are highly sinuous in nature, their meanders and cut-off meanders are similar to the characteristics of fluvial channels. In general, average channel course in the study area is more than twice the straight course.