Outer Bank Research Articles

Glacial Isostatic Adjustment Modulates Lateral Migration Rate and Morphology of the Red River (North Dakota, USA and Manitoba, Canada)

AbstractThe lateral migration of a river meander is driven by erosion on the outer bank and deposition on the inner bank, both of which are affected by shear stress (and therefore channel slope) through complex morphodynamic feedbacks. To test the sensitivity of lateral migration to channel slope, we quantify slope change induced by glacial isostatic adjustment along the Red River (North Dakota, USA and Manitoba, Canada) and two of its tributaries over the past 8.5 ka. We demonstrate a statistically significant, positive relationship between normalized cutoff count, which we interpret as a proxy for channel lateral migration rate, and slope change. We interpret this relationship as the signature of slope change modulating the magnitude of shear stress on riverbanks, suggesting that slope changes that occur over thousands of years are recorded in river floodplain morphology.

Comparing turbulent flow and bank erosion with controlled experiments in a field-scale meandering channel

Abstract Bank erosion commonly occurs in alluvial rivers, shaping landscapes and riparian habitats and impacting water quality and infrastructure. Several models have been proposed that link shear stresses to bank erosion. However, data to test these hypotheses for characteristic geometries of meandering channels are sparse and technically challenging to acquire. Here we present results from a controlled experiment in a naturalistic channel to isolate the relationships between turbulent flow and nascent bank erosion. We ran the experiments at the Outdoor StreamLab (St Anthony Falls Laboratory, University of Minnesota) and gathered high-precision, contemporaneous measurements of the turbulent flow field and topography near a standardized, erodible bank at five locations along a single meander. The measurements show that the rate of bank erosion varied both along the channel and vertically and, local bank erosion was not correlated with any single hydrodynamic parameter. Upstream of the meander apex, erosion correlated with the near-bank time-averaged streamwise velocity magnitude while downstream of the apex, bank erosion correlated more strongly with near-bank turbulence parameters and depth. These results support field measurements that suggest that fluid shear contributions to outer bank erosion reflect multiple components of turbulent flow structure in river meanders.

Experimental study on velocity distribution and bed load transport in compound channels: Effect of the floodplain’s wall parallel with the meandering main channel

In this study, the effect of the floodplain’s parallel wall with a compound meandering main channel over the hydraulics flow has been analyzed experimentally. A constant sinuosity factor of 1.3 and relative flow depths of 0.3 to 0.55 were considered to illustrate the effect of the hydraulic parameters on the variations of the velocity components. Velocity components were measured by ADV velocimeter at seven cross sections with angles of zero, 30, and 60 degrees and mesh size of 2 cm × 2 cm. Furthermore, a laser meter measured the topographies of the sediment bed in the 33 cross-sections with an angle difference of 5 degrees to the bend apex. The results showed that in lower relative depths, due to vortexes and high turbulence intensity, the ability of flood damage will be more eminent. The CS04 section with the least longitudinal and transverse changes in the water level is the best position for hydraulic investigation of the meandering rivers. The left bank in sections CS03 to CS07 will be the place of deposit of sediment in nature with the formation of the stagnation area. The velocity of (Ud(fp-inner)) is 3 to 5 times higher than (Ud(fp-outer)). For this cause, the flow in the outer bank, unlike the inner bank, has a reduced effect on the flow velocity in the main channel. Increasing the relative depth, the ratio (Ud(mc)/Ud(T)) and (Ud(fp)/Ud(T)) decreased and increased, respectively. Therefore, the average velocity values in the main channel and the floodplains reached the average velocity of the whole section. The flow velocity in the main channel is always higher than in the floodplains, and the ratio (Ud(fp)/Ud(mc)) is less than one. The variation trend in the average values of bed shear stress, turbulence kinetic energy (TKE) and average kinetic energy (MKE) was decreased with increasing relative flow depth. Both factors of relative depth and Froude number will affect the location of the occurrence of the maximum values of velocity, bed shear stress, maximum depth hole and the peak of the sedimentary hill.

Water and heat exchange responses to flooding and local storm events in the hyporheic zone driven by a meandering bend

The hyporheic zone, i.e. the groundwater-surface water interface within riverine/riparian ecosystems, plays a key role in water transport, energy flow and biogeochemical cycling at watershed scales. Water and heat exchange are fundamental processes regulating biogeochemical cycles in the hyporheic zones. To improve the understanding of hyporheic flow and heat transport in meandering streams, high-resolution measurements of water level and temperature, combined with a 3-D coupled model of flow and heat transport in the hyporheic zone of a meandering bend, were carried out during a summer flood season. Results show the distinct spatio-temporal variations of hyporheic water and heat exchange. Flooding events (the incoming flood water generated by the upstream rainfall) and local rainstorm events (the storm or rainfall occurring over the local study area) are major drivers for the coupled processes. Incoming flooding from the upper stream increases the hyporheic water and heat exchange in the riverbed and inner bank leading to the longer intra-meander residence times, and warms the riverbed and riverbanks due to the post-rainfall thermal recovery. Local rainstorm event increases hyporheic water and heat exchange flux both laterally and vertically and cools down the riverbed and riverbanks. The water exchange and thermal regimes in the intra-meander seems more driven by the local exchange flows, while the counterparts in the outer bank are dominated by the regional groundwater flow. The temperatures in the inner banks are 1 to 3 °C higher than those in the outer banks, indicating the better hydrological connectivity between river water and groundwater in the intra-meander. The meander apex is a hot spot for hyporheic water and heat exchange. The results highlight the close coupling among river morphology, hyporheic flow, and thermal heterogeneity in a meander system.

Effect of sediment supply on the flow characteristics in a meandering channel

Meandering channels are common in natural rivers, especially in lowland alluvial plains. In this research, a meandering channel was designed in order to explore the effect of sediment supply on the flow characteristics. The water level, three-dimensional (3D) instantaneous velocity and riverbed elevation were measured using a digital wave altimeter, a 3D acoustic Doppler velocimeter and a 3D laser scanner, respectively, and the flow characteristics with and without sediment supply were compared. Under the same discharge, the transverse slope of the water surface in the case with sediment was larger than that without sediment and the change was steep; the change in the longitudinal slope of the water surface was small in the upper half bend and large in the lower half bend. By increasing the water discharge, the number of secondary flow vortices at the apex of the meandering channel increased. The trends of the mainstream lines with and without sediment supply were roughly opposite and the difference between them decreased with increasing discharge. The lateral and vertical turbulence intensities of the flow near the outer bank were larger in both cases (with and without sediment). In the case with sediment, the turbulent kinetic energy of the cross-section was larger near the bed and the water surface.

River bend sediment management using modified triangular vanes

ABSTRACT Triangular vanes (TVs) are among the flow pattern correction structures which have recently been considered environmentally friendly structures against river bend bank erosion. However, the scour around the structure’s tip may cause its failure. On the other hand, it has been shown that the use of slot in the bridge pier and bridge abutment is effective in reducing scour depth, hence in this study, the effect of four different positions of rectangular slot on TV: Case 1) near the TV’s tip, parallel to the vane’s chord and close to the bed; Case 2) near the outer bank, parallel to the vane’s chord and close to the water surface; Case 3) horizontally and near the bed and Case 4) vertically and near the outer bank is experimentally studied in a 90° mild bend flume. The maximum scour depth (ds), and the point bar height at the end of experiments were compared with the case of no slot (Case 0). The best performance in reducing ds was obtained for Case 1 and then Case 3 with 24% and 19% reduction compared to Case 0, respectively. Poor performance was found for Case 2.

Numerical Study on the Outer Bank Cell of Secondary Flow in a U-Shaped Open Channel

Due to the centrifugal force, a spiral flow is formed in a bend, presenting a rotating vortex in the vicinity of the inner bank and another rotating vortex in the opposite direction near the outer bank under certain hydraulic conditions, which have a significant effect on bank erosion processes. The renormalization group k-ε turbulence model was employed to simulate the flows in a U-shaped open channel with various Froude number (Fr). The water level, vertical velocity and secondary flow structure were analysed. The outer bank cell (OBC) has a strong dependence on the Fr and the intensity of the OBC (QOBC) firstly increases and then decreases along the channel. The maximum QOBC gradually increases and the position of the maximum value first moves downstream and then upstream with the increasing Fr. At the apex of the bend, the nondimensionalize intensity of the OBC first decreases and then increases with the increasing Fr.

Experimental and Numerical Study on Flow Control Using 3-Array Submerged Vane in Laboratory Channel Bend

Regulation structures such as submerged vane are needed to reduce and eliminate environmental damage due to increased flooding in rivers. In particular, scours on the outer bank due to increased flow velocities cause the river bed to change and deteriorate. In this study, the effect on flow velocities was investigated experimentally by using 3-array submerged vane structures in areas close to the outer bank. The experimental vane results were performed in the open channel setup. The Computational Fluid Dynamics (CFD) results obtained with the numerical model were also verified and compared with experimental results. It has been observed that the CFD model gives results close to the real experimental results. The standard-based k-ε model was used as the turbulence model. In the outer meander, the 3-array submerged vane with a 3-vane structure was found to affect the flow velocity by 16–27% in the region behind the vane. The flow velocities were investigated along with depth using the CFD and found that the mean velocity was reduced by 14–21% along the depth. It is also recommended that submerged vane structures can be applied as an effective method in reducing flow velocities and directing flows.

Influences of Momentum Ratio on Transverse Dispersion for Intermediate-Field Mixing Downstream of Channel Confluence

This study aims to analyze the influences of momentum ratio (Mr) and confluence angle (α) on the transverse dispersion in an urban scale confluence channel from the numerical simulation results using the Environmental Fluid Dynamics Code model. By changing the momentum flux and confluence angle from the simulation results, the analysis focused on the relations between the vertical variations of transverse velocity and transverse dispersion. The high momentum tributary aligned the mixing interface toward the outer bank and created a strong helical motion, which transported the contaminated water along the channel bed and inflows into the recirculation zone. The high momentum ratio induced the large vertical shear in transverse velocity with a strong helical motion and increased the transverse dispersion. However, the helical motion persistence rapidly decreased as the flow reached downstream and led to a decrease in the transverse dispersion for the large confluence angle. Thus, the transverse dispersion coefficient increased with a high momentum ratio and low confluence angle, and the dimensionless transverse dispersion coefficient was in the range of 0.39-0.67, which is observed in meandering channels, for Mr > 1 and α = 45°.

Patterns in the plankton – Spatial distribution and long-term variability of copepods on the Agulhas Bank

Copepods dominate the zooplankton community on the broad Agulhas Bank off southern Africa, where they provide an important food resource for pelagic fish and other biota. Previous studies have shown the dominant copepod Calanus agulhensis, which may comprise up to 80% of copepod biomass, to be strongly associated with the productive cold ridge of upwelled water on the central (CAB) and eastern (EAB) Agulhas Bank. However, there is little information available on other copepod taxa, and whether the Agulhas Bank community has changed over time in response to environmental variability or other ecosystem changes, such as the recent eastward shift in pelagic fish distribution. We use in situ temperature, chlorophyll a (chl a), and zooplankton data collected annually in late spring to explore spatio-temporal variability in copepod biomass and species composition on the Agulhas Bank over a 24-year period, from 1988 to 2011. Functional traits were used to interpret the observed patterns. Total copepod abundance and biomass were concentrated on the outer central and eastern shelf (>100 m), coincident with the region of elevated chl a at 30 m, and largely downstream from cooler subsurface water linked to the cold ridge and coastal upwelling. Current and cruise-feeding herbivores C. agulhensis and the smaller Para- and Clausocalanidae collectively accounted for 73% and 54% of total copepod biomass and abundance respectively, driving the main patterns for total biomass. C. agulhensis copepodites showed an ontogenetic shift in distribution with distance offshore and downstream from the cold ridge, and accumulation of older stages near the southern tip of the bank. The upwelling specialist Calanoides natalis was closely associated with shelf-edge upwelling, particularly near the Agulhas Bight, but was low in biomass compared to the Benguela upwelling system. The current/cruise-feeding detritivores Metridia lucens and the Oncaeidae were largely associated with the western sector of the bank but showed different niche preferences. M. lucens inhabited the chl-rich outer bank of the western Agulhas Bank (WAB), likely a continuation of the southern Benguela upwelling system community, while oncaeid biomass was associated with deeper thermoclines across the WAB and western part of the CAB that often feature accumulations of the gelatinous zooplankton they feed on. Centropages spp. and the Oithonidae, mainly omnivorous ambush feeders, were associated with the inner to mid-shelf region of the WAB and CAB, away from the main influence of the Agulhas Current. Centropages biomass aligned well with elevated chl a on the inner WAB, likely an extension of the Benguela community (C. brachiatus), and with the cold ridge over the inner CAB shelf, matching earlier patterns linked to C. chierchiae. Oithonidae were widespread but low in biomass, and scarce over the Agulhas Current-influenced outer shelf, suggesting a suboptimal environment overall for this group compared to the cooler Benguela upwelling region. Current-feeding and omnivorous Pleuromamma spp., known to be deep vertical migrators, were concentrated beyond the WAB shelf edge. Total copepod biomass showed a significant decline over the entire Agulhas Bank during the 24-year time series, as did all stages of C. agulhensis, including large nauplii, and the small calanoids (Paracalanidae and Clausocalanidae). No long-term trends were observed for the other copepod taxa. We found no trends in temperature, but a significant but weak (1.5% yr−1) increase in chl a at 30 m. Although there was no obvious shift in copepod biomass in response to the eastward shift in pelagic fish in ca. 1996, there were significant negative relationships between copepod biomass (for total copepods and C. agulhensis) and pelagic fish biomass (total, anchovy and redeye) from 1988 to 2011, with significantly lower copepod biomass after 1998 compared to before. This suggests predation pressure has an important top-down influence on copepod biomass on the Agulhas Bank. Bottom-up forcing from environmental drivers cannot be ruled out, however, despite ambiguous results from in situ and remote data series, and long-term warming due to climate change is expected to negatively impact ecosystem productivity at the large scale.

Experimental investigation of flow pattern over a fully developed bed at a 60° river confluence in large floods

River confluences have a complex flow and sedimentation pattern that have vital influences on the hydraulic and bed morphology of river reach and the surrounding area. Confluences can be observed in waterways with various situations such as live bed conditions. This condition is a hydro-morphological situation with a high densimetric Froude number, i.e., bed load transport is supplied from upstream. According to the literature review, most of the experimental studies investigate the flow pattern on the flatbed and not on the developed riverbed, or/and in the low densimetric Froude number, or/and without supplying the sediment from upstream. Therefore, in the present study for the quantification of the flow pattern under these conditions, each developed bed was fixed with the cement blanket method in the laboratory. Then, the 3D velocity was measured at specific points at the confluence. The current study was designed to understand the flow pattern corresponding to the river bed behavior in the case of large floods. It is expected that the morphological features downstream of the confluence have a different pattern than the ones in the condition described in other literature. Thus, this paper describes briefly what are the different bed features and investigates the corresponding flow pattern. The results of the flow pattern on the developed bed show that all zones at the river confluence can be observed except the point bar due to the approximate equality of the mean longitudinal velocity of the separation zone and the main channel upstream of the confluence. Moreover, results show that by increasing the bedload ratio (sediment discharge to water discharge of the main channel of upstream of the confluence) from 0 to 3 × 10−4, flow deflection to the outer bank of the channel decreased down to 45%, the stagnation equivalent area decreased down to 2.5 times, and bed shear stress decreased down to 40%. Hence, the momentum of lateral flow decreased with increasing bedload. Besides, the recovery zone occurred at a longer distance after the confluence compared to the case without bedload. Hence, the location of the maximum velocity zone, vortices, and secondary flows changed downstream of the confluence, by changing the bed load value.

Local scour at a bridge abutment along a curved channel

Few studies have focused on abutments located on curved channels; previous studies have typically focused on straight channels. The present study experimentally examined the local scour that occurs around abutments of different lengths placed on inner and outer banks along a curved channel under clear-water scour flow conditions. The local scour around an abutment in a curved channel is a function of the upstream Froude number, flow intensity, the angle of the bend curvature and the ratios of abutment length to flow depth, abutment length to abutment width and abutment length to channel width. The maximum scour depth around the abutments placed on the outer bank was 1.45 times the scour depth on the inner bank. An empirical equation was developed containing all the dimensional parameters for equilibrium scour depth. The average percentage error of the proposed equation was 2%.

Quantitative analysis of crevasse-splay systems from modern fluvial settings

ABSTRACTAlthough crevasse splays are a common constituent of many fluvial and fluvio-deltaic systems, they remain less well understood than the channel deposits in those settings, especially with respect to controls on their occurrence, distribution, and geometry. The current study aims to redress this balance and investigate controls on 1) splay formation and occurrence and 2) splay size and geometry. The study has used Google Earth-based satellite imagery to examine crevasse-splay deposits from eight modern fluvial systems. A total of 1556 crevasse splays were identified using imagery from 1984 to 2020. Most of the splays (c. 70%) occur on the outer sinuous river bank with offtake angles ranging from 10° to 140° (mean 75°) to the channel flow direction. Three different types of splays have been identified: i) single crevasse splays, ii) laterally amalgamated crevasse splays, and iii) crevasse-splay complexes. The areal extent of splay bodies varies widely and ranges from less than 1 km2 up to 221 km2. The single crevasse splays are the primary and smallest form of splay, with an average area of 0.61 km2. Compensational stacking or progradation significantly increase the splay area and form laterally amalgamated splays and splay complexes, respectively. The average areal extent of laterally amalgamated splays is 1.33 km2, and of splay complexes, 39 km2.The climate, discharge, floodplain morphology, vegetation, trunk channel slope, sinuosity, and sediment load primarily control the occurrence, geometry, and dimensions of crevasse splays. Results demonstrate that sparse or no floodplain vegetation favors the formation of elongated tongue-shaped crevasse splays while densely vegetated floodplains produce more lobate splays. The highest splay frequency occurs in systems where the river experiences sudden high magnitude variation in discharge, has a low cross-sectional area, and noncohesive bank materials. Larger splay size is correlated with lower river slope angles and higher sinuosity, discharge, and floodplain relief. Channel size has little influence on the extent of splays. This work suggests that autogenic factors such as trunk-channel slope and sinuosity are more influential in arid–semiarid settings while allogenic factors such as discharge are important in temperate–equatorial settings.

Paleoenvironmental reconstruction, paleoecology and sequence stratigraphy of some Nummulites buildups in Egypt

The present study deals with microfacies analysis, paleoecology and sequence stratigraphy of the Lower–Middle Eocene rocks in central Nile Valley and west-central Sinai. Four rock units were marked (Minia, Darat, Samalut and Maghagha formations). Eight facies belts were interpreted including lagoon, back bank, main bank, fore bank and open marine outer bank facies and deposited on a gently dipping platform ramp. This ramp might be further divided to three main faunal associations depending on the depth of the water and associated fauna. Four major depositional sequences (DS1–DS4), reflecting third-order cycles and separated by two prominent sequence boundaries (SB1 and SB2) were marked. The record of these sequences reflects the changes in eustatic sea level plus the regional tectonism in the area. Every sequence includes facies associations, which constitute lowstand and/or transgressive and highstand systems tracts. Based on faunal elements and facies analysis, the water salinity, water temperature, nutrients, substrate, water depth and hydrodynamic behavior were discussed. The fine-grain size of the deposits, the loss of good connectedness and the occluding of the Nummulite tests by other minerals could give rise to low reservoir potential. The sedimentation was affected by the tectonic activity of the Syrian orogeny. Moreover, both external and internal mechanisms have controlled the carbonate sedimentation, basin construction and sequence bounding surfaces.

Mean flow, secondary currents and bed shear stress at a 180-degree laboratory bend with and without enhanced permeable groins as an Eco-friendly river structure

River restoration aims to apply environmentally-friendly structures for bank protection in meandering rivers to restore their natural habitat. Enhanced Permeable Groin (EPG) is a novel river restoration technique that can improve the fish habitat environment in a river system by creating a series of eco-friendly scour pools. This study reports the results of two groups of 3D velocity measurements in a 180-degree channel bend in cases with and without an EPG for clear water conditions to characterize the mechanisms leading to the primary stages of the scouring phenomenon. The analysis revealed that the presence of an EPG amplified the velocity magnitude in the regions near the tip of the vane and increased its value in the middle of the channel 1.13 times the bend without the structure. In addition, the comparison showed that the EPG reduced the velocity magnitude in the recirculation zone by an average of 38%. Secondary currents including main and outer bank cells were observed in the case without the structure. The presence of the EPG in the flow field effectively increased the outer-bank cell strength by 11 times compared to that without the structure. The low-value contours of the bed shear stresses were observed in the zone downstream of the structure for a distance of 6 times the effective length of the structure. Based on the results of this study, the generation of a recirculation zone with low-velocity and shear stress values can provide suitable conditions for aquatic habitats, deep-bodied fish assemblages, aquatic vegetation, shrub roots, and tree roots along the outer bank.

"국내 충적하천에서 측방 이동에 대한 계량적 분석 - 내성천 고평 지점을 사례로 -"

In this study the lateral migration of an alluvial river, which occurred between 2015 and 2021 at the Gopyeong site of the Naeseong Stream was quantitatively analyzed and the relationship between the hydraulic characteristics of the floods and bank erosion was examined. Bank erosion began in the upstream part of the study reach and then was concentrated on the downstream part beyond the bend apex, showing lateral and downstream migration. Average annual migration rate is 5.6 m/yr. Annual change of the crosssection shows that the lateral migration is accompanied by the retreat of the outer bank, formation of a pointbar at the inner bank together with the incision of the low water channel bed that appeared throughout the river. Volumetric sediment relocation brought forth by these processes was evaluated. Bank erosion is controlled mainly with floods, and eroded area is proportional to the duration of inundation. The results of this study imply that a series of drone/aerial images are useful for the quantitative analysis on the lateral migration of alluvial rivers.

Mean flow characteristics in a flat and eroded bed curved channel

The mean flow characteristics in a curved channel are really different from those in a straight channel. The main cause is the existence of secondary flow within the flow in the curved channel. This paper will discuss the differences in mean flow characteristics due to changes in the bed topography in the curved channel. Acoustic Doppler Velocimetry (ADV) measurements have helped to analyse characteristics of the mean flow on flat and eroded beds in a 180° curved channel. Sand (mean diameter d 50 = 0.001 m and specific gravity Gs = 2.65) was selected as the bed material. The condition of flow in the approach section was steady and uniform with 0.159 m depth. One of the mean flow characteristics in the curved channel is the free surface superelevation due to the presence of centrifugal force. The second is the circular motion toward the inner-bank region at the lower layer and toward the upper layer outer-bank region. The cause of the circulation is the difference in centrifugal forces between the two layers. The magnitude of velocity near the bed surface is more significant than the flow near the water surface. This causes erosion in the outer bank region and deposition in the inner bank region. In general, tangential velocity vθ in flat bed is greater than its tangential velocity in eroded bed. The maximum velocity path in a flat and eroded bed of the curved channel resembles a sinusoidal curve, where the minimum value is located at 90° and 120° of the curve.

Experimental Studies on the Influence of Negatively Buoyant Jets on Flow Distribution in a 135-Degree Open Channel Bend

The present paper aims to investigate the evolution of velocity fields as well as secondary flows in an open channel bend under the influence of negatively buoyant jets. A 135-degree open channel bend was used for experiments, and the jet nozzle was located along the outer bank in the straight section upstream of the bend. Efforts were made to specify the flow structures with high precision measurements of three-dimensional velocities by means of a three-dimensional PIV (Particle Image Velocimetry) technology. The experimental results show that the jets comparatively affect the flow structure at the beginning and exit of the flow in a bend. Although the jets had little effect on the maximum streamwise velocity, complex secondary flow patterns and properties were found to be influenced due to the occurrence of the negatively buoyant jets in the bend.

Evolution of outer bank cell in open-channel bends

Evolution of outer bank cell in open-channel bends

Turbulence structure in a very sharp thermally stratified open-channel meander

Direct numerical simulation (DNS) results for turbulent open-channel flow through an idealized sine-generated meander with and without an internal heat source that models radiative heating from above are used to analyze the effect of a very sharp meander configuration and thermal stratification on the turbulence structure in the channel with friction Reynolds number Reτ=200. Spatial distributions of temperature, mean velocities, vorticity, mean-flow kinetic energy, and turbulent kinetic energy (TKE) are presented. In both cases, the cross-sectional motion is characterized by three circulation cells: a center-region cell and two weaker outer bank and inner bank cells. However, there is also a small cell observed near the corner of the channel bed inner bank at the channel outlet and the channel bed outer bank at the channel inlet. The tri-cellular cross-stream motions control the distributions of temperature and kinetic energy. In the stratified case, two separated shear layers (SSLs) are found: the first one is formed before the bend apex, and the second one is observed in the wake after the bend apex. In the neutral case, only the first SSL is observed. Turbulent amplification can be seen in both cases; however, in the stratified case, the second SSL stretches out to the channel outlet and is introduced back to the channel inlet by an anti-symmetric periodic boundary condition and then follows the outer bank line. The two SSLs converge in the region before the bend apex and amplify the turbulence more strongly there than in the neutral case. The turbulence kinetic energy budget terms for the stratified case are analyzed to determine the characteristics of production, dissipation and transport of TKE in thermally stratified meandering flow.