Braiding Index Research Articles

Geomorphological characteristics of Gandak river between Sahibganj and confluence with Ganga river during 1989–2022

The Gandak River originates in Nepal and merges with the Ganga River in India. The Gandak River is experiencing significant geomorphological alterations due to climate change and anthropogenic causes. In this study, an attempt has done to examine river bank erosion & accretion, shifting of the river bank, sinuosity, and braiding index of the Gandak River between Sahibganj and the confluence with the Ganga River, covering a length of 92.4 km from 1989 to 2022 (33 years) using remote sensing and geospatial technologies. The delineation of the river bank line for different periods, along with the quantification of erosion and accretion of the river’s right and left banks, were analysed using GIS, including the sinuosity and braiding patterns. The overall sinuosity value ranged from 1.16 to 1.01 and did not follow any specific pattern in significant reaches. The sinuosity value was almost constant over the most d/s reach of 30.74 km. The braiding index of the River was found to be the maximum between Ismailpur and Baijalpur and the minimum value between Munja and Chakia in 2015 and 1995 respectively. This study revealed that the river is shifting to the right, and bank protection measures were needed. Finally, the proposed investigation revealed the braiding phenomenon, river shifting in the transverse direction, and shifting of the meander bend was primarily responsible for the erosion and accretion of the river banks. This study will benefit local government agencies, concerned authorities, and people residing along the banks of the Gandak River by providing insights into the river’s migration patterns. Further, this knowledge aids in better planning of riverbank protection measures and developing a navigation system.

Changes in the meander belt and channel pattern in the middle-low segment of the Cuarto river. Córdoba. Argentina

The Cuarto River is an important watercourse in the Córdoba Province, Argentina. Its middle-low segment crosses the eastern plains of this province, one of the most populated and (agricultural-livestock) productive regions of the country. In this segment, the channel and fluvial belt morphometric parameters exhibit notable changes downstream. Understanding the morphodynamics of the Cuarto River allows the characterization and definition of channel reach with tendencies towards migration, aggradation and overflow. In this way, it is possible to identify critical channel reaches, a fundamental aspect for effective planning. This work aims to characterize the downstream changes in the fluvial belt, meanders geometry, channel pattern and channel slope, along the middle-low segment of the Cuarto River and link these modifications with authigenic (sediment supply and transport regime) and allogenic controls. Five channel reaches (R1-R5) were selected according to geological-geomorphological criteria and different geometric parameters (channel width, channel slope, braided index, meander geometry, confinement degree) were determined for each of them. Empirical equations were used to establish relationships between these geometric parameters. Although most parameters showed a generally downward trend towards downstream reaches, marked changes were observed. Particularly, in the R1-R2 reaches, the fluvial belt widens and is unconfined, and the channel width and braided index also increases. The relationship between meander length/channel width (Lm/w) and radius of curvature/channel width (rc/w) obtained were within the ranges for free meanders (8–14) and high mobility (2–3), respectively. These parameter values are associated with alluvial channels and suggest limitations in transport and conditions for sedimentation. However, in R3, R4 and R5, the fluvial belt narrows and becomes confined, with high sinuosity, a reduction in the width of the channel and the braiding index. This pattern is expected for reaches characterized by predominance of transport and a tendency to a mixed or suspensive load. Moreover, both groups of reaches also exhibit an abrupt contrast in bedload size (from very coarse sand/gravel in R1 and R2 to fine/very fine sand in R3, R4, and R5). The similarity between the exponents of the predictive functions (Lm/w, rc/w, and Lm/rc) and those obtained for the Cuarto River, in addition to the satisfactory regression coefficients of the measured parameters suggest an acceptable balance between meander geometry and channel width regime of sediment transport. The middle-low reach of the Cuarto River shows notable changes, which can be linked to regional-scale allogenic factors such as morphostructures and lithology (R1-R2 with elevated morphostructure, R3-R4 are transitional reaches towards depressed plains, while R5 with subsidence environments). Nonetheless, the river demonstrates the capacity to regulate these factors at the reach level through authigenic processes. Thus the variability of channel width, channel slope, braiding index, meander geometry and degree of confinement are explained mainly by downstream changes in sediment supply and transport regime (authigenic controls) and secondarily by changes in regional slope and banks lithology (allogeneic controls).

Fluviomorphic trajectories for dryland ephemeral stream channels following extreme flash floods

AbstractEphemeral alluvial streams pose globally significant flood hazards to human habitation in drylands, but sparse data for these regions limit understanding of the character and impacts of extreme flooding. In this study, we document decadal changes in dryland ephemeral channel patterns at two sites in the lower Colorado River Basin (southwestern United States) that were ravaged by extraordinary flash floods in the 1970s: Bronco Creek, Arizona (1971), and Eldorado Canyon, Nevada (1974). We refer to these two floods as ‘fluviomorphic erasure events’, because they produced blank slates for the channels that were gradually moulded by more frequent but much smaller flood events. We studied georectified aerial photos that span ~60 years at each site to show that both study sites recovered to their pre‐flood condition after ~25 years. We employ channel network metrics: stream‐link area (SLA), geometric braiding index and junction‐node density. Each metric decreased during the short‐duration extreme flood erasure events. Subsequently, a fluviomorphic trajectory at a decadal tempo returned the channels to pre‐flood values. The SLA decreased at rates of 3.6%–4.1% per year in the decade following the floods. The extreme flood events decreased the pre‐flood geometric braiding index at the two sites by 56%–68%, and it took 15–24 years for this index to recover to pre‐flood values. In contrast, it took 30–35 years for the channels to recover to a uniform pre‐flood channel form, as indicated by the spatial distribution of bars and junction nodes. Our results document baseline examples of ephemeral stream channel evolution trajectories, as future climatic change will likely accelerate increases in the magnitudes and frequencies of extreme floods and geomorphic erasure events.

Evolution of the Pingluo Section of the Upper Yellow River over the Past 50 Years: Responses to Environmental Change and Human Activity

The instability of the river channels has increased in response to the combined effects of global warming and human activity. This instability threatens the lives and property of people who live along river courses. This study takes the Pingluo section of the upper Yellow River, which is ~28 km long and ~400 m wide, as its research focus. We studied 11 periods of Landsat remote sensing images from 1973 to 2023 and analyzed the evolutionary characteristics of the Pingluo section over the past 50 years. The channel morphology indices included the channel braiding index (BIT), the bar braiding index (BIB), the average area of the bar (Ab), and the width of the wet channel area (BW). The results showed that there was an overall shrinking trend in this section of the Yellow River; more particularly, fluctuations in indicators such as the river width and the braiding index highlighted an increasing–decreasing–increasing pattern of change. During the 1973–1986 period, the river showed a widening trend, with narrow anabranches cutting through the floodplain and both the river width and the braiding index increasing dramatically over a short period. Over the 1986–2018 period, the area of the wet channel continued to shrink to its lowest level for the past 50 years, the river’s branches were diverted and abandoned, and the channel tended to straighten out. Between 2018 and 2023, the river showed a slightly expanding trend. The evolution of the river channel appears to be related to regional human activity and climate change. For example, after the joint filling of the Longyangxia and Liujiaxia reservoirs in the upper reaches of the Pingluo section of the Yellow River in 1986, runoff and sediment load along this section decreased, flood events became less frequent, and the channel tended to contract. In addition, the increase in extreme precipitation events over the last five years has led to an increase in the magnitude and frequency of peak discharge values in the region, which is the main reason for the increase in the river braiding index and area.

Biogeomorphological floodplain dynamics along a degradation gradient of an Alpine river

AbstractChannel migration, furcation, and vegetation succession are characteristic processes of braided gravel rivers in Alpine regions. These are associated with a frequent turnover of large parts of the active floodplain. However, more than one century of river regulation has reduced or destroyed most of these ecosystem dynamics. More recently, there have been attempts to restore at least some sections of degraded rivers, while there is little monitoring of the biogeomorphological dynamics of such rivers. Thus, we did a four‐year analysis of four representative sections of the upper River Isar in Southern Germany differing in their degree of naturalness. Dynamics of channels, gravel bars, and vegetation were recorded by drone images, and braiding and gravel indices were calculated. When comparing the near‐natural, semi‐natural, degraded or restored sections, there was a gradient of decreasing channel migration, gravel bank expansion, and bank erosion due to a reduced turnover frequency. Biogeomorphological variation among years correlated with log peak discharge within the four sections. In addition, the cover and height growth of vegetation increased with river degradation, and channel migration was positively related to the braiding index. The total turnover of the active river corridor and of the vegetation were positively correlated with log peak discharge within the four sections. The floodplain dynamics of the restored section were improved compared to the degraded section but did not reach a near‐natural state. Thus, Alpine river sections with contrasting degrees of naturalness differ in terms of habitat turnover and vegetation succession, and these characteristics can only partially be restored by local measures.

Multiscaling behavior of braided channel networks: An alternative formulation of Taylor's law variate transformations.

Braided channel networks exhibit a complex interplay between spatial and temporal dynamics. Their behavior is characterized by both simple and multiscaling patterns, and the mechanisms underlying the stochastic processes associated with this dynamics remain incompletely understood. Leveraging Taylor's pioneering work [Nature (London) 189, 732 (1961)NATUAS0028-083610.1038/189732a0], which unveiled scaling relations in a plethora of natural phenomena through what is now known as the Taylor power law (TPL), we propose a physical interpretation of braided channel systems. This interpretation utilizes a specific class of transformation functions applied to the mean of fluvial geomorphic variables measured along cross sections, namely, the number of wet channels, the average width of wet channels, and the entropic braiding index. By analyzing remotely sensed data of the Brahmaputra-Jamuna River in Bangladesh we obtain valuable insight into the spatiotemporal scaling of these geomorphological variables and gather a deeper understanding of the complexity of braided channel systems. Finally, through a direct analysis employing the TPL in conjunction with a fixed-mass multifractal algorithm, we prove that braided channel networks exhibit a multiscaling behavior.

A new braiding index to assess river regulation effects in multi‐thread channels: Insights from a highly regulated Himalayan river

AbstractRiver regulation by dams and embankments drastically reduce/alter flow, which affects the natural channel pattern. Existing braiding indices have seldom incorporated the effects of diurnal flow variations caused by hydropeaking, leading to over/underestimation of the braiding intensity. These indices consider only the visible wet channels, ignoring the existence of dry channels that are activated only episodically during phases of water release from hydropower dams. We have extracted the dry channels (those that are periodically wet) coursing across the channel belt of the highly regulated River Tista from Landsat images between 1977 and 2014, using Normalized Difference Wetness Index values. These were combined with existing wet channel widths and numbers to formulate the Regulated Braiding Index (RBi) for characterizing channel braiding in the Tista's course over the Himalayan foothill plains. Overall, the widths and numbers of wet channels decreased by 63% and 25%, respectively, during the regulated years (2003 and 2014) as compared to pre‐dam years (1977 and 1995) due to the collective operation of 14 upstream dams/barrages (having cumulative ~89 million m3 reservoir capacity), whose operations reduced the braiding intensity (eliciting lower RBi values). Further, the number of high braiding reaches decreased by half while low braiding stretches rose by 10% in comparison to the pre‐dam period due to reduced/regulated flow. Comparative analysis of derived RBi values with three existing braiding indices revealed that RBi values consistently decreased near barrages, bridges, and within embankment‐confined reaches, unlike the other indices, thus providing a better framework for assessing expected river regulation effects.

Can Water-Detection Indices Be Reliable Proxies for Water Discharges in Mid-Sized Braided Rivers Using Coarse-Resolution Landsat Archives?

The use of water detection (WD) indices to infer daily discharge (Qd) has a great potential to enrich needed hydrological data for understanding fluvial processes driving the morphological changes of braided rivers. However, no consensus has been reached on which one stands out for use in mid-sized braided rivers. In this study, we compared the physical characteristics of three most commonly used WD indices, the Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), and Normalized Difference Moisture Index (NDMI), for two mid-sized braided reach segments in the Qinghai-Tibet Plateau, China, that have different morphological structures. Relying on the Google Earth Engine web interface, we calculated the total mean water width (WWt) based on the detected surface-water areas (As) and braiding index (BI), as well as the mean values (m) of these indices over about four decades at the braided corridor scale (cs) (mNDWIcs, mMNDWIcs, and mNDMIcs). We then examined different responses of these indices to water and non-water features and their best threshold values for characterizing channel structures. Our analyses demonstrated that (1) NDWI and MNDWI perform well for detecting braided channel structures with the threshold of zero; (2) WWt is generally better correlated to Qd in a linear style than WD indices do, particularly when calculated from MNDWI; and (3) among WD indices calculated at the braided corridor scale, mMNDWIcs shows a better relationship with Qd than mNDMIcs does. Finally, we provided mechanisms that may explain these differences in terms of photometric discrepancies in calculating WWt and WD indices and the impact of image resolution on their calculations.

Effects of vegetation distribution along river transects on the morphology of a gravel bed braided river

The interaction between vegetation, sediment, and water flow creates various fluvial landscapes. Hydrological conditions and flood disturbances, as well as the habitat preference of vegetation, regulate its spatial distribution. To describe the spatial distribution of vegetation cover, here, we focus on vegetation distributions along river transverse transects that define vertical and horizontal distances from water areas during low flow periods. As one of the most dynamic river types, braided rivers can be significantly influenced by vegetation encroachment. However, the effects of vegetation distributions along river transects on braided river morphology remain unknown. To study the potential influence of vegetation distribution along river transects, a depth-averaged, hydro-morphodynamic model was employed. Using the model, we investigated a medium-sized, braided river with a gravel bed affected by riparian vegetation. The following scenarios of vegetation transect distributions were examined: (1) vegetation established near or covering the low water channel, and (2) vegetation established on bar tops and kept at a distance from the low water channel. The model successfully reproduced a reduction in the braiding index for a vegetated braided river. Depending on the transect distribution scenarios employed, significantly different effects for river morphology were obtained. For example, compared to vegetation on bar tops, vegetation located near the low water channel played a more critical role for changing river morphology, redirecting water flow, and changing the statistical characteristics of the riverbed elevation distribution. Vegetation near the low water channel not only concentrated water flow to low water channels but also redirected flow to the high elevation area by reducing low water channel flow capacity. The revealed effects of the vegetation transect distribution on river morphology development helped to determine effective management protocols for reducing the negative impact of vegetation encroachment.

Large‐scale modelling of highly braided and laterally confined reach of a sand‐bed river

AbstractMorphological processes in sand‐bed braided rivers are highly complicated and dynamic, and it is challenging to fully comprehend and predict them quantitatively or even qualitatively. In this paper, we report the application of a physics‐based model with a single sediment fraction (D50 = 0.23 mm), based on field data, to simulate the morphodynamic processes of a large‐scale braided system in a wide valley of the middle Yarlung Tsangpo River in China. The model is capable of reproducing the evolution of large braided patterns at both microscopic and macroscopic scales, and simulating the formation of a high‐intensity braided reach from an initial lateral flat bed under lateral valley confinement. A narrow strip zone of braided corridor presents long‐term concentrated anabranches in the wide valley reach. Moreover, sensitivity analyses suggest that physics‐based modelling can simulate the multi‐thread river pattern even with relatively coarse grids and a large morphological acceleration factor. The model results show that active riverbed movement occurs and additional chutes are encouraged during flooding, while rising water level makes subchannels merge so that the statistical braiding index decreases. Conversely, only about 40% of the total channels are active in transporting sediment at low‐discharge stages, resulting in a local and slow bed scouring. The planimetric confinement of width variations and valley curvatures acts as a primary control on the local braided corridor and the forced bar assemblages. Width variations restrict the section‐average stream power for a given discharge event, while valley curvatures regulate velocity distribution through several control points. Moreover, the activities of riparian vegetation and sandstorm can interfere with the ability of rivers to braid in the corridor area, which requires much more attention in the follow‐up research.

Hydromorphological Information in Historical Maps of Switzerland: From Map Feature Definition to Ecological Metric Derivation

This article focuses on defining hydromorphological features to be extracted from historical maps by means of digital map processing techniques. The hydromorphological features, evolving through time, can be described quantitatively by the development and application of various ecological metrics to study the spatiotemporal change of the natural and built freshwater environment. With the goal to support future revitalization efforts, this article first reviews the theory on quantifying spatiotemporal change using landscape and ecological metrics, ranging from simple shape metrics (e.g., shoreline length) to more complex hydromorphological indexes (e.g., river braiding index). Second, the hydromorphological features themselves are important to consider in terms of data quality and uncertainty as they might inherit errors due to the low-quality maps, the extraction process, or due to poor definitions used during feature extraction efforts. Errors introduced by poorly defined features can be avoided by the use of a well-structured definition system. Thus, the article concludes in a new concept categorizing hydromorphological features and the changes they can undergo. The definition framework integrates novel perspectives for defining and evaluating features from the Siegfried and old Swiss national map, including key aspects from the theory.

CONCEPT OF CHANNEL PLANFORMS CHANGES ON POTENTIAL RIVER FLOODING

This study investigated the effect of channel planforms changes on potential river flooding in Kaduna state (River Kaduna as case study); with the aim to ascertain the effects of river channel planform on its potential flooding and put measures in place to advert the environmental menace. Topographic maps covering the entire course of the river and the characteristics of the river to be studied were obtained from the federal ministry of survey. The reliability of satellite images was verified by ground measurements using a 30m Surveyor’s tape on four bridges that cross River Kaduna. The measurements obtained were compared with correspondent measurements on the satellite image and found that the ground measurements and the measurements on both SPOT and Sentinel images were close. Three reaches (Meander 1, 2, 3; Straight reach 1, 2, 3 and Braided reach 1, 2, 3) were selected for this study. Variations measured along the river were changes in channel width, changes in sinuosity index, changes in braiding index channel lateral migration and changes in channel length from 1962 to 2017. The results showed a reduction in the channels width in all the reaches from average of 190m in 1962 to 74m in 2017; the sinuosity index was low in the duration considered (average of 1,15) while the braiding index value had a mean of 0.55. Channel migration also reduced from an average of 82m in 1962 to 53m in 2017 while the river reduced by 12% within this same period. The propensity of river flooding in the study area is high hence there is the need to carry out channel improvement, early warning system and desiltation of the river in order to eliminate the potential danger.

Quasi-equilibrium channel metamorphosis in planform of a subtropical river in India in post-dam period

A basic fluvio-dynamics process in the sediment-energy fluxes is channel meandering and braiding. The construction of dams and barrages has primarily altered the meandering and braiding patterns of the world's large rivers. To this end, the present study aims to analyze post-dam planform characteristics of the Damodar River, a subtropical river in India, based on the analysis of meander geometry, Mueller’s sinuosity index, braiding index, channel count index, and channel length index during the last 50 years (1970–2020) using topographical maps and satellite images. The study also intends to forecast channel meandering and braiding characteristics for 2030 and 2050 using an Artificial Neural Network (ANN) model. The study results show that between 1970 and 2020, the standard sinuosity index (SSI) showed a larger tendency to meander in the middle of the river than the upper and lower courses owing to hydraulic control, while the lower and upper courses were controlled by topographic factors. Similarly, channel braiding indices (BI*, BI, and Pt) exhibit swelling in the upper and middle courses followed by a gradual fall in the lower stretch. The building of dams, the presence of lineaments, faults, and other anthropogenic controls primarily regulate the physical planform characteristics of the river. Regarding allometry, the river's upper segments exhibit both positive and negative allometry in certain combinations, whereas the lower segments primarily exhibit negative allometry. The study demonstrates that over the past 50 years, overall channel meandering has slightly decreased while braiding has slightly increased over time, indicating a quasi-equilibrium channel metamorphosis. However, the prediction with higher accuracy (80–95 %) shows that the river meandering and braiding (BI* and BI) will increase in the short run (2030), and decrease in the long (2050). The study findings may be helpful for the various planners and stakeholders involved in the development of the river basin.

An Observation of the Changing Trends of a River Channel Pattern in Bangladesh Using Satellite Images

The shifting pattern of the Ganges-Padma River in Bangladesh is examined using satellite images. The meandering Ganges-Padma River has recently transformed into a braided river. Satellite imageries from 1973–2016 are used to compute the sinuosity ratio and braiding index (two measures that allow for the trend analysis). It turns out that both the sinuosity ratio and the braiding index went up with time, surpassing the cut-off for meandering. Overall, the braiding index variation exceeds the sinuosity variation.

Biogeomorphic recovery of a river reach affected by mining

AbstractEnvironmental changes are impacting river systems worldwide. These arise from factors such as flood magnitude–frequency changes, direct human management interventions, inadvertent human impacts on sediment supply and fluvial regimes and landscape‐scale changes in climate. Historical and active metal mining is significant in this regard. Here, we investigate morphodynamic changes within a reach of the River Ystwyth, Wales, since 1845. We analyse historical and contemporary information derived from maps, river flow records (1962–2021), metal analyses of sediment samples (1970s and 2021), ground geomorphological surveys (1970s and 1986–1987) and remotely sensed imagery (2001–2021) to investigate changes during a period of active metal mining followed by a century of post‐mining recovery. During the studied period, an initially meandering river was transformed into a braided one, subsequently reverting to a single sinuous channel. Sinuosity reduced from 1.31 in 1845 to 1.09 in 1982 before recovering to 1.39 in 2019. Inversely, the braiding index reduced from a maximum of 2.0 in 1987 to 1.5 in 2021. Evolution in planform was associated with a change from expansive bar formation and avulsion under braided conditions to lateral bar accretion and associated bank erosion along a sinuous single channel. The initial 19th‐century channel pattern and floodplain instability seems to have been related to mining sediment toxicity effects rather than a response to high sediment volumes, with recent recovery and channel style reversion being attributable to vegetation encroachment and biomass stabilization of the floodplain. Causal factors of recent recovery appear to be colonization by gorse (Ulex europeaus) in the absence of physical control measures and a reduction in grazing by the native rabbit population because of a disease‐induced decline in their numbers. These results highlight the importance of riparian vegetation in addition to sediment balance and hydrological processes in controlling fluvial responses to environmental changes.

The Entropic Braiding Index (eBI): A Robust Metric to Account for the Diversity of Channel Scales in Multi‐Thread Rivers

AbstractThe Braiding Index (BI), defined as the average count of intercepted channels per cross‐section, is a widely used metric for characterizing multi‐thread river systems. However, it does not account for the diversity of channels (e.g., in terms of water discharge) within different cross‐sections, omitting important information related to system complexity. Here we present a modification of BI, the Entropic Braiding Index (eBI), which augments the information content in BI by using Shannon Entropy to encode the diversity of channels in each cross section. eBI is interpreted as the number of “effective channels” per cross‐section, allowing a direct comparison with the traditional BI. We demonstrate the potential of the ratio BI/eBI to quantify channel disparity, differentiate types of multi‐thread systems (braided vs. anastomosed), and assess the effect of discharge variability, such as seasonal flooding, on river cross‐section stability.

Effect of Brick Field on Riverine Morpho-hydrological Environment: Study in Kopai River of South Bengal Plateau Fringe

Brick field is one of the important seasonal industrial activities in India but it has an antithetic impact on river. The majority of brick fields are of recent origin and situated along the bank of the lower catchment area. Nowadays, the rivers are adversely affected by increasing pollution and sedimentation, dumping of ashes, extraction of sand from the river bed and hinder the natural flow of the river. The present study is undertaken to assess the impact of the riparian brick field on geomorphic responses of hydraulic variables, planform change in different segments of Kopai River during 1990 to 2018 and spatial variation of river water quality. Location of riparian brick fields have been identified with the help of satellite imageries of different time periods (1990 to 2018), high-resolution Google Earth image and verified by GPS during field survey. The channel was divided into three segments to quantifying the geomorphic responses and changing planform indices. The study denotes that brick field activities lead to reduce the channel meander as well as decrease the sinuosity index and indicates a decreasing tendency of the braiding index as well as deteriorating the river health.

Assessment of Changes in Planform Morphology of the Upper Yamuna River Segment, India, Using Remote Sensing and GIS

ABSTRACT The current study explores the planform morphological changes that have occurred in the upper segment of the Yamuna River by using Landsat images from 1979 to 2019. The river segment was divided into 18 sections at equal spacing, viz., S1 to S18, and the centerline and bank line shifting, channel width, alterations in meander geometry and braiding characteristics in terms of sinuosity index (SI) and braiding index (BI) were evaluated. The results indicate a maximum centerline shifting eastward at section S-5 and westward at S17 during 1999, with respect to the base year of 1979. The average eastward and westward centerline shifting remained insignificant. The average west bank shifting ranged from 0.407 km to 0.892 km east and 0.440 km to 0.418 km west, indicating relatively higher west bank shifting towards east. The average east bank shifting ranged from 0.335 km to 0.505 km east and 0.344 km to 0.896 km west, indicating a narrowing of the bank width throughout the segment length. During the assessment period, the river segment exhibited sinuous characteristics and non-braided behavior. The outcomes of this study could be useful in predicting future trends in river shifting and developing sustainable land use planning strategies along floodplains.

Characterizing the trend of channel braiding of a tropical transboundary river using spatial growth component analysis and ARIMA model

Channel braiding is one of the fundamental fluvial processes in the context of sediment-energy nexus. The present study intends to simulate the channel braiding pattern of a tropical river (Jaldhaka River) on the Himalayan foreland plains. The grain size of the bed material in the Jaldhaka River decreases with distance from the mountain front, as does the surface gradient from the piedmont plains to the northern alluvial plains accompanied by the development of alluvial fans. Such assemblage results in multiple facets of hydro-geomorphic controls on channel planform dynamicity. This study is one of the pioneering attempts to characterize the spatial and temporal trend of channel braiding in any river running through the foreland region of the Sikkim-Bhutan Himalayas. The type of channel braiding is determined by the three indices – (1) Braiding Index (BI*), (2) Channel Count Index (BI), and (3) Channel Length Index (Pt), in cases where no gradual and uniform trend of development has been seen.The spatial allometric growth of the channel braiding and time series association using the ARIMA model was examined on the twenty stretches of the river. The results depict nonuniformity in planform development with distance downstream during a 30-year time span (1990–2020). The nature of the planform value distribution concerning all three applied indices has projected a polynomial trend where certain intermediate channel segments break the general trend of the braiding intensity with downstream distance. Since the downstream braiding intensity of the Jaldhaka River hasn't decreased either linearly or exponentially, we were unable to find any significant relationship of it with surface gradient. The nature and association of the channel braiding of the Jaldhaka River point towards the influence of local controls (e.g. river terracing on the upper part and faultline controls in the middle part) on channel planform dynamicity. The prediction of channel braiding for 2030 and 2050 coupled with the model fitted with RMSE, and BIC bears great significance in revealing the future bar growth which may be useful for the different planners and stakeholders concerned with the river basin development.

Assessment of the morphological trends and sediment dynamics in the Indus River, Pakistan

Abstract The Lower Indus reaches – Guddu and Sukkur – are among the most complicated areas in terms of reach migration. Both climate change and human activities in recent periods along with pond system operation accelerated riverine channel morphology. A GIS-based approach using multi-temporal Landsat images (1986–2020) was employed to characterize the morphometric parameters. Results showed that width of the study reaches varied from 2.1 to 12 km. The braiding index (BI) value for Guddu reach varied from 3.47 to 7.18, and BI value for Sukkur reach varied from 2.11 to 4.92. It is observed that no erosive activity of banks occurred for peak runoff value of <5,880 m3s−1. The sediment load during low flow (LF) period was estimated to be 0.715 million tons/day which comprised 77% fine sediment and 23% sand. The sediment load during high flood (HF) period was about 1.296 million tons/day. The median size (D50) of bed material during the HF period was 0.101–0.206 mm and during LF period was <0.0625 mm. The rough set theory (RST) showed that velocity, shear stress, slope, runoff, and sediment load factors are major contributors to the river shape changes. This study is a standpoint of planning flood recovery, riverine regulations, and navigation safety.