Sinuosity Ratio Research Articles

Internal Architectural Patterns of Bar Fingers Within Digitate Shallow-Water Delta: Insights from the Shallow Core, GPR and Delft3D Simulation Data of the Ganjiang Delta, China

Abstract Digitate shallow-water deltas are commonly found in modern lakes and bays, as well as within cratonic petroliferous basins. They develop one or multiple sinuous finger-like sands (i.e., bar fingers), including high-RSI (sinuosity ratio of distributary channel and bar finger ≥1) and low-RSI (RSI < 1) types. Bar fingers consist of four types of subenvironments, that is, distributary channels, point bars, mouth bars, and levees. However, the internal architecture within the above subenvironments is still unclear. This paper documents the internal architecture of a digitate delta based on the integration of shallow-core and ground-penetrating radar data from the Ganjiang Delta, China, coupled with Delft3D simulations. Our results show that multiple convex-up muddy-silty accretion beds are developed in mouth bars, which top lap the side of the distributary channels or point bars and down lap the bottom of the mouth bar. The accretion beds have low dip angles (<2°), which is slightly higher for the upper accretion beds. Point bars, unique to the high-RSI bar finger, develop multiple inclined silty drapes, which top lap the top of the point bar. The cohesive levee and backwater effect impede the migration of the distributary channel, resulting in silty drapes with high-dip angles (can be >10°) compared with those in the supplying river. This dip angle exhibits a negative relationship with downstream distance and a positive exponential relationship with lateral migration distance. Silty drapes become dense along the migration direction of the distributary channel. The levee develops multiple horizontal muddy accretion beds. The high-RSI bar finger develops a large number (>3) of accretion beds in mouth bars with high dip angles, and a large number of accretion beds in thick levees, compared with the low-RSI bar finger. The results of this paper provide insights into the prediction and development of cratonic digitate shallow-water delta reservoirs.

Modelling the Impact of Climate Change on the Flow Regime and Channel Planform Evolution of the Lower Drava River

Climate change is expected to have a significant impact on changing the flow regime of the lower Drava River. Four flume experiments were run to see how stabilized, increased and decreased flow and the occurrence of a series of floods affect channel planform evolution. Constant discharge produced alternate bars that subsequently merged into bigger bedforms, bedform migration, and a higher sinuosity of the channel. While merging and migration of bedforms may happen in the lower reaches of Drava, its sinuosity is unchanged due to river regulation. Reduced flow initiated transition from a braided to incised single-thread planform, with the formation of dormant channels. Drava already has a single-thread planform (because of dikes) and, in cases of flow reduction, will have the remnant of inactive channels. Increased discharge showed greater erosion and reworking of channel banks, a decrease of sinuosity ratio and active high bluff zones. On Drava sinuosity ratio is more difficult to change because of levees, but erosion, reworking of banks, and increased high bluff risks are possible. Floods simulation generated the construction of an anabranching planform alongside the incised main channel with terraces along banks (active during floods), bars, alluvial islands, and side channels (active during low flows). On the lower Drava River, this situation correlates with past floods.

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.

Morphological Characteristics and Hydrological Connectivity Evaluation of Tidal Creeks in Coastal Wetlands

Tidal creeks play a critical role in delivering water, suspended sediments, and nutrients to coastal wetlands, so it is important to understand the characteristics of the tidal creek system to guide the development and sustainable utilization of coastal wetlands. Using the coastal wetlands of the Liao River Estuary (LRE) as a study area, this study accurately divided the tidal flat based on the principle of tidal correction, extracted the linear features of tidal creeks using high-resolution remote sensing (RS) data, and then classified the tidal creeks on a tidal flat using the tidal creek ordering algorithm. Our study aimed to quantify the morphological characteristics of tidal creeks and qualitatively evaluate the parameters of the tidal creek network in the study area. The study results show obvious spatial heterogeneity in the order and the average length of tidal creeks in the coastal wetlands of the LRE. With the increase in the order of tidal creeks, the average length of tidal creeks increased exponentially and the number of tidal creeks decreased exponentially in the study area. The total density of tidal creeks was related to the beach surface elevation gradient, and the density and frequency of tidal creeks reduced substantially with an increase in the order of tidal creeks. The sinuosity ratio of tidal creeks declined sharply with a fall in the beach surface elevation gradient. The average bifurcation ratio of tidal creeks in the upper intertidal zone was higher than that in other zones, indicating that the tidal creeks in the upper intertidal zone were erratic. In addition, the hydrological connectivity of the tidal creek network in the upper intertidal zone and the development of the tidal creek system in the supratidal zone were the highest in the LRE. The study results help understand the spatial variations in tidal creek morphology under the influence of tidal hydrodynamics.

Geomorphologic Evolution and Morphometric Analysis of the Upper Basin (Güzelsu) of the Engil River (Van)

The study area is located in the Eastern Anatolian Plateau found in the Alpine-Himalayan fold mountain belt. The Engil River Upper Basin (Güzelsu) is within the Lake Van Closed Basin, the largest soda lake in this belt in terms of volume and area. This study aims to investigate the geomorphologic evolution of the Güzelsu Basin and support this development with morphometric analysis. With this aim, a Digital Elevation Model (DEM) was created with the aim of quantifying and evaluating field observations and findings, 22 subdrainage areas located in the basin was determined by the DEM. The indices of Hypsometric integral, Hypsometric curve, Basin shape, Elongation ratio, Drainage basin asymmetry, Mountain front sinuosity ratio, Valley width-height ratio were applied to these drainage areas which were formed depending on internal and external processes. When the geomorphological and sedimentological findings in the field studies were evaluated with the applied index results, it was revealed that the basin geomorphology was formed under the influence of tectonism, climate and fluvial processes.

Changes in the hydrological regime and channel morphology as the effects of dams and bridges in the Barakar River, India

The anthropogenic activities affect the river channel as well as the whole system in different magnitudes and dimensions. Barakar River, the main tributary to the Damodar River in eastern India, is modified by several engineering structures. Hydrological parameters, such as monthly discharge, peak flow discharge and geomorphological factors, such as gradient, width–depth ratio, grain size, braid–channel ratio, sinuosity ratio, riffle-pool sequence, and stream power are taken into consideration to highlight the significant alterations of the river due to dam and bridge construction. The alterations are assessed with the help of hydrological data, satellite images, and digital elevation data along with field survey. The downstream section of the dams, the river is characterised by high braiding, sinuous, total and unit stream power along with the presence of a box-shaped bedrock channel, high gradient, bed coarsening and armouring due to the release of high-velocity sediment-free ‘hungry water’. In the upstream reach, the grain size decreases towards the dam, and it increases suddenly with poor sorting at the immediate downstream regime of the dam. The effects of bridges on the Barakar river morphology include an increase of gradient, width and depth of the river channel at the downstream of the bridges. The construction of bridges influences riffle-pool sequences. Thereby, the pool depth spacing is greater than the riffle crest spacing. However, the integration of natural as well as human-induced factors can be the best approach to understand the anthropogenic alteration of the river. Moreover, construction of some check dams at the upper section of the tributaries of the Barakar River can be very effective for morphological stability.

Parameterizing the Yellow River Delta tidal creek morphology using automated extraction from remote sensing images

The tidal creek is an important part of the intertidal zone, which maintains the balance between depositional processes and a given hydrodynamic environment. Much can be inferred about the development and evolution of a tidal creek by examining its morphometry characteristics; this information can also provide scientific decision support for the development and utilization of coastal tidal flats. In this study, we propose a complete system of large-scale tidal creek morphometry characteristic extraction algorithms. This system improved the intelligence of the node classification and the accuracy of the grading, as well as mitigates the interference of island-shaped tidal creeks in the automatic iterative classification process. And this system solves the problem of low post-processing efficiency due to the existence of a large number of discontinuous tidal creek arcs, and greatly reduces the error in the calculation of morphology characteristics. After accuracy verification, using this algorithm, the classification accuracy of tidal creek nodes is 92.22%, and the order and flow direction information of nearly a thousand tidal creeks can be quickly and automatically defined, and the classification is error-free. The whole process is fully automatic, and it is better than previous algorithms in terms of efficiency and accuracy. It's greatly improved. After quantifying tidal creek morphometry characteristics such as the order, number, length, sinuosity ratio, bifurcation rate, and density, we identified the factors that affect the development of the tidal creek network with respect to its seawater intrusion and vegetation distribution. Our conclusions are as follows: (1) The order and number of the tidal creeks increase from north to south and from west to east. And the average length of the tidal creek increases with the order of the tidal creek. The sinuosity ratio of the tidal creek on the land side is greater than that on the sea side. The density of the order 4 tidal creek system is greater than other tidal creek systems. The differences in these characteristics are mainly related to vegetation distribution and seawater erosion. (2) Seawater erosion promotes rapid changes in the tidal creek sinuosity ratio, bifurcation rate, and density. However, due to the shrinkage of the tidal flat catchment area, the rate of change of the tidal creek morphology characteristics has slowed. However, excessive erosion has narrowed the tidal flat catchment area, resulting in a slowdown in the variation of tidal creek morphology characteristics. The changes in the morphology characteristics of the tidal creeks on the west side of the Old Yellow River Estuary are affected by seawater erosion, showing obvious stages: various morphology characteristics increased rapidly before 2016, and the growth rate slowed after 2016. (3) At present, due to the vegetation gathering on the northern and southern sides of the Yellow River estuary, most of the tidal creeks have achieved equilibrium. The bifurcation ratio of the tidal creek system at all orders showed an increasing trend, but the increasing rate slowed down, from large-scale bifurcation to local etching. Our algorithm represents a significant step forward in the high-precision quantitative detection of tidal creek morphology characteristics, and our results provide evaluable insight into the necessity of monitoring the status and evolution of tidal flats.

Channel morphology and prediction of mid-line channel migration in the reach of Ganga River using GIS and ARIMA modeling during 1975–2020

AbstractThe dynamic nature of meandering poses several challenges in a river. The river Ganga shows severe bank erosion in many of its stretches which creates insecurity to the habitats. In the present study, channel morphology and lateral mid-line migration for 1975 to 2020 in 5 years intervals have been studied. The prediction of lateral mid-line migration from 2020 to 2050 by using multi-temporal Landsat satellite images was made by using the ARIMA model. The river reach was divided into 8 bends and 48 cross-sections were identified. The channel length was observed as 224.35 km in 1975 which reduces to 199.96 km in 2020. A decreasing trend was observed for the mean of channel length and meander ratio, and an increasing trend was noted in the mean of sinuosity ratio and tortuosity ratio. A total of 11 cross-sections showed the rightward shifting and 36 cross-sections showed the leftward shifting. Observed and predicted values showed a good R2 value of 0.90 and 0.89 at CS-24 and CS-25, respectively. The results may be used for planning and management of various river training work and understanding the river system dynamics.

Planform Dynamics of Kankai River using GIS and Remote Sensing

The Kankai river is a rainfed perennial river of eastern Nepal and carries a large quantum of silt, and enters in Kishanganj of West Bengal, India. Recently, a bridge collapsed in a village in the Kishanganj district due to a rise in the water levels of the Kankai river. This paper presents a study of the dynamics of changes in channel planform and measurement of the erosion and accretion of the Kankai river in Bihar, India from 2000 to 2018. Spatial data were processed in GIS to determine the changes in sinuosity, centreline migration rates, and extent of erosion, and deposition of sediment. The maximum river shift was obtained as 800 to 1600 m and the minimum river shift varied from 6 to 70 m. With a sinuosity ratio for the whole reach of the river of 1.45, the Kankai river is considered a sinuous river and needs river training works at the erosion sites.

Morphotectonic Evolution of the Siwalik Hills between the Yamuna and the Markanda River Exits, NW Himalaya

ABSTRACT The Main Frontal Thrust (MFT) marks the present day active deformation front of the Himalaya and separates it from the Indo- Gangetic plains. The dynamic growth of the outermost Siwalik hills due to thrusting along the MFT has a direct influence on the drainages which collectively control the landform evolution of the region. In this study, the Siwalik hills (called as the Dhanaura range in the study area) between the Markanda and the Yamuna river exits in the NW Himalaya is investigated for its morphotectonic evolution using geomorphic indices, longitudinal river profiles, and topographic profiles. The results suggest presence of at least four structures that have merged to form the Dhanaura range. The first expression of the Siwalik hills was marked by the uplift of the surface due to a blind thrust in the northwestern part of the study area, followed by the growth of the Pataliyon anticline along a northeastern segment. The growth of the Dhanaura anticline occurred later by the merging of three MFT segments in the southern part of the study area. The Dhanaura anticline formed a barrier to the drainages arising from the initial northern topography, forcing them to get deflected. There also exists an unidentified structure to the north of the Dhanaura anticline as evident from the longitudinal river profiles, structural data, and drainage network of the area. Low mountain front sinuosity ratio, moderate hypsometric integral (HI) values and tilting of drainage basins in the study area suggest the structures are active.

Investigating topographic metrics to decipher structural model and morphotectonic evolution of the Frontal Siwalik Ranges, Central Himalaya, Nepal

The fold-and-thrust belt in the Himalayan front is marked by the upliftment of the Frontal/Outermost Siwalik Hills along the Main Frontal Thrust (MFT). These frontal ranges display distinct morphology with prominent curved/stair-stepped and overlapping segments in the central Himalaya. In this study, we analyse the structural framework, morphology, growth and relative uplift rates of the frontal ranges in the central Himalaya, using various topographic metrics. The results suggest that the frontal ranges are folds developed along six MFT segments that have interacted to form the present day topography. These segments are also overlapping in some areas, thus, resulting in stress partitioning. We also identify a NW-SE trending pre-existing tear fault in the region that forms barrier to the growth and propagation of the MFT segments and the frontal ranges along it. The uplift rates are generally lower on relatively older fault segments due to initiation of the younger overlapping faults. It is supported by the results of the morphometric indices as the older and less active MFT segments yield high mountain front sinuosity ratio (1.3–2.2) and valley floor width to height ratio (3.3–14.6), and low values of steepness index (0.2–0.8) and hypsometric integral (0.4–0.5). Growing folds along the MFT segments have resulted in the deflection of the Narayani and the East Rapti rivers. We establish a model for the initiation and growth of various structural segments in the study area and the resultant drainage reorganisation.

Parametrizing tidal creek morphology in mature saltmarshes using semi-automated extraction from lidar

Coastal saltmarshes provide a range of ecosystem services, such as flood protection and carbon sequestration, but face rapid global losses. Managed realignment (MR) is an increasingly popular method to artificially recreate these habitats by reinstating tidal regimes to reclaimed land. However, to improve MR design, better knowledge of the processes that control morphological evolution in natural saltmarshes is needed. In this paper, we develop tools to assist in the monitoring of creek network evolution towards dynamic morphological equilibrium, a state of landform stability under current physical forcings. Using lidar (Light Detection and Ranging) datasets, we combined a semi-automated creek extraction algorithm, based on elevation and slope thresholds, with a novel algorithm for morphometric creek analysis. A comprehensive suite of morphological creek characteristics was extracted for 13 natural British saltmarshes, including: amplitude, length, sinuosity ratio, junction angle, width, depth, cross-sectional area, creek order, bifurcation ratio, drainage density, and drainage efficiency. Results closely matched with field-validated manual digitization results, and were significantly faster and less subjective to produce. Morphological equilibrium relationships from the literature were found to be applicable to the new dataset, despite yielding high prediction errors due to the inherent variety of creek network shapes in saltmarshes. New equilibrium relationships were also defined relating the creek network drainage efficiency to the mouth cross-sectional area and the marsh elevation. To improve future scheme designs, these tools will be used in further studies to monitor rates of evolution towards equilibrium in MR sites depending on their initial conditions.

Predictive Dynamics of Channel Pattern Changing Trends at Arial Khan River (1977-2018), Bangladesh

Arial Khan River is right bank distributary of Ganges-Padma River systems flowing southwest region of Bangladesh. It is morphologically very dynamic meandering river: where the delta-building process is more active than other distributaries of Ganges-Brahmaputra-Meghna (GBM) River basin. This study analyzes, morphological variables- channel length, valley length, channel area and channel patterns of Arial Khan River. A major portion of this river divided into 8 reaches from starting point Faridpur to outlet point Barisal district in order to measure channel pattern changing trends. For the proper accomplishment of the findings section of this research, time-series satellite images (Landsat MMS, Landsat TM, Landsat ETM+ and OLI) of the year 1977 to 2018 has been taken for delineation of the morphological parameters using GIS and RS techniques. In this research, sinuosity ratio index technique has been applied to analyze the morphological parameter- channel pattern and its changing trends. From the satellite images analysis results over time span, it is observed that significant morphological changes have been occurred in the river length, valley length, river area and its channel patterns. Likewise, the hydro-morphological parameters of this river (e.g., discharge, flow velocity, the river depth, width and pattern) also significantly changed due to combined massive sediment deposition from Ganges-Padma and Brahmaputra-Jamuna River systems. These hydro-morphological changes increased flood hazard vulnerability, bank erosion and sand carpeting; which badly impacted on ecological diversity, agriculture system, rural settlements and transportation networks.

Evolution analysis of miocene channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf) using seismic meta-attributes

Tectonic movement of Oman Orogeny and Zagros Orogeny and Hormuz Salt triggering are accompanied with presence of complex structures in Strait of Hormuz sedimentary basin. Geological model Obtained via multi-attribute analysis and the extracted geobodies are used to define type and relative age of channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf). In this study, channels and faults were mapped using meta-attributes by a neural network. The probability volume helps more accurate extraction of channel bodies and fault planes. The channel bodies and fault planes can be revealed more continuous with dominant edges and subtle flexures as obtained results based on meta-attributes. Considering this approach, three distinct channel types (small (S), median (M) and large (L)) are illustrious in different substrates based on various flow powers that extended from West to East. Normal fault band with the NorthEast-SouthWest trend and few dip toward the East, whereas faulting may occur during late Mid Miocene- Early Upper Miocene. The main channels (M) and (L) are located on both sides of the fault in lower and upper deeps within Mid Miocene Mishan Formation sediments, while channels (S) located away from the fault within Upper Miocene-Pliocene Aghajari Formation sediments. Processes of sediment transport are very different in Miocene Aghajari and Mishan Formations as form of meandering channels and their slopes are dissimilar. Sediment supply has led to changing geometry of meandering channel due to effects of sea-level change. Based on seismic attribute study, slope and form of channel (M) has been affected by later faulting, whereas slope and form of channel (L) operated independently. Presence of meandering channel (M) with lower slope and higher sinuosity ratio in comparison with meandering channel (L) suggests that channels located in upper horizons of sedimentary basin could be consider as an appropriate place for hydrocarbon accumulation in intra Mid Miocene Mishan Formation. Furthermore, revealed channels within Mid Miocene Mishan Formation sediments are bigger than the channels within Upper Miocene-Pliocene Aghajari Formation. Reservoir properties study suggests that channel filled sediments are relatively porous than their backgrounds, producing relatively higher reservoir potential based on the integrated analysis of acoustic impedance and frequency content.

Bank vulnerability and avulsion modeling of the Bhagirathi-Hugli river between Ajay and Jalangi confluences in lower Ganga Plain, India

The emergence of the study of fluvial dynamics of the alluvial monsoon rivers especially in India is being enriched through the application of remote sensing and GIS techniques. To study fluvial dynamics over time, channel avulsion no doubt is one of the most considerable phenomena. The study section (~75 km) in between the two confluences of the Bhagirathi River i.e., Ajay (Katwa) and Jalangi River (Nabadwip) confluence in Lower Ganga Plain of West Bengal is highly oscillatory in nature. Several satellite images and toposheets of different time periods (1955, 1973, 1990 and 2011) have been used in order to analyse the avulsive nature in this section of the river. These fluvial features (cut offs, ox-bow lakes, point bars etc.) form as a result of channel avulsion and have been identified with the help of Landsat satellite images. The decadal differences in sinuosity ratio in different parts of the studied section, channel migration rate and avulsion model explain the dynamic nature and crucial portions of high bank erosion rate of the channel in the mentioned time period. For both the reaches (R1 and R2), meander loop cut offs are dominant rather than lateral avulsion in the context of aggregate channel migration that also reflects the instability and erosional vulnerability at different meander bends.

Assessment of Fluvial Channel Dynamics of Padma River in Northwestern Bangladesh

Fluvial channel form and its dynamics over the period of time have been a major interest of study in fluvial geomorphology. The present study deals with the fluvial morphological characteristics of the Padma River in northwestern Bangladesh. Morphological and morpho-dynamic maps of the Padma River were prepared using remote sensing techniques. Sinuosity ratio, braided index and island percentage of the study area were estimated for the year of 1977, 1989 and 2000 respectively. Results showed a remarkable change in position of bank and channel as well as bars along with their geometry and morphology over time. Result also demonstrates that the bank line is unstable and migrated continuously towards westward in the recent decades. In addition, the study reveals that overall width of the Padma River is varied significantly during the last 23 years. Different maps and Landsat images (band 4) depict that the river shifting is abnormal which is alarming for the existence of the study area people. Outcomes of this study obtained from investigating satellite remote sensing imagery provide valuable information about the bank erosion and channel shifting of fluvial morphology of the Padma River and to recommend some protective measures.

Neotectonic Activities in Northern Saurashtra Peninsula Bordering Gulf of Kachchh

This study points out the evidences of neotectonics and possible existence of active fault in northern part of Saurashtra Peninsula. The methodology used for the detection of neotectonism are: a) analysis of numerical data obtained from Digital Elevation Model (DEM) and its derivatives (morphometric indices), b) study of geomorphic markers and c) correlation of seismic & palaeoseismic data and geomorphology with structural lineaments. Morphometric indices such as drainage density, stream frequency, bifurcation ratio, basin length, basin relief, relief ratio, elongation ratio, stream gradient index, hypsometric index and sinuosity ratio have been used to assess the tectonic signatures. Morphometric indices suggest that Aji river basin is tectonically active, whereas Und and Sasoi river basins show some of the parameters in active tectonic range. Regional study using remotely sensed data (Landsat OLI multispectral) has helped to show a) about 100° dextral rotation of Aji river trunk channel near the Gulf coast and b) dextral deflection of both Aji and Und river about 25 km from the coast. Study of a segment of Aji river basin near Ranjitpura- Balamba proved upliftment and tilting of land resulting a) narrowing of trunk channel towards sea, b) development of new sets of channels over tilted river terrace, c) development of beheaded channels, d) presence of palaeo-channels and palaeo-delta in different directions with the present ones and e) formation of estuary with definite geometric shape. Occurrence of earthquake epicentres, in conformity with predicted lineaments in addition to paleoseismic records supports the existence of the fault. On the basis of integrated evidences it has been established that the Saurashtra coast along the Gulf of Kachchh is tectonically active with the existence of a dextral strike slip fault (ENE-WSW trending) with a rotational component manifesting tilting of the northern block towards east.

최소차 하천의 임계면적에 따른 유역 지형매개변수의 변화특성

The size of minimum order stream has a very sensitive effect on runoff analysis model using the divergence characteristic of stream. Therefore, in this study, the threshold area of minimum order stream has been examined the change characteristic of topographical parameters. The subject basin of the research was the upper basin of the Kumho water gage station which is located in the middle of the Kumho river. The 1:25,000 numerical geography which was constructed <TEX>$10{\times}10m$</TEX> mesh was used. The range of investigation of topographical parameters are number of stream order, length, area, slope, basin relief, sinuosity ratio, drainage density and total stream length etc. It was found from the result of analysis that the threshold value of minimum order stream has a very big effect on topographical parameters of basin. It was found that the threshold area of minimum ord er stream revealed under <TEX>$0.10km^{2}.$</TEX> Furthermore, the parameters showed a serious change except for over <TEX>$0.10km^{2}.$</TEX>