Models and Monte Carlo Simulations of the Mean Sinuosity of Major Meandering Rivers

The purpose of this research is to investigate the sinuosity of major rivers in the United States and the world, and to compare them to that predicted by the existing theories. It is shown that the average sinuosity of meandering rivers deviates considerably from what has been reported previously as π. Calculations of the mean value of actual sinuosities of major rivers in the United States and in the World show that this average is very close to 2. Exact models as well as a Monte Carlo simulation for meandering rivers that is based on Gaussian probability distribution function are also presented, and the possibility of composite meandering is discussed.

Morphodynamic Changes of Bhagirathi River at Murshidabad District Using Geoinformatics

The channel of Bhagirathi River is the branches off from the Ganga at Nurpur (lower course of the Ganga). Bhagirathi River is one of the main rivers in Murshidabad district. Analyzing the image of the Bhagirathi River in Murshidabad district through the year 1970, 1977, 1990, 2000 and 2006, it is found that significant changed has been occurred in souththern part of the river and less change is found in the middle part which is close to the Berhampore town. Toposheet of the year 1970 is also compared with the image data to observe the change. Water discharge, soil types and transportation of sediment is the major contributing factor of morphological changes like bar or shoal, ox-bow Lake, meander etc. Maximum erosion takes place at Dear Balagachi and after Baidyanathpur. A cut-off has take place at Baidyanathpur in 1984 [1]. It is found from the study that there is a possibility of natural meander cut-off at Dear Balagachi and near Majayampur. The traditional bank protection works, concrete walls, cemented stone and brick, play a significant role in the modification of the hydraulic aspect of the discharge values and in the interference in the water dynamics of erosive and depositional phenomena both upstream and downstream.

Quantitative Methods for Comparing Different Polyline Stream Network Models

Two techniques for exploring relative horizontal accuracy of complex linear spatial features are described and sample source code (pseudo code) is presented for this purpose. The first technique, relative sinuosity, is presented as a measure of the complexity or detail of a polyline network in comparison to a reference network. We term the second technique longitudinal root mean squared error (LRMSE) and present it as a means for quantitatively assessing the horizontal variance between two polyline data sets representing digitized (reference) and derived stream and river networks. Both relative sinuosity and LRMSE are shown to be suitable measures of horizontal stream network accuracy for assessing quality and variation in linear features. Both techniques have been used in two recent investigations involving extraction of hydrographic features from LiDAR elevation data. One confirmed that, with the greatly increased resolution of LiDAR data, smaller cell sizes yielded better stream network delineations, based on sinuosity and LRMSE, when using LiDAR-derived DEMs. The other demonstrated a new method of delineating stream channels directly from LiDAR point clouds, without the intermediate step of deriving a DEM, showing that the direct delineation from LiDAR point clouds yielded an excellent and much better match, as indicated by the LRMSE.

Morphometric Assessment of Meandering River in Arid Region Using Improvement Model (Case Study: Maroon River)

To understand the natural environments of drylands, deserts, arid and semi-arid regions of the earth is to understand the processes and forms of their rivers. One of the river studies and fluvial processes are morphometry analyses. The channel forms in an alluvial plain reflecting the movement of water and the particle size of the load flowing down the channel. The dynamics of channel change has led to conflict with human resource development. Three basic channel patterns are detected in the region. They are braided, meandering and straight. In this research for assessment of meandering Maroon River, we used DEM (Digital Elevation System), Topography maps, Arc GIS software, Google earth, field work and library studies and mathematic formula. The two general indices for analyzing meandering patterns are 1) sinuosity coefficient 2) central angle. In this paper, the authors were used these factors and improved them. One of the results is creation of direction index and the second result is the Maroon River which has a type of sinuosity in any reach.

Evaluate Tectonic Activity of Tehran City (Iran) Based on Geomorphic Indices, Field Investigation and Remote Sensing Study

Active tectonics in the south part of Alborz Mountain (Iran) has greatly influenced the drainage system and geomorphic expressions. The metropolis of Tehran is located at the southern foothills of the Alborz Mountains at the abrupt topographic boundary between the mountain range and the northern border of the central Kavir Desert. The presence of active faults and tectonic activity, threatens the area and shows the vulnerability of this Tehran city. So the evaluation of active tectonics of Tehran City is necessary because of vast human activity, which has hidden geomorphic feature. Active tectonics of Tehran City was evaluated by using Digital elevation model (DEM) derived drainage network and three geomorphic indices basin (asymmetry factor (AF), basin shape index (Bs) and mountain front sinuosity (Smf)). The average of the three measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. Furthermore to overcome some inevitable error in this method, field investigation was carried out also remote sense was studied, and finally the obtained results were compared with existing seismic data. The result confirms that the East South, East North and West North Tehran have high rate of relative tectonic activity (RTA) respectively.

Assessing the oscillation of channel geometry and meander migration cardinality of Bhagirathi River,West Bengal,India

Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ～67.30 km between the confluence point of Ajay and Jalangi rivers in East Burdwan and Nadia districts of West Bengal. The course of Bhagirathi is notably migration prone and cultivates problematic changes along its course over time. In the study, we have looked into its migration tendency and unpredictability for past 238 years and then predicted the lateral shifting of river centerline using temporal satellite imageries – Landsat-5(TM) of 1987(8, December), 1995(28, January), 2005(7, January) and LISS-IV satellite imagery(2017, 5 January);SOI Toposheet – 1968–1969(79 A/2, 79 A/3, 79 A/6 and 79 A/7) and Rennell's map of 1779. Other highlights are the quest of fluvial features, oxbow lakes, mid-channel bars, channel migration rate, meander geometry, channel sinuosity in different parts of river course and the parts that experience intensive bank erosion. The entire river course has been subdivided into three segments; viz. reaches A, B and C. Investigation displays that degree of sinuosity decreases from its anterior course(1968) to the existing course(2017). Reach-specific outputs display that reach B is highly sinuous(SI value 1.94 in 2017) and SI increases temporarily, whereas for reaches A and C it decreases with time. The rate of migration is higher in reach B than that in reaches C and A. The study displays a notably decreasing trend of migration in comparison with its previous lateral migration and shows that the migration nature over time is intensively inconsistent and unpredictable except very few portions of the river course. The nature of deposition within the river channel shows an unstable behavior during the entire period of the study. Meander geometry depicts a rapid change of river course innate to meander bends and shows a higher rate of migration by meander loop cut-off rather than lateral migration that reflects the inconsistency, erosion vulnerability and unpredictable nature of migration. The present work offers a valuable source to comprehend channel changes in Bhagirathi River and serve as an efficacious base for river-bank migration and erosion hazard planning and management.

Role of flood discharge in shaping stream geometry:Analysis of a small modern stream in the Uinta Basin,USA

This small modern river system is located on a retativety flat （about 1°-2°）, unconsotidated sandy pediment surface in the Uinta Basin of Utah, USA, and it is with a scare of about 30 m tong and 0.4-0.8 m wide, simitar as a natural flume experiment modet. The smart stream is informatty divided into upstream, midstream and downstream. The anatysis shows that flood discharge influences channet sinuosity and morphology to produce an initiat meandering pattern which is tater changed to a braided and then a straisht pattern in the downflow direction. The upstream segment has a hish sinuous geometry dominated by both erosion （cutbanks） and deposition （point bars）. In the resistance of sporadic vegetation rooting in banks, the upstream flood deviates its original direction, which resutts in the powerful flood intensively eroding the cutbank and accreting clastics to build point bars, and thus producing a high sinuous channet. The midstream is dominated by deposits （many smart bars） with a moderate to tow sinuosity. Due to the bad drainage of the high sinuous channel in the upstream, the strong flood can cut off the point bar comptetely or even surmount the tevee in the fast meandering upstream, which widens the channel suddenty with a quick decreasing current power. Then, the ctastics from the upstream are untoaded in the midstream and form many smart bars. Untoaded sediments protect the bank, and the tow-power current brings a moderate erosion to the bank, which forms a moderate to tow sinuous channel in the midstream. The downstream shows multistage erosionat terraces in its retativety straight channets. After the midstream water drops its toad, it becomes ＂dear＂ and reaches downstream, the tower current power is hetptess to reform channet 8eometry. Thus, the downstream channel sesment keeps a tower sinuous geometry, evenstraight partially. Small amounts of fine clastics are deposited, and simultaneously multistage terraces are formed due to regressive flood erosion. This stream example demonstrates the subtleties of stream flow and the importance of flood discharge in shaping the channel geometry. Although it is difficult to scale up this example to a large river system that carves geomorphic landscape, this case shows how river geometries vary from the traditional patterns due to different gradient.

Evolution of river course and morphometric features of the River Ganga:A case study of up and downstream of Farakka Barrage

River channel shifting in the deltaic regime is an unabated occurrence.Channel shifting has become one of the concerns as it influences land use/land cover along the riverbank in various ways.For the management of the river,it is indispensable to study the pattern of river course change both in qualitative and quantitative methods.This study is an attempt to understand the pattern of shifting and to quantify erosion and deposition of the river Ganga at upstream and downstream of Farakka Barrage during 1794-2017.The study has been carried out by using various historical maps,aerial photographs,satellite imagery,and remote sensing and GIS technique to understand the dynamic of the river.Over 223 years period shifting of the river accentuates the remarkable oscillation of the river.Perimeter of the river is determined to understand the area covered by the river course in the study area.To evaluate the meandering of the river sinuosity of the river has been computed in this study.The amount of erosion and deposition was calculated in this study by using ArcGIS 10.6.The study found a higher amount of erosion at the east bank where Manikchak,Kaliachak II and Kaliachak III blocks are situated between 1965 and 2017.At the west bank of the river,especially the Rajmahal block,the occurrence of deposition was remarkable during the same period.