Channel avulsion in Jiadhol River of Brahmaputra basin

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.

Geology, 2013

The August 2008 avulsion of the Kosi River, northern India, resulted in a maximum eastward shift of >100 km and created an avulsion belt of 2722 km 2 . Based on A.D. 2000 Shuttle Radar Topography Mission data and on 2005 Landsat Thematic Mapper satellite imagederived channel network (pre-avulsion), we use a topography-driven connectivity model to simulate the avulsion pathway, which corresponds, to a large extent, to that observed in the post-avulsion period. We then use this model to postulate the avulsive course of the river from another upstream point based on avulsion threshold analysis.

Journal of the Indian Society of Remote Sensing, 2018

The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the channel morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral channel bars, braided channels, back swamp, rapids, pools and river souls were identified in the channel course of the river. Shifting of the channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2-5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting channel.

2018

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 tr...

http://eprints.soton.ac.uk/id/eprint/347113, 2012

The Landsat programme, which started in 1972, initiated an era of space-based Earth observation relevant to the study of large river systems through the provision of spatially continuous, synoptic and temporally repetitive multi-spectral data. Free access to the Landsat archive from mid-2008 has enabled the scientific community to reconstruct the Earth’s changing surface and, in particular, to reconstruct the planform dynamics of the world’s largest rivers. The present research reconstructs the planform dynamics in the lower reaches of one of the Asian mega-rivers, the River Ganga-Padma (Ganges), from 1972-2010 using the Landsat archive. The research based on sequential river planform maps generated from the time series revealed a periodic pattern of evolution of the river system over the study period which began by means of meandering at four locations. The meander bends increased in sinuosity until chute cut-offs were triggered, returning the river to a state similar to that at the beginning of the sequence. This periodic pattern is constrained by natural and artificial hard points, and by the Farakka Barrage, meaning that the observed cyclic pulsing is likely to continue into the future. The characteristics and dynamics of meandering rivers have been the subject of extensive research, though the mechanisms involved are still not completely understood. Presently, availability of archival satellite sensor data at regular and frequent intervals for almost four decades presents a great potential for increasing our understanding of the natural processes of meander growth. Though early research indicates that meander growth can be explained by instability of alternate bars in a straight channel, but research based on field data and simulation models have shown that instability of river meanders is an inherent property and the meanders reach a critical value of sinuosity when cut-offs occur and then the complex system undergoes an self-adjusting process. The meander dynamics of the lower reaches of the Ganga-Padma system has been studied in the context of threshold response of a complex system. A conceptual model was developed based on spatial information from the sensor data and quantitative information on river metrics to explain the behaviour of the river system including evidence for self-organising criticality and the attempts of the river to reach dynamic equilibrium. The meandering channel pattern with a tendency of braiding of the river Ganga-Padma were explained based on existing empirical models as well as models based on mobility number and channel stabilization criterion. The threshold for chute cut-off was explored and subsequently the conditions for soft avulsion / branching were studied which showed that the condition for chute cut-off in the Ganga-Padma system is not due to bankfull flow velocity and the super elevation of flow at the centreline of channel but may be due to lack of vegetation stabilization on the Ganga-Padma floodplain. The effect of tectonics and meandering in the moderately paced avulsion of the Ganga-Bhagirathi system to the present Ganga-Padma system was modelled in the present research. It was found that gradient advantage and bend upstream of bifurcation does not result in modelled avulsion as observed in small and medium rivers and large rivers in tectonically inactive regions. A tectonic uplift results in a modelled avulsion period consistent with historical observations. It was found that backwater effect and high sediment mobility keep both bifurcated channels active to attain an anabranching pattern. The backwater effect was found to play an important role for sustaining the anabranch planform of many of the largest rivers of the world.

Geomorphology, 2014

Models for river avulsions have identified the ratio between down-valley and cross-valley slopes of channels as the triggering factors for the sudden channel shift but have remained untested in the field. The August 2008 avulsion of the Kosi River at Kusaha, 12 km upstream of the Kosi barrage in Nepal, provided an opportunity to study a large-scale avulsion (~120 km) for its causal factors and driving mechanisms. We used the SRTM-based digital elevation model and remotely sensed data coupled with field topographic mapping with a kinematic GPS and a Total Station to characterise a~50-km-long stretch of the Kosi River. We have computed reach-scale avulsion threshold index (ATI) integrating SRTM-derived slopes and planform dynamics on a GIS platform. We show that several reaches along the Kosi River are avulsion-prone, including the Kusaha point that is consistent with the August 2008 avulsion. We suggest that apart from cross-valley and down-valley slopes, planform dynamics such as thalweg shift, sinuosity variation, and channel multiplicity significantly influence the avulsion threshold in alluvial reaches of the rivers such as the Kosi.

Journal of Geography & Natural Disasters, 2013

Channel changes with respect to time and space play a significant role in stream flow dynamics. The rambling and trailing of channels in the studied region has been studied through systematic analysis and interpretation of diverse channel configuration and multi-channel orientation using multi-temporal Topographical maps and Satellite images for a period spanning nearly 80 years (1930-2011). For this specific purpose lower course of Diana River in the Jaldhaka-Diana river system has been selected in the Duars region of the Jalpaiguri district, West Bengal which is virtually a zone of transition between the Himalayan Mountains and the North Bengal plain. The prime objective of the study is to reveal the spatio-temporal sequences of channel changes, consequent movement of confluence point and the factors and causes of such movement. For this particular extraction, Base map has been generated with the help of SOI Topographical maps and satellite images of the respective area. For this purpose updated version of ERDAS Imaging is employed as image processing tool for enhancing, merging and to update the spatial information of channel configuration and Arc GIS for final product generation. Following the specific objective of the study it has been deduced that during this span the confluence point has moved and reoriented both upstream and downstream on a historical time scale and new confluence points have been created by repeated shifting and migration of channels. No definite trend is observed in the movement of the confluence points. However, but it is noticed that some distinct flow dynamics and channel maintaining processes are actively performing in this spatio-temporal analysis of channel changes.

International Journal of …, 2003

ABSATRACT Morphological analyses require quantitative description of river course by providing its equation. Such an equation is not possible as the river plan-form contains loops that cannot be described by it. To circumvent this difficulty a system of parametric equations is ...

Current Science

In the present study, instability of the river reach of Brahmaputra was analysed for braided belt width changes, braiding index and bar area. The river reach of the Brahmaputra from its confluence of Lohit, Dibang and Dihang to its confluence with the Tista river was studied from 1973 to 2009. The study was carried out using remotely sensed data from Landsat satellites at different dates. Discharge data synchronized with satellite data was collected by maintaining near-similar water level or discharge. Wavelet of the braided belt change was analysed to get the wavelet power and spatial extent of the changes. Finally, stream power was analysed from the average discharge data during the monsoon period to determine its effect on the instability of parameters considered. Results indicate that stream power does not directly relate to local changes in the braided belt or braiding index. However, with decrease in stream power, an increasing trend of bar area was found. Maximum wavelet power within a period showed a threshold behaviour at stream power of 5 W/km, beyond which the wavelet power raised sharply to a high value with increase in stream power. River response to the stream power was found at a global level rather than local level. Finally, a gradual decrease in stream power over time indicates the stable river reach. However, changes due to local bank erosion cannot be predicted using this analysis.

European Scientific Journal, 2014

Since ages people and rivers have been closely associated with and a slight change in behavior in any aspect has serious repercussions upon the other. Brahmaputra-the lifeline of about 264 lakh population of Assam, has been intrinsically related with the way of life of the inhabitants within its domain and has both positively and negatively affected them. Bank line migration and consequent channel shift is a common phenomena of the mighty river due to its high braided condition and host of other geological as well as other hydrological factors. The study incorporates the Agyathuri-Sualkuchi stretch of Kamrup district, within 5 kms downstream of the Saraighat bridge (the first bridge over Brahmaputra), where the river shows strong northward migrating tendency. Major changes and displacements have been taking place in the region due to channel shift. Keeping in view all these aspects, the paper tries to examine the extent of area encroached by the river since 1911 to 2005 and thereby analyse the causes responsible for channel shift. The specified objectives have been fulfilled based on the utilization of toposheets and google maps in GIS environment including personal field visit. Necessary maps and diagrams have been prepared for exposition of the problem.