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1.
Rivers flowing through the alluvium invariably have very low gradient forcing the river to flow slowly in a meandering and zigzag path. Nature and intensity of meandering is governed by the geological and tectonic conditions of the river basin. Barak River in tectonically active south Assam (Northeast India) exhibits intense meandering and shifting of the river course. Topographic data of two different years and satellite images of 4 different years covering a section of the Barak River have been investigated to verify the nature of changes undergone by the river through times. This study reveals active northward shift of the river and a prominent neck-cut off in the initial part of the study area. Northward shift of the river also occurred in the area west of Silchar. But, in the western part the river has shifted both towards north and south. Oscillatory shifting in the river channel has also been noticed. The river has shown a overall northward shift which is probably due to uplift of the southern part of the Barak River valley.  相似文献   

2.
Channel migration includes any change of river channel geometry within the context of the cross-section, pattern or network in a drainage basin. To study the dynamic behaviour of a river, measurements taken with conventional ground-based instruments are time-consuming and expensive. Remote sensing techniques are capable of providing a measure of surface variability including dynamic behaviour of channels, reasonably quickly due to availability of the repetitive remotely-sensed data. These data are well suited for the assessment and monitoring of dynamic changes on the surface of the earth. In the present study Landsat MSS and TM data of winter season in the form of false colour composites (FCC) of years 1982 and 1987 were used for the delineation of river Ganga course lying between Allahabad and Buxar. The interpretation of satellite data was carried out using visual interpretation technique for the assessment of channel migration. The shift in river banks delineated from satellite data were measured with respect to river banks identified from topographical base map. The maximum shift observed in mid channel is 4. 55 km while maximum left and right banks shifts are 4.6 and 4.8 km, respectively.  相似文献   

3.
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.  相似文献   

4.
Satellite remote sensing technique can be effectively utilised in mapping and monitoring the river course changes and associated geomorphological features. Ravi river, flowing along the Indo-Pakistan border, has been in the limelight for its repeated flood havoc during monsoon and abrupt encroachment at some places in the Indian territory, where it was not flowing earlier. This river, meandering in zig-zag fashion along the International boundary in Amritsar and Gurdaspur districts of Punjab, poses perennial threats to the nations’s economy due to extensive destruction happening every year. An attempt has been made to map the shift of this river and the associated geomorphological features along its course using the Indian Remote Sensing Satellite data (IRS-IA and IB LISS-IIFCC) of the period 1991–1993 and the Survey of India topographic sheets of the period 1972–1973. The study shows that there has been drastic changes in the course of Ravi during a span of 20 years due to human activities along its course. The river has shifted its course considerably towards India since its topography is against it. River training structures/bundhs, built by the neighbouring country, across and very near to the earlier river course has been the main reason for this drastic shifting. It is estimated that such massive structures could turn the river course towards India by atleast 1 to 5 km in the border districts of Punjab. This shifting of Ravi along international border poses a serious threat to the Nation’s defence system.  相似文献   

5.
Both surface and subsurface evidences exist along the longitudinal section of the Ganga river in Kanpur-Unnao region of Central Ganga Plain indicating the effect of tectonic subsidence. While the surface evidences are discontinuous chain of high uplands with escarpments on the southern bank of the Ganga river and the wide flood plain on the northern side, the subsurface evidences are in terms of sudden deepending of the granitic basement towards north followed by deposition of coarse sand and gravel forming thick aquifers in the close vicinity of present channel of the Ganga river. The petrological examination of the aquifer material also indicates that the material has been derived from a deformation zone.  相似文献   

6.
The Burhi‐Gandak river is one of the major tributaries of the Ganga River in the middle Ganga basin. The river is i known to have an oscillatory character and has changed its course in Recent times. In the present study, a variety of remote sensing data combined with surface and subsurface data have been used to delineate the fluvial palaeofeatures of this river. The palaeofeatures of the Burhi‐Gandak indicate that the river has shifted from N to S over a distance of 30 km. Further, its is observed that Burhi‐Gandak river had a larger channel width and higher discharge on earlier times and was very active. On detailed examination, a past link between the now northerly flowing Baghmati and Burhi‐Gandak rivers is detected. Based on the above features, three distinct stages of migration of the river have been identified and a summary of fluvial palaeohistory is presented.  相似文献   

7.
Ganga is one of the largest rivers of the world which supports millions of population on its banks. It is a tectonically controlled Himalayan river which also creates havoc due to perennial floods every year. Like most large river systems, it also shifts its course in the Gangetic plains in space and time. The present study measures the variable shift in a selected flood-prone stretch of the Allahabad city lying on the western bank of the Ganga river, taking into account the historical, annual to monthly data (including pre- and post-monsoon shifts) to show the ongoing changes in the river course with possible causes and futher implications. It also discusses for the first time the down stream effect of the Tehri dam on the Ganga river course after it became functional.  相似文献   

8.
The anomalous channel pattern in the midland stretch of the river Karamana, having highly sinuous and incised course with varying floodplain, is analysed to determine the different stages of evolution of the river channel in response to the structural disturbances in the area. Geometric analysis of foliation, geospatial analyses of sinuosity index, hypsometry, channel and streamline changes, river channel cross-profile, longitudinal profile and derivation of fold structure from satellite images were attempted in evaluating the characteristic features of the selected river segment. Datasets used in the analysis were collected through the detailed fieldwork, structural mapping and interpretation of satellite images and satellite-derived digital elevation data. Systematic analysis of the channel pattern of the selected reaches of the river, in 1915, 1968 and 2008 classifies the river as tortuously meandering. Implications of tectonic disturbance can be inferred from the presence of channel incision, unpaired terraces, younger terrain with intense erosion, knick points, convex river long profile, and high hypsometric integral, oscillating and unpaired character of the river channel. Structural analysis along with GIS and remote sensing studies proved the presence of a major fold with a NW–SE-trending axial surface. An evolutionary model is proposed to elucidate the channel planform changes in response to the deformation and tectonic uplift of the region.  相似文献   

9.
Alfios is the biggest river of the Peloponnese and the ninth longest river in Greece. It drains an area of almost 2575 km2 in Western Peloponnese and discharges at Kiparissiakos Gulf. Due to its extent, the Alfios basin presents complex physiography and geomorphology.

During the last 50 years, major direct human activities have had an important impact on the river network shape and on the valley floor morphology. The most important human activities were the channel straightening caused by meander cut-offs in 1950, the construction of two dams: the Ladonas dam in 1955 and the Flokas dam in 1968 and the illegal in-stream gravel extraction that started in the 1960s and continues until today. As a result, the Alfios riverbed has presented very rapid vertical and horizontal (lateral) erosion and significant changes to its network shape. The drainage network follows a straighter course, the number of meanders has been reduced and the seventh order branch is deeply incised. Besides the morphological impacts to the river network shape there are also serious economic damages caused by human activity. During the winter of 1999, the Flokas dam bridge was closed for a long period due to damages at its foundation caused by the heavy rain and illegal gravel extraction. Transportation between the villages in the area became extremely difficult and time consuming and the cost of the repairs was estimated at 500 000 euros. In this study, there is an effort to map the network shape transformation for the period 1977–2000 using multitemporal and multisensor satellite images. One Landsat MSS image, three Landsat TM images, two Landsat ETM images, and one Terra ASTER image have been orthorectified and processed in order to cover the specific period. Principal Component Analysis (PCA) method and Geographical Information System (GIS) techniques have been applied to map the changes in the Alfios River channel. The drainage network straightening and the cut-off of five big meanders were detected and mapped. These changes occurred between 1986 and 2000.  相似文献   

10.
Bist Doab interfluvial tract in the north-western part of Punjab, India, has been investigated for geomorphic signatures of active tectonics using remotely sensed data and geographical information system (GIS). The anomalous river flow, abrupt changes in flow direction, angular drainage, compressed meanders, asymmetry of river bends, high channel sinuosity, abandoned channels, water-logged and marshy areas observed along the courses of Beas and Sutlej rivers and their tributaries indicate tectonically active nature of the terrain. The strong control exercised by the NE-SW and NW-SE trending lineaments on the drainage network is well evident in the form of long straightened slope deviatory courses, definite changes in channel pattern and sharp knee bend turns taken by the seasonal rivulets. The asymmetric and elongated nature of watersheds and straight to curvilinear mountain fronts quantified through morphotectonic analysis are characteristic of tectonically active settings and further corroborate the evidence of active tectonics.  相似文献   

11.
Hydrogeological studies in the Quaternary alluvial plain of a part of Azamgarh and Ghazipur districts, using air photos on scale 1:60,000 indicate the presence of five hydromorphic units namely, Alluvial upland, older alluvial plain of Mangat-Besu, older flood plain of Ganga—Gomti, youngest terrace of Ganga—Gomti and present flood plain of Ganga-Gomti. From the groundwater point of view older flood plain of Ganga—Gomti is the most promising hydromorphic unit. Abandoned channel of river Ganga offers favourable site for deep groundwater exploration with high potentiality. Chemical quality of shallow and deep aquifers is suitable for irrigation and other purposes.  相似文献   

12.
In this study, visible near infrared, shortwave infrared spectral bands of Landsat 8 satellite sensor, two polarisation channel of L band ALOS-PALASAR sensor, SRTM-DEM derived digital elevation data were processed to delineate different geomorphic components of alluvial fans of Tista-Mahanada fan complex. We found image composite of independent components, principal components of Landsat 8 bands were effective in delineating proximal and distal fan segments. Fused images of Landsat 8 and ALOS data were used for enhancing incised distributaries and paleochannels. Field data on depositional sequence of fans, were used to substantiate the image based delineation. Topographic breaks along selected longitudinal profiles (identified with the changes in land use and drainage pattern) of digital elevation data were conjugately analysed using Landsat false colour composites. GPR survey along selected transect highlights the vertical dislocation in the recently deposited sequences of alluvial fan regime indicative of post depositional disturbances.  相似文献   

13.
The paper describes the details of a comparative study of geological interpretations carried out from Synthetic Aperture Radar (SAR) imagery, Landsat MSS (B & W) imagery and Aerial Photographs, covering 2100 sq km of area in Anantapur district of Andhra Pradesh. The area comprises Peninsular—Gneissic Complex and rocks of Dharwar and Cuddapah Super Groups beside the Quaternary alluvial deposits along the Penneru river and its tributaries. Geomorphologically the areas is represented by denudational, fluvial and structural landforms. The study indicates that the details of the geological and geomorphological maps prepared from SAR imagery and aerial photographs are comparable despite the smaller scale of SAR imagery while the same are not exhibited in Landsat imagery mainly due to its low resolution. Although broad lithological units are possible to be discriminated on SAR as well as aerial photographs, some of the finer rock types viz. gabbroic dykes could be discriminated from the delerite dykes in the SAR imagery due to their different surface roughness. Stereoscopic coverage and enhanced micro-relief of SAR imagery gives better geomorphological details in comparison to aerial photographs. A detailed study of lineaments has also been carried out which shows that in SAR imagery there is over-representation of short lineaments due to enhanced micro-relief and radarshadow effects across the look direction and under-representation of lineaments along the look direction. Landsat imagery is perhaps the best for demarcating lineaments of regional magnitude while aerial photographs are good for depicting shorter lineaments. However, certain lineaments seen in SAR imagery are often not continuously seen on aerial photographs.  相似文献   

14.
《测量评论》2013,45(61):255-264
Abstract

The city of Colombo, capital of Ceylon, is situated at the mouth of the Kelani Ganga and about 25 miles north of another considerable river, the Kalu Ganga, which enters the sea at Kalutara. Though its proximity to two of the largest of the perennial rivers of Ceylon provides some advantages of inland water transport by river craft, it also places it in the zone of periodical floods which cause damage to buildings, communications and agriculture within the city limits and over extensive areas of low-lying paddy fields and gardens beyond. Except for a spur of high land running roughly parallel to the eastern shore of the harbour through Hultsdorp, Blomendahl and Kotahena to the loop of the Kelani Ganga near its mouth, the greater part of the city is very flat and only a matter of 20 feet elevation above sea-level. On its eastern flank lies a series of connected shallow lakes, marshes and paddy fields which extend in a loop from the banks of the Kelani Ganga at Ambatalenpahala to Dehiwela on the city's southern limit; there are, in addition, canals through this area with two outlets into the sea at Wellawatta and Dehiwela. Navigable canals connect the Kelani Ganga with the Beira Lake and Colombo Harbour and, with the canals already mentioned, form a continuous waterway which, in fact, extends northwards as far as Puttalam, 80 miles from Colombo, and southwards to the Kalu Ganga and Kalutara. About half a mile east of Mount Lavinia another series of shallow lakes, marshes and paddy fields spreads its irregular shape roughly parallel to the coast through the Bolgoda Lakes to a low ridge north of the Kalu Ganga and close to its right bank. The whole of these lowlands is referred to as the Bolgoda Basin. A canal called the Kepu Ela, constructed by the Dutch during their occupation of Ceylon, passes through it to join the Kalu Ganga at Diyagama about 5 miles from the river mouth.  相似文献   

15.
Various geomorph.ological features associated with fluvial processes of the river Satluj are mapped using photo-interpretation techniques with a view to assess the environmental status of the area in the north-east of Ludhiana (Punjab State). Features mapped include braided river channels, oxbow lakes and meander scrolls. The younger alluvium supports good vegetation and cultivation because of -shallow depth of water level; though prone to annual floods in the lower levels and major floods in the higher levels. It is saved from these hazards by providing bunding on both sides of river isolated sand deposit patches have been demarcated in the older alluvium. Shifting of the main river channel towards north is noticed as it has gradually shifted from its earlier course which lies towards south.  相似文献   

16.
The study of lineament pattern based on IRS-IA sub-scene (P24–R50) and Landsat (P143– R42) data combined with the drainage analysis and field observations, two prominent sets of lineament (NE-SW and NNW-SSE), besides less prominent E-W and N-S trending lineaments of tectonic origin have been observed in parts of Allahabad area. Pervasive and penetrative sub-vertical joint sets parallel to the macroscopic linear structures along with collapse structures possibly of neotectonic origin are also noted in the basement rock exposed to the SSW of Allahabad. The development of various meso- and macroscopic deformed structures, presence of collapse structure in the basement strata and the near orthogonal channel shift of axial rivers provide evidence of basement reactivation in parts of Allahabad area, Ganga plain in space and time.  相似文献   

17.
Remote sensing data pertaining to LANDSAT TM FCC of bands 2, 3 and 4 of 9th May 1991 and IRS-1A LISS II digital data of 3rd May 1991, have been utilized for the study of geomorphology of Bulandshahr district, U.P. Visual interpretation technique has been followed for geomorphological mapping and the area has been separated into four broadly defined geomorphic zones, namely Varahasi Older Alluvial Plain, Aligarh Older Alluvial Plain, Terrace Zone and Recent Flood Plains of Ganga and Yamuna, each characterized by its own geomorphic/landform elements discernable on remote sensing data. The Varanasi Older Alluvial Plain represents the oldest geomorphic surface occurring at highest tectonic level in the Gangetic plain. The Aligarh Older Alluvial Plain represents a palaeo-flood plain of a north flowing palaeo-drainage in the area. The Terrace zone represents the older flood plain of Ganga and its tributaries. The Recent Flood Plains of Ganga and Yamuna rivers, which get periodically inundated, constitute the youngest geomorphic surface in the study area. Digital image processing outputs, particularly ratio images have been found to be helpful in identifying certain geomorphic landforms (old/abandoned channels, scars etc.) due to greater contrast within ratio images.  相似文献   

18.
Karjan river is an important tributary of Narmada in Gujarat. Along with one of its own tributaries, called Terav it has carved a “meandering valley” across the block faulted rldge and valley Deccan Trap topography, south of Narmada. Karjan originates at Bardipada, which is much nearer to Tapti river than Narmada and in the initial stretches its channel is consequent to faults and fractures. However, before emerging on to the alluvial plain in north it has a sinuous valley. With confines of this valley the present stream channel wanders back and forth and has incised deep into various Deccan Trap flows. The geometry of such meanders shows that this is an symmetric meandering valley. The valley as such is an antecedent one in which the present stream channel is ur.derfit and ingrown. Natural fluvial processes, accelerated by dynamic rejuvenation of the area and wetter climatic phases during Pleistocene and Holocene seem to have carved this meandering valley and integrated the drainage.  相似文献   

19.
The Dibru river basin of Assam is investigated to examine the influence of active structure by applying an integrated study on geomorphology, morphotectonics, subsurface structure, Digital Elevation Model (DEM) using topographic map, IRS 1D LISS III, IRS P6 LISS III, SRTM, seismic and subsurface data. Seismic data reveals existence of an upwarp and an important fault in the basement around the central and eastern parts of the Dibru basin, respectively. The influence of these structures is well observed on all the younger formations inferring their active nature possibly till the Recent Period. Existence of fluvial anomalies, viz. annular drainage pattern, lineaments, abrupt changes in the direction of river course, beheaded stream and valley incision infer role of structural control on the fluvial features of this basin. Most commonly used indices for morphotectonic analysis, viz. basin elongation ratio (Re), transverse topographic symmetry (T), asymmetric factor (AF), valley floor width to valley height ratio (Vf) have been used to identify the evidences of active structures in the area. The values of Re indicated tectonically active, T indicated an asymmetric nature, AF indicated tilting and Vf indicated active incision in the Dibru basin. The DEM, profiles across the valley and superimposed longitudinal profiles of incised channel bed and valley shoulder of the Dibru clearly reveal valley incision by the river. Three large paleochannels located in different parts of the basin had their headwaters towards east at the common source, i.e. the Diyun river. These paleochannels had been resulted when their headwaters avulsed to create new rivers due to affect of the subsurface structures during Recent (or perhaps Neogene?) Period.  相似文献   

20.
Conventional techniques of monitoring both long-term and short-term changes in river morphology is time consuming and expensive. Remote sensing with its synoptic and temporal capability is an effective tool to study river metamorphosis. The present study is carried out in lower Ganga basin where Hooghly river is an important river contributing sediment to this vast fertile plain. A time series planform analysis is carried out between 1971 to 1991 period. Thematic maps generated from Landsat MSS and IRS-IA LLSS-I satellite data for 1986 and 1991 period respectively is compared with 1971 topographic maps. The migratory character of paleocourse of Hooghly river is deciphered through the paleochannels, oxbow takes and meander scars deciphered from satellite imagery. The shortterm river metamorphosis like cut-offs, bar migration and point bar accretion morphology are mapped and compared with 1971 topographic maps. The critical zone with respect to cut-offs and future channel migration are identified for river stabilization work.  相似文献   

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