River Migration Research Articles

Environmental factors influencing annual sucker (Catostomus sp.) migration into a Great Lakes tributary

Fish migration in rivers is a growing area of concern as mounting anthropogenic influences, particularly fragmentation from dams and barriers, constitute major threats to global river species diversity. Barriers can impede the movement of fishes between areas critical to the completion of their lifecycle, affecting both population and ecosystem viability. In response, fish passage solutions have been identified as a critical need to maintain fisheries viability in the Laurentian Great Lakes, and around the world. Pivotal to the success of these fish passage solutions is a more complete understanding of the movement phenology and environmental cues that instigate migration. We used a dual-frequency identification sonar (DIDSON) to evaluate environmental triggers of river entry during spring and summer for three size classes of migratory fishes in the Boardman River, a Lake Michigan tributary. Our results indicate that medium size fish (>30 cm and < 50 cm), primarily composed of white sucker Catostomus commersonii and longnose sucker Catostomus catostomus were 21% more likely to enter the river at sunset and 25% less likely at midnight in comparison to midday. Entry rates of medium fish increased 6% for every 1 °C increase in river temperature, 4% for every 1 m3/s increase in river discharge from the day prior, and were reduced by 1% for every 10 cm increase in lake level. Understanding these processes in the tributaries of the Great Lakes is important to inform the fish passage solutions currently being developed for the Boardman River, and to inform management regulations for Great Lakes migratory fishes.

Aquatic ferns (Salviniaceae) in the Holocene sediments from the Bermejo River, Eastern Chaco, Argentina

The Gran Chaco Americano is a large subtropical plain and one of the major biogeographic and morphostructural territories of South-America. Eastern Chaco is the wettest sector of the Gran Chaco and has heterogeneous environments. It includes different types of woodlands and forests together with savannahs, grasslands and wetlands. These vegetation patterns have been proposed to be the result of the Quaternary alluvial plain dynamics and the intensive migration of the Chacoan main rivers. Fossil records-that show change-are scarce and most of them come from the Fidelidad Formation (late Holocene). This Formation is located on the Bermejo River natural levees near the Villa Escolar Town (Formosa Province, Argentina). Fern fossils discovered in this Formation correspond to heterosporous aquatic ferns (Salviniaceae). The impressions were assigned to Salvinia cf. minima Baker 1886. These correspond with orbicular to elliptical leaves, with a smooth margin, and both the apex and the base are rounded. The base bears a slightly developed petiole. The venation pattern is dichotomous with anastomoses forming areolas. Generally, four tubercles (trichome bases) per areola are observed. The massulae and spores correspond to Azolla cristata Kaulfuss 1824. The massulae are rounded, oval or kidney-shaped and have septate glochidia. Spores are trilete and spheroidal. The floating ferns Salvinia and Azolla are good indicators of open fresh-water or wetlands paleo-environments. Hence, the lower levels of the Fidelidad Formation are associated with mostly calm freshwater bodies such as rivers, streams or wetlands, which are closely related to the activity of the Bermejo River during the late Holocene. These aquatic fern fossils provide new insights into paleoenvironmental conditions and increase the paleontological richness of the Eastern Chaco.

The interaction processes of the fish assemblages between the Yangtze River and Poyang Lake, China

AbstractLateral hydrological connectivity (LHC) maintains the high biodiversity and ecosystem functions in the river–floodplain system. We investigated the changes in the taxonomic and functional composition of fish assemblages in the lateral connection channel between the Yangtze River and Poyang Lake, China, during the dry and wet seasons and which factors drive the changes. The results indicated more lake‐residence species and fewer river–lake species in the channel during the wet season than the dry season, leading to significant seasonal differences in taxonomic compositions and trait patterns. Water temperature, water level and fish migration influenced fish assemblage structures in the channel. Water‐level fluctuations that limited food sources and suitable habitats promoted the migration of riverine and lake‐residence fish during both seasons. Water temperature and level also significantly influenced species‐specific migration. Water temperature influenced the spawning migration of river–lake fish during the wet season. Based on these results, we found temporal species‐specific migration dynamics in fish assemblages in the lateral channel that were related to species’ life‐history traits. Therefore, we inferred that the temporal–spatial interaction of the fish community in the river–floodplain system is essentially derived from the evolutionary adaption to the monsoon climate. This process is well studied and predictable, and can be beneficial for managing the river–floodplain systems. The invasion risk of the exotic species, including fish and macroinvertebrates, should be assessed before implementing LHC restoration.

Evaluating the Relationship Between Meander‐Bend Curvature, Sediment Supply, and Migration Rates

AbstractRiver meander migration plays a key role in the unsteady “conveyor belt” of sediment redistribution from source to sink areas. The ubiquity of river meandering is evident from remotely sensed imagery, which has allowed for long‐term, high‐resolution studies of river channel change and form‐process relationships. Empirical, experimental, and theoretical research approaches have described two distinct relationships between channel curvature and river channel migration rates. In this study, we employ a novel application of time‐series algorithms to calculate migration rates and channel curvature at sub‐meander bend length scales using 6 decades of aerial imagery spanning 205 km of the Minnesota River and Root River, Minnesota, USA. Results from the Minnesota River provide the first empirical evidence demonstrating how migration‐curvature relations break down for rivers with low sediment supply, which is supported by the Root River data set. This not only highlights the importance of sediment supply as a driver of river migration, but also supports a simple means to detect river reaches lacking sediment supply. Furthermore, results from both rivers demonstrate that sub‐meander bend measurement scales are most appropriate for studying channel migration rates and further indicate that a quasi‐linear relationship—rather than the more commonly inferred peaked relationship—exists between channel curvature and migration rates. The highest migration rates are associated with the highest measured channel curvatures in our data set, after accounting for a spatial lag of channel widths. These findings are consistent with flume experiments and empirical data across diverse geologic and climatic environments.

River channel migration and land-use/land-cover change for Padma River at Bangladesh: a RS- and GIS-based approach

This study has been carried out to evaluate the river shifting and assessment of related effect on the land-use/land-cover using geographic information system (GIS) and remote sensing (RS) techniques between 1955 and 2016 for Padma River at Bangladesh. Alluvium is eroding chronically due to the rushing stream flow; therefore, people of this region are poor and government loss national assets each year that reflects the direct effect on the economy. The standard topographical map of 1955 and satellite images of 1973, 1987, 1999, 2011 and 2016 were used in the study. Impact assessment on land use/land cover around 5 km from the stream centerline of 1973 was obtained. This studied has been carried out in three steps: (1) analyzed migration rate from 1955 to 1973; (2) analyzed migration rate from 1973 to 2016 and (3) assessed migration rate impact on land-use/land-cover change using GIS and RS techniques. Normalized difference of water index technique was used for identification of land and water boundary. The maximum likelihood supervised image classification was applied to detect the land-use/land-cover type and identify erosional impact with best accuracy. Results of long-term river channel migration showed that the land area is influencing with river erosion, settlement area is increasing, vegetation area is decreasing, but sand bar, water body and cultivated land area are oscillating. The satellite images were collected during winter and dry seasons (from November to January), when stream flow is limited for a lower amount of rainfall. Maximum erosion and management plan are critical for area at section 2 right bank 1955 to 1973. On the other hand, a minor improvement of embankment is necessary at section 2 because erosion occurs from 1973 to 1987, 1973 to 1999 and 1973 to 2011 at left bank; at section 4 because erosion occurs from 1973 to 2011 at right bank; and at section 5 because erosion occurs from 1955 to 1973 at left bank. New land developments occur at section 3 left bank from 1973 to 2016; without it, the maximum occurrence of accretion number was found from 1973 to 2016 at section 2 right bank, section 3 left bank, section 4 left bank, section 5 left bank that help for river bank management, large-scale planning to prevent flood and reduce the property loss.

Channel dynamics and geomorphological adjustments of Kaljani River in Himalayan foothills

Channel dynamics is a significant geomorphological process that involves the channel migration, erosion-deposition and meandering of an alluvial river channel within its floodplain region. This geomorphic process is often accelerated by climatic condition and human activities which changes this natural process to a quasi-natural hazard. Current research work tries to evaluate the changing behaviour or dynamic nature of alluvial channel by enlightening average length and shape migration. Finally, state of the art techniques in Arc GIS has been adopted to prepare the mouza (village) wise erosion-deposition map by considering highly fluctuating mouzas of the Kaljani River and its adjacent village at the Himalayan foothill region. The primary data source was a series of time-sequential Landsat data of the years 1972, 1980, 1987, 1993, 1998, 2002, 2008, 2013, and 2019 spanning 47 years. Furthermore, we divided total study time into eight groups i.e. 1972–1980, 1980–1987, 1987–1993, 1993–1998, 1998–2002, 2002–2008, 2008–2013, and 2013–2019 for better understanding. During the study period (1972–2019) the average length of migration of the Kaljani River was 742.05 m and the annual rate was 15.79 m/year. Within this time frame of 1972–2019, the shape area migration of the channel was 66.79 km2 and the annual rate was 1.42 km2/year. The total area of bank erosion from 1972 to 2019 equaled 62.74 km2, out of which, 30.07 km2 were on the right bank and 32.67 km2 were at the left bank. Present analysis helps to enhance the effectiveness of planning and management of land resources and ecological balances in these 45 adjacent Mouzas of the Kaljani River. Among the various important causes, tectonic activity, rainfall, floods, and human intervention especially constriction of the embankment along the Kaljani River are the most significant causes for this dynamic changes of River Kaljani. The results of this study therefore, can be used as an important indicator of the vulnerability of the Kaljani River and also provides information about geomorphological instabilities of the study area.

Riverbank erosion and migration inter-linkage: with special focus on Assam, India

BackgroundRiverbank erosion becomes a vulnerable phenomenon in the bank of the Brahmaputra river and its tributaries. Around 17 riverine districts of Assam are affected by riverbank erosion and lost a large plot of land. Due to riverbank erosion the victims’ loss their homestead and crop land as well as their survival strategy in the eroded areas. Moreover, farmers largely affected due to riverbank erosion as they loss their sources of income. This forces the farmer to migrate to another place for their survival. The paper examines the linkage between river bank erosion and migration based on secondary information.MethodTo examine the linkage, information collected from government published sources ‘Census of India’ and ‘Statistical handbook of Assam’. On the basis of the information, 10 indicators constructed from 26 variables and then factor analysis method applied to examine the linkage between riverbank erosion and migration.ResultsFour variables that are agricultural worker, industrial worker, cropped area and livestock population are loaded into the first factor, for which the first factor is labeled as the socio-economic indicator. In case of second factor the two variables i.e. Migrational Growth Index (MGI) and urban population are loaded. On the basis of the loaded variables this factor labeled as demographic indicator. In case of third factor also two variables are loaded that is, Natural Growth Index (NGI) and Literacy rate. The loaded variables indicate that both NGI and Literacy rate are positively related. Two variables are loaded in this fourth factor i.e. river bank eroded area and the district population growth. This factor labeled as environmental indicator on the basis of the variables loaded in this factor. The factor correlation matrix indicates the opposite relation between first and fourth factor.ConclusionThe results obtained from Factor component analysis reveals that the first and fourth factor component mainly established the linkage between riverbank erosion and migration. Besides this the component correlation matrix also reveals the inter-linkage between the variables. Thus we can say that there is positive relation between riverbank erosion and migration. However, it can be interpret that farmers mostly affected due to riverbank erosion and migrate more, because most of the inhabitants of the floodplain areas are the farmers.

Exceptionally high mortality of adult female salmon: a large-scale pattern and a conservation concern

In recent decades, the relative proportion of female sockeye salmon (Oncorhynchus nerka) on spawning grounds of several British Columbia populations has declined. Coincident with the decline has been large changes to oceanic, estuarine, and river migration environments. Over the past 30 years, numerous telemetry tracking and laboratory studies have examined mortality of adult Fraser River sockeye salmon during ocean and freshwater migrations. We reviewed 19 studies that provided 40 situations where male and female mortality could be directly compared. Female mortality averaged 2.1 times greater than that of males and up to eightfold higher. High female mortality was also evident in migrating coho salmon (Oncorhynchus kisutch) and Chinook salmon (Oncorhynchus tshawytscha) and for sockeye salmon in other systems. Female mortality was highest when migration conditions were challenging (e.g., high or turbulent flows, high temperatures, confinement, or handling) and towards end of river migration. We review mechanisms for differential mortality, including energy exhaustion, cardiac performance, physiological stress, and immune factors. Female-specific mortality will become even more pronounced in coming years as ocean and riverine conditions continue to change.

National-scale assessment of decadal river migration at critical bridge infrastructure in the Philippines

River migration represents a geomorphic hazard at sites of critical bridge infrastructure, particularly in rivers where migration rates are high, as in the tropics. In the Philippines, where exposure to flooding and geomorphic risk are considerable, the recent expansion of infrastructural developments warrants quantification of river migration in the vicinity of bridge assets. We analysed publicly available bridge inventory data from the Philippines Department of Public Works and Highways (DPWH) to complete multi-temporal geospatial analysis using three decades worth of Landsat satellite imagery in Google Earth Engine (GEE). For 74 large bridges, we calculated similarity coefficients and quantified changes in width for the active river channel (defined as the wetted channel and unvegetated alluvial deposits) over decadal and engineering (30-year) timescales. Monitoring revealed the diversity of river planform adjustment at bridges in the Philippines (including channel migration, contraction, expansion and avulsion). The mean Jaccard index over decadal (0.65) and engineering (0.50) timescales indicated considerable planform adjustment throughout the national-scale inventory. However, planform adjustment and morphological behaviour varied between bridges. For bridges with substantial planform adjustment, maximum active channel contraction and expansion was equal to 25% of the active channel width over decadal timescales. This magnitude of lateral adjustment is sufficient to imply the need for bridge design to accommodate channel dynamism. For other bridges, the planform remained stable and changes in channel width were limited. Fundamental differences in channel characteristics and morphological behaviours emerged between different valley confinement settings, and between rivers with different channel patterns, indicating the importance of the local geomorphic setting. We recommend satellite remote sensing as a low-cost approach to monitor river planform adjustment with large-scale planimetric changes detectable in Landsat products; these approaches can be applied to other critical infrastructure adjacent to rivers (e.g. road, rail, pipelines) and extended elsewhere to other dynamic riverine settings.

Recolonization of lake whitefish river spawning ecotypes and estimates of riverine larval production in Green Bay, Lake Michigan

Lake whitefish (Coregonus clupeaformis) within the waters of Green Bay, Lake Michigan have recently shown a substantial increase in abundance. Furthermore, after over 100 years of extirpation, adult lake whitefish are found spawning within major Wisconsin tributaries to Green Bay. Many knowledge gaps still exist with respect to the chronology of adult river migrations, including the physical characteristics of upstream habitats selected for reproduction and the extent of larval production by these riverine ecotypes. Here, we use hydroacoustic imaging along with egg and larval surveys to evaluate this novel riverine spawning in 2017 and 2018. Highest abundance of adults was observed in the month of November as temperatures declined below 8 °C. Spawning areas consisted of cobble substrates, and site-specific fish densities were primarily correlated with river flows between 0.3 and 1.0 m/s, with specific values varying by tributary and year. Locations of egg deposition mirrored areas of high observed fish densities. Larval production was documented on each tributary using active trawl ichthyoplankton sampling, and larvae were observed outmigrating to open water environments. We estimated tributaries produced 452,000 larvae in 2017 and 721,000 larvae in 2018. To our knowledge, this represents the first documentation of successful lake whitefish larval production from Green Bay tributaries and suggests tributary spawning populations contribute to the greater abundance of lake whitefish observed in recent years.

Restoring Dynamic Fluvial Processes in Urban Rivers: Learning from the Aire and Isar Rivers

In process-based restoration, the objective is not to create a complex river form directly; instead, interventions are intended to “prompt” the natural processes to restore such forms. The improvements in ecological conditions are actually made over time by flowing water during floods (using the stream’s energy), and by the growth of riparian vegetation (using incoming solar energy). On the Aire River in Geneva, ecological function was restored to a formerly canalized river by providing the river with an <i>espace de liberté</i>. A grid of channels cut into the valley bottom allowed the river to freely flood, erode its bed and banks, and deposit bars, creating complex surfaces on which riparian vegetation established to support the food web of the riverine ecosystem. The diamond-shaped bits of land left between these channels (“lozenges”) gradually erode and evolve as the river migrates, creating complex channel forms. The Isar River in Munich restoration involved adding coarse sediment load, creating erodible bed and banks in place of formerly rigid boundaries, expanding process space for river migration, erosion, and deposition, and increased human access to the river over 8 km. Since restoration, natural transport of sediment has resulted in deposition of gravel bars, whose forms evolve during floods, supporting diverse habitats. The Isar and Aire Rivers provide compelling examples of processbased restoration meeting 4 criteria for process-based restoration: space, energy, materials, and time. They demonstrate the possibilities of urban river restoration to achieve both ecological and social goals through restoration of fluvial process.

Inquiry and analysis on Yellow River's migration to north and cities' adaptation in the Northern Song Dynasty

Inquiry and analysis on Yellow River's migration to north and cities' adaptation in the Northern Song Dynasty

Geomorphic mapping and investigation of the uplifted piedmont zone between Haridwar and Kotdwar, Indo-Gangetic Plain, India

Active tectonics plays a crucial role in the landscape evolution at the decadal to thousand to million-year time scale. Datasets to examine landscape changes at a decadal scale are rare in the Indo-Gangetic Plain (IGP), which is one of the most dynamic areas in the Himalayan orogenic front. In this paper, we report decadal-scale landscape changes, which occurred in the last 40 years in the piedmont zone of the Haridwar – Kotdwar region due to an active blind fault in the IGP. The identification of tectono-morphic features in IGP is difficult to comprehend due to the combined effect of climatically induced sediment supply and tectonically driven subsurface deformation of alluvium sediments in the piedmont zone. We used various satellite imageries and aerial photographs available from 1970, to detect and map the changes in the flow pattern of rivers in the study area, which resulted due to gradient change. Using optical satellite imagery, geomorphic indices, and field investigation, we mapped various morpho-tectonic features in the piedmont zone. Due to uplift caused by upwarping, a topographic high of ~40 ​m is observed in the Malin Fan, which has led to the migration of the subparallel rivers emerging from the Sub-Himalaya. We report an eastward shift of ~8 ​km in a period of ~40 years by the Malin River; the Khoh River also migrated towards the east and the Sigadi Sot River migrated towards the west abandoning its paleo courses. We propose that the neotectonic deformation by the subsurface Najibabad Fault (NF) has caused an upwarp of the Malin alluvial fan in the western Ganga Plain. The Gradient Length Index (GLA) anomalies calculated for the major rivers in the study area also show a series of negative anomalies, which is in agreement with an upliftment zone in the IGP. Remote sensing and morphometric analysis identified the potential uplift zone ~5 ​km north of NF in the piedmont zone, which is supported by field studies. It is concluded that the slip along NF will be essential to understand the evolution of the piedmont zone, which is actively deforming and can be a potential seismic hazard zone in the future.

Sedimentary records of mid-Holocene coastal flooding at a Neolithic site on the southeast plain of Hangzhou Bay, east China

The history and underlying mechanisms of extreme typhoon events during the Holocene on the east China coast are poorly resolved. This study presents an analysis of the chronology, sedimentology, and organic and alkaline-earth metal geochemistry of a profile (T0103W) collected from the Neolithic Xiawangdu site on the Ningbo Plain, east China coast. Through comparison with the chronology and palaeontology of a second profile from the same site, a coastal, tidally influenced fluvial setting is identified as the geomorphological environment which formed at ~5600 cal. yr BP in the context of a stable or falling relative sea level. Infilling or lateral migration of the tidal river occurred along with the outbuilding of the coastal alluvial plain during the Neolithic occupation. Two periods of salinity intrusion are identified, at ~5310–5145 and 4575–4330 cal. yr BP respectively, as indicated by the increase in Sr concentration and Sr/Ba ratios. Based on our multiproxy analysis, we suggest that frequent extreme typhoon events occurred during both periods. In response to the flooding, the Neolithic people either abandoned the low-lying land close to the river channel or retreated to dwellings constructed on earth mounds. The reconstructed history of extreme typhoon incursions on the east China coast is distinct from those of the South China Sea and southwestern Japan and reflects the complexity of typhoon tracks in the northwest Pacific basin in response to fluctuating sea level and climate change.

Vicissitudes experienced by the oldest urban center in Bangladesh in relation to the migration of the Brahmaputra River

ABSTRACTBangladesh is one of the most densely populated countries in the world. There are 57 trans‐frontier rivers in the country, the widest being the Brahmaputra River. The river's channels have frequently changed course, but the relationship between such river migrations and human settlement patterns has remained unstudied. In this paper, optically stimulated luminescence and radiocarbon dating techniques were applied to sedimentary and organic materials in the oldest urban center (Wari‐Bateshwar) in Bangladesh. The results showed that the landscape around the urban center was dominated by floodplain and peatland facies between 7.9–7.6 and 4.7–1.6 ka, respectively. Humans occupied this area at ~3.2 ka, and manufactured delicate semi‐precious gemstone beads between ~2.4 and 1.8 ka. The urban center might be the same as an important city of the Gangaridai described in historical records. Due to fluvial migration at ~1.8 ka, the area surrounding the urban center was covered by fluvial sand. Humans might have been forced to abandon the urban center, leading to the bead processing technology in Bangladesh being lost forever.

Changes in Morphometric Meander Parameters and Prediction of Meander Channel Migration for the Alluvial Part of the Barak River

Abstract A common phenomenon associated with the alluvial river is its meandering action which leads to lateral migration and thus geomorphic hazards. Predicting and preventing this migration is both difficult and necessary. Barak river is one of the highly meandering rivers flowing through the alluvial plains of Assam, India. It is observed that there is a regular shifting of the river banks and development of cutoffs which create uncertainty to the people residing nearby. Therefore, in this study planform geometry and migration behaviour of the Barak river is examined considering 12 representative meandering reaches using multiperiod Landsat remote sensing images, field investigations of channel bed and bank properties and riparian vegetation cover. An attempt is made to describe and evaluate the empirical approach and time sequence extrapolation method to predict channel migration. Channel wavelength to channel width ratio ranges between 5.53 to 12.9, and the bend curvature ranges between 1.1 to 3.93. Rate of river migration varies between 0.54to 85.69 m/year. Sinuosity in most of the meandering reaches is greater than 1.5. Results show that lack of significant riparian vegetative cover, high precipitation and presence of fine sands with very low clay content are probably the main elements responsible for the planform changes. The results of the prediction of meander migration obtained from selected empirical methods show that only Nanson and Hickin method shows a moderate correlation with R2 =0.50. Time sequence extrapolation method was used to predict the radius of the best-fit circle for the year 2025 and 2030. Results of the time sequence extrapolation method indicate that the maximum and minimum radius of the best circle fit for the year 2025 is 1254m at reach-8 and 462m at reach-7 respectively, and maximum and minimum radius of the best circle fit for the year 2030 is 1319m at reach-8 and 387m at reach-12 respectively. It is believed that the outcomes of this study could form a base in river training works and in understanding and predicting the future dynamics and bank migration of this alluvial river and other river of similar geomorphic setting.

ZAB RIVER (IRAQ) SINUOSITY AND MEANDERING ANALYSIS BASED ON THE REMOTE SENSING DATA

Abstract. This work studies the meandering and change of paths along the Zab River in Iraq. Landsat-5 TM, Landsat-7 ETM+ and Landsat-8 (2-sets) images were acquired from the years 1989, 1999, 2015 and 2019, respectively, which were used together with Remote sensing and Geographic Information Systems (GIS) techniques to study the changes. To determine the river/stream shape, the Sinuosity Index was calculated to classify Zab River segments into either the straight, sinuous or meandering class. Our findings via image analysis show coarse river migration and that most river segments fall into the two classes of sinuous and meander. In addition, it seems that the east bank of the Zab River region of the basin has extremely shifted where the river passes near the Kirkuk governorate.

Vulnerability of the biota in riverine and seasonally flooded habitats to damming of Amazonian rivers

AbstractThe extent and intensity of impacts of multiple new dams in the Amazon basin on specific biological groups are potentially large, but still uncertain and need to be better understood.It is known that river disruption and regulation by dams may affect sediment supplies, river channel migration, floodplain dynamics, and, as a major adverse consequence, are likely to decrease or even suppress ecological connectivity among populations of aquatic organisms and organisms dependent upon seasonally flooded environments.This article complements our previous results by assessing the relationships between dams, our Dam Environmental Vulnerability Index (DEVI), and the biotic environments threatened by the effects of dams. Because of the cartographic representation of DEVI, it is a useful tool to compare the potential hydrophysical impacts of proposed dams in the Amazon basin with the spatial distribution of biological diversity. As the impact of Amazonian dams on the biota of both rivers and periodically flooded riparian environments is severe, DEVIs from different Amazonian tributary basins are contrasted with patterns of diversity and distribution of fish, flooded forest trees and bird species.There is a consistent relationship between higher DEVI values and the patterns of higher species richness and endemism in all three biological groups. An assessment of vulnerability at the scale of tributary basins, the assessment of biodiversity patterns related to DEVI, and the analysis of teleconnections at basin scale, demonstrate that recent construction of dams is affecting the biota of the Amazon basin.The evidence presented here predicts that, if currently planned dams are built without considering the balance between energy production and environmental conservation, their cumulative effects will increase drastically and represent a major threat to Amazonian biodiversity.

Estimation and prediction of the oscillation pattern of meandering geometry in a sub-catchment basin of Bhagirathi-Hooghly river, West Bengal, India

Meandering is the winding curve or bends in a river within the floodplain area. Though it is a natural process, it affects the populace by the resultant effect of lateral migration with bank erosion in the floodplain area. The present sub-catchment basin (Nabadwip–Kalyani stretch) of the Bhagirathi-Hooghly river is a vital lifeline of southern West Bengal, which offers adequate water for irrigation, industrialisation, and human habitation. This region is experiencing a favourable geomorphic change through river bank line changing with bank erosion and sinuous meandering. Illegal sand mining and monsoonal flood enhances the meandering process and triggers the reduction of settlement and cropland. The present study elaborates on the migration tendencies and meandering geometry of this zone and tries to predict the future river centerline position in a sinuous course. The study area is divided into 30 cross-sections, which reveals the increasing trend of lateral migration and erosion behaviour towards the eastward section of this region. The spatial and temporal shifting of river centerline and resultant migration observes and predicts through the migration coefficient approach (Hasegawa in Proceedings of the Hokkaido Branch, Japan Society of Civil Engineering, pp 197–202, 1977; Ikeda et al. in J Fluid Mech 112:363–377, 1981. https://doi.org/10.1017/S0022112081000451 ; Motta et al. in Geomorphology 163–164:10–25, 2012. https://doi.org/10.1016/j.geomorph.2011.06.036 ) by Arc GIS v 9.3.1. This model indicates the trend of channel width decreasing, with increasing near bank velocity in the crescent of meandering bend in future. The simulated and predicted centerline validates by positive linear relation (R2) and lowest RMSE value in few cross-sectional areas. The oscillation character of meander signifies the amount of discharge in the sub-catchment basin. The unpredictable behaviour of the migration shows a rapid change of meandering geometry through the increasing nature of bank erosion possibilities with peak discharge during monsoon. The study predicts future centerline of the meandering channel and the information on river migration, which will contribute to the plan on bank erosion and denote the vulnerable zonation.

The transition from meandering river delta to braided river delta: Depositional characteristics and controlling factors from the second member of Shanxi Formation to the eighth member of Lower Shihezi Formation in Southeastern Ordos Basin

The Ordos Basin, as one of the most petroliferous basins in China, hosts 12.9 billion tons of oil reserves and 15.2 trillion cubic meters of natural gas reserves. The extensive hydrocarbon exploration and production shows that the southeastern Ordos Basin contains considerable potential in the Shanxi Formation and Lower Shihezi Formation. In this study, cores, wireline logs, thin sections, and heavy minerals are employed to carry out research on classification of sequence stratigraphy, identification of sedimentary facies, reconstruction of palaeo‐geomorphology, analysis of sediment supply, palaeo‐climate, and accommodation space changes. The results indicate that palaeo‐geomorphology gradient tends to be steep, which results in increasing hydrodynamics and turns to be wide and flat which results in decreasing accommodation space. In addition, heavy mineral distribution reveals the direction of sediment supply which indicates provenance changes. The palaeo‐climate changes commonly cause differences in lithology associations, monsoon and vegetation properties. The differences in temperature and humidity result in different colours of lithology associations which indicate various sedimentary environments. The prevalence of monsoon assists in the preservation of fluvial delta by controlling lateral migration of rivers through affecting vegetation and lithology associations. The accommodation space variations control the development of fluvial delta and result in various depositional characteristics of fluvial delta. All these factors trigger the transition from meandering river delta to braided river delta. The reconstruction of the transition and analysis of controlling factors play an important role on understanding the sedimentary evolution of analogous reservoir successions.