Changes In River Morphology Research Articles

River morphology information system: A web cyberinfrastructure for advancing river morphology research

The study of river systems is challenged by the complexity and volume of data required to understand and predict river morphology changes. The River Morphology Information System (RIMORPHIS) addresses these challenges with an open-access web-based cyberinfrastructure for advanced river morphology research. Built on the National Hydrography Dataset Plus High Resolution, RIMORPHIS integrates publicly available bathymetry data and third-party resources into a cohesive database architecture for real-time use and analysis. The platform, structured around a PostgreSQL database with PostGIS extension, offers tools for geospatial visualization using Deck.GL, data analytics with Python-based geospatial processing, and eHydro Cross Section Surveys integration via API. By providing on-demand access to relevant datasets and tools for data analytics and geospatial visualization, RIMORPHIS enhances data accessibility and interoperability, supporting informed decision-making in river basin management. This paper presents the development and functionalities of RIMORPHIS and its contributions to hydrological information systems as a self-sustained community platform.

Analyzing the association between the hydrodynamics and bank erosion along the Padma River: 2020 monsoon floods

The 2020 Monsoon floods submerged two-thirds of Bangladesh, profoundly affecting the stable char areas along the Padma River. This study addresses the under-explored link between Monsoonal flood hydrology and river morphological changes, introducing a novel approach that integrates one-dimensional steady flow hydraulic modeling, dual-sensor satellite imagery analysis (Sentinel-1 SAR and Sentinel-2 optical), and multiple machine learning techniques to assess flood impacts on bank erosion in the most affected reaches. Multiple linear regression (MLR), random forest (RF), artificial neural networks (ANN), and support vector machines (SVM) along with other statistical analyses, were employed to elucidate relationships between hydraulic variables and bank erosion. Results indicated a gradual decrease in river discharge-related variables from July to October, with peak erosion in July, primarily along the right banks and concave areas. In analyzing the relationships between hydraulic variables and bank erosion, the ANN model outperformed others, identifying flow area, stream power, and shear stress as the most influential predictors through importance analysis. This integrated approach offers a transferable framework for analyzing flood-induced bank erosion, enhancing riverbank erosion understanding crucial for flood risk management strategies in Bangladesh and similar river systems worldwide.

Changes in river morphology and influencing factors in the upper Yellow River over the past 25 years

Changes to the morphology of the upper Yellow River (UYR) had various impacts on the surrounding ecology and society, as well as the entire basin. However, low-spatial-resolution imagery (e.g., MODIS, AVHRR) cannot capture sufficient spatial details for monitoring complex water bodies, while high-spatial-resolution imagery (e.g., SPOT, Quickbird, Ikonos) lacks spatial coverage and the revisit frequency necessary for large-scale water body monitoring. To address these limitations, this study utilized the Google Earth Engine (GEE) and ArcGIS spatial analysis tools, applied pan-sharpening to downscale Landsat imagery of the study area from 1999 to 2023, performed river extraction, and calculated the spatiotemporal changes in river morphology in the UYR using river morphological parameters (i.e. area, channel width, centerline length, sinuosity index, lateral migration rate, channel stability). The Automated Water Extraction Index (AWEIsh) effectively characterized the study area, and pan-sharpening technology improved the extraction accuracy of small water bodies. Finally, the overall accuracy and Kappa coefficient were 0.993 and 0.985, respectively. Over the past 25 years, the area and average width of the entire reach of the UYR changed significantly, with the maximum value being 1.3 times the minimum value, whereas the centerline length and sinuosity index showed no apparent changes, and the lateral migration rate varied minimally, with the average annual movement ranging from 4.67 m to 10.18 m. In typical river segments without human activity, although single-channel reaches exhibited stronger stability than multi-channel reaches, natural factors (i.e. annual precipitation, annual runoff, annual sediment discharge) had a noticeable impact on the morphology of both single-channel and multi-channel reaches. Large-scale cascade hydropower development in the UYR has significantly impacted river morphology over a short period. Meanwhile, in river sections unaffected by human activities, the changes occurred gradually. This study provides support for better understanding complex river morphologies at large regional and long-term scales and a scientific basis for water resource management and sustainable development in the UYR.

Monitoring of River Morphological Change Using Remote Sensing and Hec-Ras in Lusi River, Indonesia

Changes in river flow have become a natural cycle of the river. The Lusi River has problems with meanders due to sediment transport, which is difficult to control. A combination of GIS with RS and HEC-RAS simulation was used to monitor river flow. The water monitoring method utilizes four water indices: NDWI, MNDWI, ANDWI, and SAVI, while the MPM-Toffaleti method is used for simulation. By combining the four methods, accuracy values of 0.68 to 0.92 and precision levels of 0.60 to 0.93 were obtained. MNDWI obtained quite high results compared to other indices. The results showed that the Lusi Riverexperienced quite extreme flow changes. Two flow cuts occurred. Considerable erosion occurred from 2003 to 2013 with a total lost area of 0.1943 km2, while from 2013 to 2023, there was erosion of 0.1177 km2. The HEC-RAS simulation of the Lusi River experienced erosion of 60 to 70.4 percent of the length of the stream. Changes in the riverbed in 2013 were found to be -1.1 ± 2.03 m, and then in 2023, the range of changes in the riverbed was -2.69 ± 1.29 m. Based on the results of the index and simulation of the Lusi River experiencing erosion in the flow, the level of erosion has increased every period.

Spatio-temporal analysis of riverbank changes using remote sensing and geographic information system

Fluvial hazards cause severe damage to human lives and properties. The increased intrusion of anthropogenic activities into natural hydrological cycles has increased hazard severity and confounded river channel dynamics. The present article studies the epochal channel erosion, accretion, and unaltered sites along the 42 km stretch between the Polavaram project and Dowleshwaram Barrage on the Godavari River. Geographic Information System (GIS) and Remote Sensing (RS) techniques were used to identify changes in river morphology. A total of five decades of Landsat images were analyzed, classifying the land use with a supervised learning Support Vector Machine (SVM) algorithm and an ISO cluster unsupervised algorithm to delineate the rivers and study the influence of land use land cover change (LULCC) on river morphology. Accretion and erosion channel changes during the assessment period were measured at all reaches, and the possible driving mechanisms of morphological alterations were studied.The results indicate the susceptibility of human dwellings and agricultural lands to floods due to the shifting of the highly vibrant river shoreline. The study provides the most recent information on Godavari River dynamics. These aspects of the river's evolution will aid in planning and management in the lower portions, which have not been well understood. River channel alterations can be quantitatively and economically analyzed using Remote Sensing (RS) and Geographic Information System (GIS) data.

River Morphological Change and Sedimentation Countermeasures Analysis in Miu River

One major floods problem in Miu River is huge amount of sediment which transported along the river channel. The decreasing of river capacity has been analysed and some channel courses changes also detected. These problems caused river morphological change and it is necessary to find comprehensive solution which not only decreasing the flood damage but also consider appropriate approach to natural environment. The complexity of these problems and possible solutions to overcome flood and sedimentation problem were investigated. Increasing of river capacity by channel excavation, protecting riverbank with revetment and construction of sediment control facilities were proposed as main solution. However, it is necessary to evaluate the effectiveness of these efforts by analysed sediment control facilities location and dimension of the structures. Some alternatives were investigated in order to find most effective solution to solve flood and sedimentation problem in Miu River.

Resilient spatial design strategies research of urban inland rivers: The case of Xinghai Lake wetland in Ningxia, China

Improving the resilience of rivers is a crucial method for mitigating urban flooding, restoring the ecological role of rivers, and promoting sustainable ecological development. This study specifically examines the relationship between changes in river morphology and river elasticity space, using the Xinghai Lake wetland as a case study. The MIKE 21 numerical model is employed to simulate and analyze the morphology changes of Xinghai Lake under various conditions during both the low-water and high-water periods. The findings indicated that during the period of abundant water, the inundation area of Xinghai Lake increased by 1.64 times, the average water level rose by 0.96 m, and the average flow speed decreased by approximately 11.8 % compared to the flat water period under the circulating condition within the lake. By utilizing Xinghai Lake as a channel for overflowing Yellow River water, the stability of the lake's body is improved. When Xinghai Lake is utilized as the channel for water from the Yellow River, it contributes to the increased stability of the lake. Based on the morphological characteristics of various river sections, this study identifies the potential areas for scouring, eutrophication, and flooding in the future. It also suggests specific strategic solutions to improve the resilience and ecological robustness of the river. These proposals aim to provide scientific support for enhancing the ecological robustness of urban inland lakes.

Quantifying Spatio-Temporal River Morphological Change and Its Consequences in the Vietnamese Mekong River Delta Using Remote Sensing and Geographical Information System Techniques

The evolution of delta and riverbank erosion within the river basin can significantly impact the environment, ecosystems, and lives of those residing along rivers. The Vietnamese Mekong Delta (VMD), counted among the world’s largest deltas, has undergone significant morphological alterations via natural processes and human activities. This research aims to examine these morphological alterations and their impacts on local economic and social conditions in the VMD. This study utilized satellite data from 1988 to 2020, coupled with population density and land use/land cover (LULC) maps from 2002, 2008, and 2015. The findings reveal that the VMD experienced widespread erosion over the past three decades, covering an area of 66.8 km2 and affecting 48% of the riverbank length (682 km). In contrast to riverbanks, islets showed an accretion trend with an additional area of 13.3 km2, resulting in a decrease in river width over the years. Riverbank and islet erosion has had a profound impact on the LULC, population, and economy of the provinces along the VMD. From 2002 to 2020, eight different land use types were affected, with agricultural land being the most severely eroded, constituting over 86% of the total lost land area (3235.47 ha). The consequences of land loss due to erosion affected 31,273 people and resulted in substantial economic damages estimated at VND 19,409.90 billion (USD 799.50 million) across nine provinces along the VMD. Notably, even though built-up land represented a relatively small portion of the affected area (6.58%), it accounted for the majority of the economic damage at 70.6% (USD 564.45 million). This study underscores the crucial role of satellite imagery and GIS in monitoring long-term morphological changes and assessing their primary impacts. Such analysis is essential for formulating effective plans and strategies for the sustainable management of river environments.

Reassessing the indicator value of the EPT group in karst rivers under hydromorphological pressure

Abstract Hydromorphological degradation is one of the most common stressors to freshwater ecosystems nowadays. Rivers lose riparian vegetation, habitat heterogeneity, natural flow velocity, etc., due to hydromorphological alterations. We analyzed macroinvertebrate communities in a wide range of hydromorphological conditions – from near natural sites to significantly altered water bodies, focusing on Ephemeroptera, Plecoptera, and Trichoptera (EPT). Considering that the EPT group is a quite sensitive and generally stenovalent group, we wanted to examine which of the hydromorphological pressures affects them the most. We also wanted to identify indicator taxa for different levels of degradation: minor, moderate, and severe. We collected samples from 84 karst rivers sites in Croatia. We found 52 taxa of EPT (Ephemeroptera – 21, Plecoptera – 11, Trichoptera – 20). Changes in river morphology proved to be the most important stressor affecting the distribution of the EPT group. Hydrological regulation did not show significance toward the EPT community, possibly due to the karst nature of the rivers studied. The most sensitive EPT taxa were those with the greatest preference for macrophytes and lithal habitats. More tolerant EPT taxa were those with a wide range of habitat preferences and/or taxa that feed on particulate organic matter.

Limitations in the use of Sentinel-1 data for morphological change detection in rivers

ABSTRACT The identification of morphological changes occurring along river channels is essential to support river process understanding, assess sediment budgets and evaluate the effectiveness of river management. Among available remote sensing techniques, space-borne synthetic aperture radar (SAR) could potentially provide a powerful complement to optical imagery for this task. However, very few studies have been carried out on the use of SAR datasets to study erosion and deposition processes in river channels. In this work, we investigate the potential of change detection analysis based on Sentinel-1 data, by comparing variations of radar backscattering to river morphology changes identified through high-resolution drone acquisitions. We considered a time series of two years of Sentinel-1 data relative to a period where, despite a moderate fluvial event occurred, morphological changes have been significantly detected in multitemporal drone point clouds. Satellite optical imagery (planet.com) and hydro-meteorological data were used to support the analysis and interpret results. The results show that the spatial and temporal resolution of Sentinel-1 is currently not suitable for accurate discrimination of morphological changes related to river dynamics at local scale. Other spaceborne sensors with sub-metric ground sampling distance and/or daily revisit time would be probably suitable; however, so far, this option would need the use of commercial solutions with a consistent increase of the costs of the investigation.

An Integrated Approach for Analyzing the Morphological Evolution of the Lower Reaches of the Minjiang River Based on Long-Term Remote Sensing Data

Understanding the evolution of river morphology is crucial for comprehending changes in water resources and implementing development projects along rivers. This study proposes an integrated approach utilizing remote sensing image data combined with deep learning and visual interpretation algorithms to analyze continuous-type changes in river morphology. This research focuses on the lower reaches of the Minjiang River in China and comprehensively analyzes the river’s morphological evolution from 1986 to 2021. The results show that the proposed method of river water identification in this study demonstrates high accuracy and effectiveness, with an F1 score and Kappa coefficient greater than 0.96 and 0.91, respectively. The morphology of the river channel remains stable in the upstream and estuarine sections of the study region while undergoing substantial alterations in the middle section. Additionally, this study also identifies several factors that significantly impact the evolution of river morphology, including reservoir construction, river sediment mining, river training measures, geological conditions, and large flood events. The findings of this study can provide some insights into the management and conservation of water resources.

Surrogate Method for Suspended Sediment Concentration Monitoring on the Alluvial Reach of the River Danube (Baja, Hungary)

Sediment balance is essential for understanding changes in river morphology and ecosystems and related services depending on them. However, the currently used methods to quantify riverine sediment processes are not adequate enough. We have examined the sediment regime of the Danube River, particularly the suspended sediment yield. This parameter can be calculated based on stage or discharge using a suspended sediment yield rating curve; however, the uncertainty of this method can reach even 150%. The suspended sediment yield of a section does not only depend on processes that take place in the riverbed; thus, it cannot be described by only one easily measurable parameter. An integrated surrogate method based on turbidity registration is tested in order to determine suspended sediment yield on the lower Hungarian (sand-bed alluvial) reach of the Danube River. The near-bank turbidity is converted into suspended sediment concentration and then into suspended sediment yield. The turbidity is measured with a built-in turbidity probe, while the suspended sediment yield is determined with traditional methods (discharge measurement, suspended sediment sampling, laboratory processing, and calculation). The traditional and integrated surrogate methods are compared based on the results of the measurements, and different aspect correlations are established between flow parameters, turbidity, and suspended load. The results achieved with the integrated method are promising, but more measurements are required in order to refine the relationships in a broader interval.

Multi-decadal changes in river morphology in an urbanizing watershed: Highland Creek, Toronto, Canada

Urban land development causes significant changes to river channel form and function. Outcomes are strongly conditioned by local circumstances although responses such as channel enlargement and incision are common but are highly variable in extent and detectability. Many case studies focus on small watersheds (or short reaches) and before-after conditions, and direct causation and temporal trajectories of change are not well known but often presumed to be a single step change and response. Well-documented examples in fully-urban, larger watersheds are rare, and rarer still are cases covering the full trajectory from pre-urban to fully urban land cover with accompanying data on the direct drivers of change such as discharge and stream power. Highland Creek, Toronto, has a drainage area of 102 km2 and between the early 1950s and 2000s underwent a land cover change from agricultural to completely urban in very low relief terrain with channels in narrow valleys incised locally into glacial sediments. Streamflow monitoring, land cover data and aerial photography over this seven-decade period, along with a calibrated runoff model and digital elevation data, give a complete picture over multiple epochs of the causes and changes in fluvial hydrology and geomorphology. The complete transformation of the flow regime, along with channel straightening and steepening, resulted in increases in average stream power (total and specific) of the order of ten and six times, respectively. The channel is now exceptionally energetic with maximum total and specific stream power for 2-year flood approaching 5000 Wm−1 and 300 Wm−2, respectively. The semi-alluvial and supply-limited character of the channels is also influential. Channel response is variable along the 20–25 km of channel measured and is notably different between the sub-watersheds, related to timing of development and its intersection with engineering intervention, and changing conceptions of the channel over time. In places the channel widened by a factor of four or five and changed from high sinuosity meanders to wide, bar-chute morphology, consistent with regime expectations for gravel-bed channels. In other places the process of urbanization has involved progressive engineering of the channel to convey stormwater (channelized), protect infrastructure and mitigate erosion, so that responses in these reaches are much more restricted and fluvial functions such as bend and bar development have been eliminated. Substantial channel transformation can be seen to have occurred episodically resulting from two major flood events as well as the increases in magnitude and frequency of peak flows, which limit post-flood recovery. Urbanization effects and consequences have developed gradually over a long period, rather than in a single urbanization step change, and they do not match simple models of channel evolution. In many ways urbanization of the river is ongoing, particularly in the form of geomorphically-referenced design of the channels as a response to damage from large floods and overall institutional watershed planning. The ongoing urbanization story of Highland Creek illustrates some extreme effects of urbanization as well as the complexity and contingency of response to the physical and institutional processes influencing the trajectory of urban river evolution.

Evaluation of the potential stranding risk for aquatic organisms according to long-term morphological changes and grain size in alpine rivers impacted by hydropeaking

Hydropeaking is one of the major hydropower-related disturbances of natural processes in river systems. The artificial flow fluctuations that are caused by the on-demand production of electricity are known for their severe impacts on aquatic ecosystems. These particularly affect those species and life stages that are not able to adjust their habitat selection to rapid up- and downramping rates. To date, the stranding risk has both experimentally and numerically mainly been investigated with variable hydropeaking graphs over stable river bathymetries. There is a lack of knowledge on how single, discrete peaking events vary concerning their impact on the stranding risk when the river morphology changes in the long-term perspective. The present study precisely addresses this knowledge gap by investigating morphological changes on the reach scale over a period of 20 years and the related variability of the lateral ramping velocity as a proxy for stranding risk. Two alpine gravel bed rivers impacted by hydropeaking over decades were tested by applying a one-dimensional and two-dimensional unsteady modelling approach. Both the Bregenzerach River and the Inn River exhibit alternating gravel bars on the reach scale. The results of the morphological development, however, showed different developments in the period 1995–2015. The Bregenzerach River displayed continuous aggradation (uplift of river bed) over the various selected submonitoring periods. In contrast, the Inn River showed continuous incision (erosion of river bed). The stranding risk exhibited high variability on a single cross-sectional basis. However, on the reach scale, no significant changes in stranding risk were calculated for either river reach. In addition, the impacts of river incision on the substrate composition were investigated. Here, in line with preceding studies, the results show that the coarsening of substrate increases the stranding risk and that especially the d90 (90 % finer of the grain size distribution) must be considered. The present study reveals that the quantified stranding risk of aquatic organisms is a function of the general morphological (bar) characteristics of the impacted river and both the morphological and grain size development have an impact on the potential stranding risk of aquatic organisms and should be considered in the revision of licences in the management of multi-stressed river systems.

Study effect of slope change on sediment transport in the Dujila irrigation canal


 One of the main elements influencing the Dujila River's river shape is sediment. The characteristics of sediment supplied within reach when creating hydraulic constructions like a dam, irrigation canal, maybe even to use the stream for navigation purposes, would be one of the design engineer's main concerns.. The shallow depth brought on by riverbed aggradation may have an impact on the Dujila River's utilization as a source of drinking water and agricultural irrigation. Investigating sediment movement and the features of the river bed is essential to reducing the problems caused by River morphology changes. Utilizing the River Analysis System of the Hydrologic Engineering Center, a hydraulic examination of the transfer of sediment model was produced for this project (HEC-RAS). Along the Dujaili's 57 kilometers Information was gathered. The Manning coefficient was calculated for seven sections after calibration and verification. For 6 sections, samples from the river bed and suspended loads were taken in order to calculate the amount of silt. The model's output displays the pattern of river reach sections that follow erosion or deposition as well as the pattern of bed change. The model has been tested with various slope values to determine how slope affects sediment transport.

Spatial and temporal morphological changes in the lower Mekong River under the influence of sediment load reduction in the upstream

Due to the natural and anthropogenic activities, especially the rapid development of hydropower dams in the upper Langcang Mekong, the sediment flux in the lower Mekong has declined alarmingly. This factor is one of the main reasons causing the river morphological changes in the lower Mekong. In this study, we used the MIKE 21 model to simulate the spatial and temporal morphological changes of the Hau River crossing Tra Vinh and Soc Trang, Hau Giang, and a part of Can Tho and Vinh Long provinces of Vietnam, considering the impact of sediment load decrease from the upper boundary. The models were calibrated and validated using the data of the year 2017, and the scenario of a fifty percent reduction of sediment flux from upstream was considered. The results show that the erosion occurrence in the flood season is more significant compared to that in the dry season. However, the spatial distribution tendency of erosion and accretion was similar in the two seasons. Under the impact of reduced sediment load entering the investigated region, the spatial distributions of erosion and accretion locations were estimated to significantly change during dry and flood seasons. However, the riverbed change level changed apparently. The change is more considerable in the flood season; especially, the erosion was estimated to be more severe in all zone of the study area. The erosion level was estimated to increase up to 0.15m in the flood season in zone 1 compared to that under the historical condition. The accretion level increases up to 0.09m in zone 2 and 0.07m in zone 3 under flood season. The erosion level increases up to approximately 0.1m over six months of the dry season and flood season. The results of the study can contribute to the future management strategy for the local governments in particular and for the whole Mekong region in general.

River delta eco-morphodynamics under changing scenarios: The case of Lake Turkana, Kenya

In this work we explore the impact that changes in local climate and river hydrology have on the morphodynamics of a river delta, particularly focusing on the evolution of the delta generating at the lake inlet. We investigated the case of the delta in the lower reach of the Omo River in Ethiopia, which flows into lake Turkana, Kenya. The lake is the fourth largest lake and the largest desert lake in the world. This case study is of particular interest because within the last decades three dams have been built within the Omo basin. Among these, the Gibe III dam had a huge impact on the river hydrology and the sediment supply. To quantify changes in land use and river morphology and relate these to climate change and river hydrology we collated a historical dataset by combining information from different satellite sources. We observed that the amount of bare sediments progressively diminished and the biomass became denser compared to the existence of sparse biomass in the past. We argue that this is due to the changes in river hydrology and sediment load imposed by the dam, which increased sediment erosion by deepening the channel. The presence of the dam also increased the low flow level and reduced the peak flow during flood season, reducing the natural oscillations of the water table. In consequence, the possibility to plant for the local population was removed during floods. Our findings also indicate that the hydrology and reduced sediment discharge have changed the downstream (e.g. lake level), and upstream (e.g. mouth bar deposition) boundary conditions controlling the evolution of the delta structure, respectively. As a result, the delta morphology became less dynamic and less complex.

Monitoring and Modelling Morphological Changes in Rivers Using RS and GIS Techniques

River geomorphological investigation issues have received little attention in most countries of the world. Such processes become a pressing necessity due to climate change and anticipated events of extraordinary surges and dry seasons, which may debilitate the security of adjacent and downstream cities, particularly in locales that are exceedingly delicate and influenced by climatic changes. Al-Abbasia reach is a river that runs through the middle of the Euphrates River and is known for its numerous bends and meanders. The study of hydraulic structures such as barrages can provide important information about their influences on morphological processes in river reaches near the barrage upstream and downstream. Hydraulic analysis is made of the river behavior in u/s and d/s of hydraulic structures like barrages as a result of sediment deposition and erosion in u/s and d/s. A study, i.e., research on the impacts of the Abbassia barrage on the river system, has been conducted to address this issue using multi-temporal Landsat satellite data from 1976 to 2022 provided by the USGS. The study reach is located 5 kilometres upstream and 5 kilometres downstream of the Abbassia reach. Following the construction of the barrage, which had an impact on the sedimentation and geometry of the river, morphological variations took place in this part of the Al Abbassia reach. In this study, morphological changes throughout 49 years between 1976 and 2022 were investigated utilising remote sensing (RS) and geographic information system (GIS) approaches. Additionally, four image groups from three separate decades were used to perform change detection (1990–2000, 2000–2010, and 2010–2022). In this study, a monitoring system using Landsat-3 MSS: 1985, Landsat-5 TM: 1990, 1995, 2000, 2005, and Landsat-8 OLI: 2010, 2011, 2015, 2021, 2022 were employed to map river planform changes. The long-term comparison of this series of satellite images and historical maps for the period 1976–2022 indicates a continuation of change in the reach study with a rate of approximately 56, 33, 97, and 55% for upstream and 19%, 26%, 3%, and 45% for downstream for the width, area, deposition, and erosion, respectively. Furthermore, it is observed that there is a shift in river course within 200 m downstream of the barrage for the period of 1985–1990. The findings of this study, which monitor river morphological change at finer temporal and spatial resolutions, are crucial for promoting sustainable river management. They also aid in the investigation of river behaviour, which is necessary for providing the best management possible and overcoming the difficulties posed by this important research issue. Doi: 10.28991/CEJ-2023-09-03-03 Full Text: PDF

Setting the stage: How abrupt climate change, geomorphic thresholds, and drought control flood response in the lower Tennessee River, USA

Extreme floods, with multi-century to millennia recurrence intervals, arise from a combination of antecedent watershed characteristics and unusual or rare atmospheric circulations that occur too infrequently to discern drivers from instrumental records. Few stream gauge records in the United States contain 100 years or more of annual peak flow data, meaning rare extreme floods are underrepresented in the peak flow population. We synthesized approximately 8,000 years of paleoflood hydrologic data from multiple studies and various landforms (floodplains, rock shelters, and caves) conducted in the Tennessee River Valley between Chattanooga, Tennessee, and Florence, Alabama, to examine Holocene flood variability. Extreme floods (>11,000 m3/s) clustered around ∼7,900, 6,000–4,900, and ∼1,000–80 cal yrs BP. More moderate floods occurred between 4,800 and 2,000 cal yrs BP. We compared flood variability in the Tennessee Valley to Holocene paleorecords available in North America. All periods of extreme flooding occurred during large-scale, abrupt climate transitions that lacked a distinct directionality of temperature change (i.e., warm to cool or cool to warm). Our findings indicate that extreme floods clustered in times when (1) warm-season precipitation increased, (2) abrupt increases in precipitation followed episodes of drought, and (3) the rate of change in the hydroclimate regimes was greater than the rate of morphological change in response to increased moisture, thus, exceeded geomorphic thresholds. Internal river basin factors such as drought-induced watershed changes and river morphological changes are key flood drivers that set the stage for flood response to changes in precipitation. Our findings suggest that anticipated changes to drought and precipitation intensity due to modern climate change may increase extreme floods, particularly for urban and regulated rivers not given the space for adjusting to higher precipitation variability.

Assessment of river morphology based on changes in land use and land cover and the spatial and temporal variation of meandering parameters of the barak river

Abstract River morphology describes a river's cross-sectional shape, sedimentation, and erosion. The meandering parameters, oxbow formation and decadal land usage land cover (LULC) fluctuations of Barak River were investigated using 21 meandering spans to measure river morphological changes. The decadal meandering parameters were calculated reach-wise and section-wise to characterize river morphological changes. It was observed from the paired t-test that the river width significantly changed during the study period (1990–2020). Strong inter-relationships between the meandering parameters are shown from the regression analysis. The morphological investigation found a reduction in the centerline distance due to variations in the radius of curvature caused by the internal arc's reduction. As a result, the average sinuosity has decreased over time. The current work used SVM and ML techniques for LULC classification, and a comparison of ML and SVM techniques was also done. The SVM technique performs better. The decadal LULC analysis suggests that between 1990 and 2020, the areas of water bodies, forests, and bare land types declined. Whereas, agricultural and settlement areas increased. River morphology is substantially impacted by agriculture and urbanization, particularly in areas where oxbows occur simultaneously, since this work may apply to other similar meandering river management along the alluvial flood plain.