River Channel Changes Research Articles

Using the Relative Elevation Models to delimit the floodplain level development: The case of the braided-wandering Belá River, Slovakia

Abstract The Belá River is a specific submountain river running through the Liptov Basin in the Slovak Carpathians. Its transformation from a braided to a braided-wandering system and degradation including incision of the river system has been observed since the middle of the 20th century. These processes have created a complex system of floodplains with development stages. For their identification, the Relative Elevation Model normalizing absolute floodplain elevation to the river channel changes has been established. Three models have been prepared, from the channel bottom and water level elevation gauge by GPS, and the water level elevation by LiDAR. Based on the resulting models, the floodplain was identified and delineated to an active or potentially active floodplain, to an inaccessible floodplain spread behind artificial structures, and to a perched floodplain beyond the reach of the river. Spatial statistics, including “Hot spot analysis” and “Cluster and outlier analysis” have been used to identify recent river floodplain formation from 1949 to 2018, caused by simplification and incision of the Belá River. The unique aspect and contribution of the research lies in implementing and comparing the Relative Elevation Models and linking them to floodplain age.

Numerical Simulation of River Channel Change in the Suspended Sediment-Dominated Downstream Reach of the Sangu River

This study aims to clarify the characteristics of the riverbed deformation, bank erosion, and channel changes in the lower Sangu River basin using a depth-averaged 2-D flow model where suspended sediment transport is dominant and its flow characteristics are influenced by active tides. A 45 km long area including the river mouth is computed using the 2-D model, and the results are compared with the observed channel changes. The computation results show that bed deformation and channel change are mainly caused during the ebb tide period of the spring tide particularly in an area of about 10 km from the river mouth. The detail study domain calculation results show that the flow concentration at the bend area causes the bed erosion there, and the eddy separated from the main stream causes the sediment deposition at the inner bank, while this eddy is not developed at the outer bank, resulting in the bank erosion there. Through these investigations, the characteristics and mechanisms of the morphodynamics in the lower Sangu River reach, particularly the potential of the combination of tides and floods to enhance riverbed deformations and the associated bank shifts, have been clarified.

Geochemical characteristics of the modern Yellow River Delta sediments and their response to evolution of the sedimentary environment

IntroductionSedimentary evolution and river channel changes of large river delta (e.g. Huang River, Changjiang River) in response to environmental changes have been one of the key issues in global change research.MethodsThis study reconstructed sedimentary environment changes in the modern Yellow River Delta (YRD), based on grain size and elemental chemical analysis of two short cores (YDC and YDG) from the southern region of the Qing 8 course delta of the modern YRD. ResultsThe results indicated that the cores YDC and YDG sediment were dominated by silt (58.47% and 67.6%, respectively) with varied grain-size variations and poor sediment sorting. The cores YDC and YDG sediments are both predominantly composed of the major element SiO2, and have an average content of 55.53% and 58.45%, respectively. The R-mode factor analysis showed the content of chemical substances of core sediments was controlled by three factors: grain size, sedimentary provenance, and marine sedimentary dynamics. DiscussionBefore the diversion of the Yellow River to the Qing 8 course in 1996, the two cores sediment were mainly sources from the Yellow River, and both cores were in the delta-front sedimentary environment under weak hydrodynamic conditions. After the Yellow River was diverted to the Qing 8 course, the cores YDC and YDG experienced significant erosion under the nearshore strong waves and tides. And then the sedimentary environment of the YRD changed from siltation to erosion. The results of the study would be helps to further our understanding of the changes in sediment grain size and geochemical element characteristics in the Yellow River estuary, and reveal the evolution of its sedimentary environment.

Human interventions alter morphodynamics of meandering channels: Insights from decadal to pre-industrial observations in the Yangtze River

Human activities, such as reservoir construction and bank revetment, significantly alter downstream flow and sediment regimes and river channel changes, impacting river ecosystem services. However, our understanding of how intense human activities affect morphodynamics of meandering channels in big river systems remains incomplete due to the lack of high-resolution in-situ data. Here, we use comprehensive data encompassing hydrology and sediment, historical channel maps, and high-resolution river bathymetry to investigate the evolution of meandering bends in the Middle Yangtze River (MYR) across three distinct phases: the natural period (1490–1975), the bank revetment period (1975–2002), and the post-dam period (2003–2018). The study revealed that, in the absence of human intervention, the meandering channels of the MYR naturally experienced inner bank deposition and outer bank erosion, largely governed by curvature-induced secondary flow patterns in flow and sediment transport mode. In 1975–2002, outer-bank revetments reduced erodibility, stabilizing outer banks, while inner banks continued to experience lateral and vertical deposition, causing a narrower and deeper channel hydraulic geometry. Conversely, meandering bends had exhibited an unusual pattern of ‘outer bank deposition and inner bank erosion’ in 2003–2018. Channel morphological changes characterized by channel incision and widening were driven by changes from erodible bank boundaries to solidified bank boundaries, substantial reduction in suspended sediment concentration, and an altered and extended effective flow range (10,000–25,000 m3/s). Our findings highlight that human interventions such as damming and bank revetments can alter the conventional erosion–deposition morphodynamics of meandering bends in large river systems, carrying vital implications for sustainable river management in the Anthropocene.

Assessing Riverbank Change Caused by Sand Mining and Waste Disposal Using Web-Based Volunteered Geographic Information

River water is one of the most important natural resources for economic development and environmental sustainability. However, river water systems are vulnerable in some of the densely populated regions across the globe. Intense sand mining and waste disposal can lead to river changes, loose foundations, and biodiversity loss. This study aims to develop a web-based geographic information system (GIS) platform to monitor river channel changes and their impacts on river environments due to sand mining and waste burial. The system integrates open-source software, Windows Server 2012, a web server, and PostgreSQL with PostGIS plugins for efficient mapping and storage of geospatial data and volunteered reporting of location events. Interferometric methods, including SNAP2STAMPS Automated Algorithm, persistent scatterer interferometry (PSI), small baseline subset (SBAS), and Snap software, were used to analyze spatial changes of subsidence from Sentinel-1 satellite data from 2021 to 2023 in the Gadar River in Oshnavieh, Iran. The results showed that the maximum subsidence at the riverbank was −10.1 cm due to sand mining, and the maximum uplift was 8.2 cm due to waste landfilling. The average subsidence was reported to be −5.1 cm. The results emphasize spatial analysis, showcasing material mining’s impact on subsidence trends and underscoring the significance of public participation in monitoring river health. Three parameters—completeness, correctness, and quality—were used to validate the system. Validation results showed completeness, correctness, and quality rates of 94.15%, 92.48%, and 86.63%, respectively.

Recent changes in riparian and floodplain vegetation in England and Wales and its geomorphic implications

AbstractRecent river studies in the United Kingdom have observed an increase in riparian vegetation and its potential impact on river channel change and sedimentation. Here, we quantify changes in floodplain and riparian vegetation during the first two decades of the 21st century along reaches of eight gravel‐bed rivers in England and Wales that exhibit varied active and stable, single and multi‐thread planforms. The analysis employs information drawn from open‐access sources including national LiDAR surveys and the photographic analysis of repeat aerial and satellite imagery. Most reaches show an increase in woody vegetation across their floodplains reflecting both natural colonisation and deliberate planting, and all but one of the reaches show an increase in woody riparian vegetation cover along their riverbanks. Of the six reaches that have exposed riverine sediments, five show a reduction in exposed sediment area as a result of vegetation encroachment. Contrasts in the rate, extent and location of riparian change were associated with the stability of the channel planform, with differences seen between stable and more active reaches. The significance of riparian woodland in promoting riverbank stability is demonstrated. Riparian vegetation development varies between river reaches, largely in response to differing rates of channel movement but also because of multiple and diverse local decisions regarding the management of in‐channel and channel‐adjacent vegetation by landowners rather than a single national policy. We consider the relevance of our findings and the value of remote monitoring for future river management interventions.

Водозаборное сооружение для целей орошения земель в горных условиях Северного Кавказа

Purpose: to develop a water intake structure for land reclamation purpose under the conditions of water withdrawal from mountainous natural water sources. Materials and methods. The paper is based on the theoretical analysis of the river hydrological and geological characteristics, which made it possible to calculate the minimum flow required for the stable operation of water intake structure and guaranteed water withdrawal during the growing seasons. The design parameters of the water intake structure were developed using the method of expert assessment with non-parametric statistics by comparing several dependent variables. Having determined the required qualities for a water intake structure, the design of a reclamation facility adapted for the conditions of the mountain and foothill zones of the North Caucasus was developed. Results. To achieve this goal, a static method for analyzing water intake structures was adapted, and statements with a factorial rating scale for expert assessment were developed. Kendall's concordance coefficient was 0.726, the data were consistent, the significance level P was less than 0.05, the differences between the factors were significant. The layer-by-layer latticed type of water intake structure has maximum efficiency. The design of a bottom-type water intake structure has been developed on the basis of the river hydrological regime and the method of water supply to the system. This type of structure demonstrates high efficiency in conditions of difficult terrain and unstable water source regimes during the growing seasons, ensuring stable water intake with minimal impact on the ecosystem. Conclusions. The proposed design of a water intake structure can be adapted to different types of water resources and their fluctuations, which makes it acceptable for mountainous areas with variable water levels in natural water sources. Minimal impact on the ecosystem is ensured by a high degree of water purification without significant changes in river channels.

Spatio-Temporal Shoreline Movement of the Afram River in Ghana: The Application of Endpoint Rate and Net Shoreline Movement

Shoreline change is a severe threat to life and property in wetland regions. Shoreline change analysis is critical for integrated wetland zone management and is accomplished through the field and aerial surveys. The Afram River is a significant source of water, food, and economic activity for Kwahu and its neighbouring communities and a form of funds for the residents. The shoreline, nevertheless, has been transforming because of erosion and accretion. This study examined a low-cost innovative approach using space-based peripheral visuals and metrics. Transects and data analysis for the riverbank were created using the Digital Shoreline Analysis System (DSAS) in the Spatial database. The study employed Landsat images from three historical years (2001, 2015 and 2022) across 22 years. End Point Rate (EPR) and Net Shoreline Movement (NSM) statistics in DSAS were used to determine the extent of change. Questionnaires and key informant interviews were administered to farmers, boat operators, fishermen, and older residents to learn more about the factors responsible for changes in shoreline position. According to the study, 24% of the shoreline erodes at a section, while 86% is stable. The survey's mean erosion rate is -0.24 m/yr, whereas the average accretion proportion is 27 m/yr. The ramifications of the Afram River channel change have affected the socio-economic livelihoods, including out-migration, farm loss and displacement of settlement. As a result, all organisations and participants responsible for these riverbanks should work together to prevent further damage and erosion of the shoreline line and its marine life and resources.

The cause and inspiration of the nonlinear impact of the Three Gorges Dam operation on stage-discharge relation in downstream channels

Evaluating the effects of dam operations on downstream hydrological regimes is crucial to cope with the threat of flood. Some channels in dammed rivers have experienced erosion and counterintuitive higher flood water levels. However, the impacts of dam-induced channel changes and dam-altered streamflow on downstream hydrological regimes have been less thoroughly evaluated. Herein, we integrated the Distributed Time Variant Gain Model and a proposed grey model to thoroughly decouple the effects of TGD-altered Yangtze River streamflow and TGD-induced river channel changes on the stage-discharge relation in Jingjiang reach of the middle Yangtze River basin, from 2003 to 2014. The stage-discharge relation in Jingjiang reach is presented by the relation between water level at Chenglingji station (Zcl) and discharge at Luoshan station (Qls). The results indicate that the TGD operation increases Zcl by 0.01 ∼ 0.06 m and 0.02 ∼ 0.48 m on average when Qls is below 12,000 and exceeds 24000 m3/s, respectively. However, the TGD operation decreases Zcl by 0.01 m on average when Qls is around 18000 m3/s. Hence, the TGD operation has a nonlinear impact on downstream stage-discharge curves, which results from the TGD interception of the release, water–sediment regulation of the TGD, and the erosion of the fine-grained channel. Given that the causes of the nonlinear impact are widespread, we speculated that the resulting changes in downstream stage-discharge curves influenced by the water–sediment regulation of dams in fine-grained rivers will be nonlinear and exhibit the hook curve. Meanwhile, the purposed grey model helps to evaluate the impacts of dam-induced river channel changes on downstream hydrological regimes in data-scarce rivers. Our work helps to thoroughly evaluate the impacts of dam operations on downstream hydrological regimes and the resulting flood threat.

A pioneering riparian community dominated by Nystroemiaceae gymnosperms from the Guadalupian (middle Permian) of China

A new fossil plant community is documented from the Upper Shihhotse Formation on the North China Block with an extremely unusual composition and diversity. Zircon U–Pb dating yields an age of 268.3 ± 2.3 Ma during the mid-Roadian to early Wordian stages of the Guadalupian. The community occurs in two beds and is dominated by fossils of the gymnosperm family Nystroemiaceae, which account for up to 99% of specimens recovered and comprise stems, branches, roots, ovuliferous complexes of Nystroemia pectiniformis and N. sp., and leaves of Chiropteris reniformis. The two different species of Nystroemia are distinguished on size and apical features of ovules, with N. pectiniformis having two apical bicornuate horns, whereas N. sp. has apical auricular extensions. Leaves of C. reniformis are megaphyllous and possess a long petiole and net venation. In the Cathaysian flora, different species of Nystroemiaceae are distinguished by features of their ovules and habit, but all bear leaves of C. reniformis which suggests evolutionary modularity and different rates of evolution between the ovules and leaves. Both N. pectiniformis and N. sp. are shown to have been short, uptight trees. Sedimentary evidence shows the community grew in a meandering fluvial setting with repeated river channel changes. Compared with contemporaneously diverse Cathaysian floral communities in the Upper Shihhotse Formation, the vegetation has a very restricted diversity and is a rare occurrence of a gymnosperm-dominated community. The Nystroemiaceae demonstrates an r-selective ecological strategy as pioneering plants adapted to living in unstable habitats and newly opened gaps in the riparian zone.

Analysis of River Channel Change Using Remote Sensing Images at Kelantan River Basin

This study presents the utilities of remote sensing technique for analysis of river channel change using remote sensing images at Kelantan River Basin. Understanding river channel change is a key component in developing ecologically friendly and long-term fluvial projects, as well as a way to reduce maintenance costs. The project's study and conclusions will aid in determining how to recognise probable morphological change in river channels. Remote sensing is one of the effective methods for water quality monitoring through image analysis of study area. These tools provide valid means of studying river channel changes. In this study, river channel changes are monitored and quantified by using remote sensing and GIS in Kelantan River. This study focus on four interval years between year 1988 until year 2021 by using Landsat satellite images of 30 m spatial resolution. Landsat Thematic Mapper (TM) 5 images of three different years which are 1988, 1999 and 2010, and Landsat 8 of OLI/TIRS year 2021 were compared. The quantity of accretion and erosion was assessed using parcel-based geoprocessing in a GIS system. The locations are labelled with the year they were created. The area of each year is changing by study period of time for all four interval years 1988, 1999, 2010, and 2021 for research area 1 and 2. The results prove that the river channel in Kelantan is altering, where between 1988 and 2021, the Kelantan River's course has changed significantly. The years 2010 to 2021 are the most severely affected by erosion as a result of the flood in 2014 on the Kelantan River.

Hierarchical Multiple-Point Geostatistical Modeling Method and Application Based on Braided River Reservoir Architecture

The Lower Shihezi Formation of the Daniudi gas field in the Ordos Basin is a typical reservoir of a braided river system in an alluvial plain, characterized by extensive braided river development, parallel development from the near source to the center of the basin, and frequent interweaving and cut stacking, as well as a complex deposition process that has seen frequent river channel changes. The braided river belt, braided channel, channel bar inside the river, and interlayer within the channel bar constitute a hierarchical and complicated architectural feature, which poses a great challenge to accurately characterize this type of reservoir for modeling. We proposed a hierarchical, level-by-level embedding, and progressive multiple-point geostatistical modeling strategy that is refined layer by layer according to a 5–3 level architectural unit hierarchy, with the modeling results of each level providing constraints for the next level modeling. The hierarchical geological model based on the combination of qualitative architectural anatomy and quantitative pre-architecture unit scale is critical in guiding the efficient development of the remaining gas in the braided river reservoir in Daniudi.

Mechanisms Controlling Water‐Level Variations in the Middle Yangtze River Following the Operation of the Three Gorges Dam

AbstractUnderstanding the mechanisms controlling downstream water‐level variations after the operation of the Three Gorges Dam is important for riverine flood and drought management. However, our quantitative understanding of the multiple controls of river morphology, vegetation, and floodplain resistance on water levels in the Middle Yangtze River (MYR) remains limited. Here, we analyze changes in river channels and floodplain resistance in the MYR using 450 cross‐sectional profiles as well as data on discharge, water levels, sediment, and satellite images from 2003 to 2015. Results show an overall decline in low‐flow water‐levels (at a given small discharge) due to severe incisions of low‐flow channels caused by a sharp reduction of ∼90% in sediment loads from 1950–2002 to 2003–2020. In contrast, high‐flow water‐levels (at a given large discharge) display minor changes. Our analysis shows that the notably increased floodplain resistance due to vegetation growth is likely the dominant factor elevating flood water‐levels, followed by riverbed coarsening and greater fluctuations in the river longitudinal profiles. Our findings further the understanding of downstream geomorphic response to dam operation and their impacts on water levels and have important implications for riverine flood management in dammed river systems.

Changes in River Channel Dynamics of the Satluj River, Punjab: Using a Geospatial Approach

Abstract River channel change is a dynamic process which involves erosion, accretion, lateral migration and changes in its width through the geomorphological process. Shifting of a river causes a direct impact on natural and manmade constructions which are located near the floodplain with consistent damage and devastation of the area. The objective of this study is to analyze the spatiotemporal variation along the Satluj river during the period 1990 to 2019 using Landsat TM, ETM+ and OLI satellite data. Spatiotemporal analysis of the river channel has been carried out to analyze the river channel change morphology, mid-line channel shifting and changes in surface water area of the Satluj river using twenty randomly distributed cross-sections (X1-X20). For surface water area change analysis, the satellite derived normalized difference water index (NDWI) has been used. The obtained results indicates that the river width increased by 0.033 km in overall cross-section (X1-X20) in the year 2019 as compared to the year 1990. Mid-line shifting of the river is mostly towards the left bank of the river. The maximum channel shifting of 1.364 km took place from Chak Bandala village in Jalandhar district to Madarpur village in Moga district between the years 1990 and 2019. However, the NDWI results indicate that the river surface area has been reduced by -90.33 km2 between the years 1990 and 2019. Additionally, the average shifting rate of the Satluj river during the period 1990 to 2019 is by 0.778 km.

The Variations and Influences of the Channel Centerline of the Zhenjiang-Yangzhou Reach of the Yangtze River Based on Archival and Contemporary Data Sets

The Zhenjiang-Yangzhou reach of the Yangtze River is located at the top of the Yangtze River Delta, which is one of the most dramatic changes in the lower reaches of the Yangtze River. The study on the migration characteristics of the channel centerline is crucial for a comprehensive understanding of the river channel changes in the Zhenjiang-Yangzhou reach. In this study, a detailed calculation method is proposed to extract the channel centerline of the Zhenjiang-Yangzhou reach by using old maps and remote sensing satellite map and decompose it into seven parts. The spatial and temporal changes of Net Shift Distance (NSD), Cumulative Moving Distance (CMD), Migration Rate of Channel Centerline (MRCC) and Linear Regression Change Rate of channel centerline (LRCR) from 1865 to 2019 on the cross-section scale are studied. The results show that: (1) from 1868 to 2019, the channel centerline of the Zhenjiang-Yangzhou reach kept shifting. The average net displacement distance of the section is 1103.47 m on the right bank, and the average cumulative displacement distance of the section is 2790.51 m. (2) According to the NSD and CMD data of each part, the long-term movement direction of the channel centerline is basically the same, and a small part of the channel centerline has periodic reverse swing. The probability of channel centerline moving right is about twice that of moving left. At the same time, some rivers have high erosion risk. (3) Through MRCC and LRCR data, the total number of channel centerline moving left and right is 156 and 329, respectively, and the erosion risk level of the near half of the shoreline is high. (4) The change of river boundary conditions and hydrodynamic force will affect the migration rate and direction of channel centerline. (5) This study proposes a method to extract channel centerline from a braided reach and study its changes, which can be applied to other similar reaches with a long history of human activities and high density. The results enrich people’s understanding of the long-term changes of a braided reach in the lower reaches of the Yangtze River and have certain guiding significance for river regulation, navigation safety, and revetment construction.

Paleovegetation and paleotemperature in North China during the mid-Holocene based on sedimentological and palynological evidence from Lake Baiyangdian

The North China Plain is climatically sensitive and is also noted as one of the principal regions in East Asia experiencing pronounced climatic warming. We reconstructed the paleoclimate and paleoenvironment of a lake site in North China Plain during the mid-Holocene warm period, in order to provide reference data for assessing possible futures changes in the ecological environment in the context of ongoing climate change. The reconstruction is based on the chronology, sedimentology and pollen assemblages of two sedimentary sequences from the Lake Baiyangdian area, which are used to determine the regional vegetation composition and paleotemperature of the hinterland of the North China Plain during the mid-Holocene. The results show that the extent and distribution of Lake Baiyangdian varied due to river channel changes, which also affected the sedimentary facies and the patterns of erosion and accumulation. The pollen assemblages from the lacustrine deposits are derived from the entire catchment of Lake Baiyangdian and they reflect regional patterns of climatic and environmental change. During the mid-Holocene, mixed broadleaf-coniferous forest dominated the western mountains and hills, intrazonal grassland developed on the alluvial fans, and lake-swamp-floodplain environments developed in the hinterland of the North China Plain. Statistical analysis of the modern distribution and climate thresholds of Ceratopteris were used to estimate the mean annual temperature (MAT) and mean January temperature (MJaT) of the Lake Baiyangdian area during the mid-Holocene, which were respectively 3.5 °C and 7.7 °C higher than today. Our findings provide a scientific basis for landscape reconstruction and paleoclimate modelling in North China. • Characteristics of sedimentary strata in Lake Baiyangdian area during the Holocene • Environmental implications of sedimentary pollen assemblages from Lake Baiyangdian • Regional vegetation composition of the Lake Baiyangdian area during the mid-Holocene • Estimates of the mid-Holocene paleotemperature in the hinterland of North China Plain

Impact of the Three Gorges Dam on riverbed scour and siltation of the middle reaches of the Yangtze River

AbstractThis study investigated the influence of the Three Gorges Dam (TGD) on the evolution of nearby channels in the Yangtze River (Changjiang River) system in order to better understand the environmental impact of large‐scale reservoir operations. From 2003 to 2017, the amounts of runoff and sediment transport in the Yangtze River were reduced by 3.3–14.5% and 67.8–92.7%, respectively, relative to 1955–2002 before the TGD was operational. Topographic measurements of the middle reaches (Yichang to Hukou) of the Yangtze River were analyzed from 1975 to 2017, during which time the cumulative erosion of the flood channel was 22.78 × 108 m3, and the dry channel accounted for 90.3% of the erosion. Following commissioning of the TGD, the scouring intensity of the sandy gravel section near the dam initially increased then decreased, whereas the scouring intensity of sandy sections away from the dam continued to increase. Beaches on convex banks of curved sections were scoured, and deep channels on concave banks became silted. In braided sections, the braids tended to shrink, and the diversion ratio of the main branch during dry seasons reduced, resulting in frequent branch alternation. Compared to changes in the downstream river channels of other large reservoirs worldwide, scouring from the TGD is extensive. The findings of this study are significant for river channel regulation and waterway planning in the Yangtze River and worldwide.

Forecasting riverine erosion hazards to electricity transmission towers under increasing flow magnitudes

Flooding and erosion will pose increasing challenges to urban settlements and critical infrastructure, such as roads and power grids in the future. Improved projections on the impact of climate change to critical infrastructure are essential to assist future planning. This paper uses hydro-sedimentary modelling to predict river erosion threats to electricity transmission infrastructure in an urbanised river valley under multiple increasing flow magnitude scenarios. We use a coupled hydrodynamic and landscape evolution model, CAESAR-Lisflood, to simulate river channel changes along a reach of the River Mersey, UK from the present day to 2050. A range of synthetic flow scenarios, based on recent hydrological records, was used in the model ranging from ‘no change’ up to a flow with 50% higher magnitude. The results revealed: (1) riverbank erosion will pose significant threats to several transmission towers located along the river, requiring intervention to avoid destabilisation by the moving channel; (2) the total area of floodplain erosion and deposition ≥ 0.5 m deep was positively related to increasing projected flow magnitudes. However, through running a ‘low’ and ‘high’ erosion version of the model, the simulations revealed these threats were most sensitive to the calibration of the erosion component of the model, illustrating the challenges and uncertainty in forecasting long-term river channel change; and (3) how long-term simulations can assist in adaptation planning for electricity transmission towers. Further reach- and catchment-scale modelling will be necessary to determine the timings of large floods more accurately, which produce the most significant erosion and deposition events, and to evaluate the efficacy of protections to transmission towers.

"무인항공기를 활용한 금강 하도내의 퇴적지형 변화 특성 연구: 공주보 개방 전·후를 중심으로"

In this study is aerial photos and UAV(Unmanned Aerial Vehicle) images were used to analyzed the characteristics of depositional landform changes in the Geum river channels before and after the opening gate of Gongju weir. Based on the depositional landform classification result, the main stream and the bare land occupied most of the area in all periods, and also found that the main stream, mid-channel island, and sand bar occupied a greater degree of area increase or decrease compared to other landforms in the classification items. As a result of analyzing the characteristics of depositional landform changes before and after the opening gate of Gongju weir, it is judged that the depositional landforms have changed due to the decreased water level of the Geum river after the opening of the weir, the summer rainy season and typhoons, river stabilization after the effluence of Daecheong dam, supply and deposition of river sediments and fixation of vegetation. The results derived from this study can be used as basic data for the study of river depositional landforms and the establishment of management and conservation plans for the landforms in river channels.

River channel changes through time and across space: Using three commonly available information sources to support river understanding and management in a national park

AbstractIn river landscapes subject to prolonged and high population pressure, the impact of human actions is usually so pervasive that re‐establishment of ‘natural’ river conditions is not possible. However, understanding the impacts of humans on river ecosystems is essential to identify how degradation of condition may be slowed or reversed and may also lead to the recognition that some human activities may be crucial for maintaining highly valued and sensitive river ecosystems. To achieve the necessary understanding for such judgements, it is essential to assemble, synthesize and analyse information on human actions, river environments and their interactions. In this paper, we focus on three commonly available information sources (historical records/archives, topographic and geomorphological maps, river habitat surveys) that can deliver relevant information over three timescales (centuries, decades, years). We illustrate the potential of these three data sources to assemble thematic and quantitative knowledge about how river systems function under a history of different human pressures and interventions, by exploring an example river landscape: the New Forest, southern England. We use this illustrative example for three reasons. First, for more than 1000 years, the New Forest has been affected by a complex range of land use and management practices which have heavily influenced the contemporary river landscape. Second, many of these human actions have degraded the landscape but others sustain highly valued landscape characteristics and ecosystems. Understanding the relative negative and positive impacts of different human actions is essential to understanding any river landscape with a long history of human use, and thus to designing balanced and appropriate management approaches. Third, in this special issue in memory of Professor Ken Gregory, we focus on an example landscape where he conducted research, allowing us to incorporate insights and data from his observations.