Typical Floodplain Research Articles

How can oak regeneration in the Leipzig Floodplain Forest be effectively supported by femel plantations? Application of a demographic forest model

Like many temperate floodplain forests in Europe, the Leipzig Floodplain Forest (LFF) has been impacted by anthropogenic disturbances, such as historical forestry practices and hydrological alterations. As a result, the forest's tree composition has changed, as evidenced by the declining abundance of typical floodplain species—like pedunculate oak (Quercus robur)—which play an important role in maintaining biodiversity. Notably, oak is not naturally regenerating in the mature forest, situating a need for management intervention to assist oak regeneration. One such management intervention is to plant oak in femels, i.e. small-scale clearings, or canopy gaps. However, it remains unclear whether small femels (<0.5 ha) can ensure effective oak regeneration. Moreover, city foresters aim at reaching 40 % average oak cover in the forest overstory by planting oaks in femels, but uncertainty remains regarding how much of the area would have to be planted with oaks per year to reach this goal.To explore these questions, we collected forest inventory data from oak femels ranging from 0.1 to 0.6 ha in size and compared oak density, size, growth, and mortality across femel sizes. Furthermore, we used the demographic Perfect Plasticity Approximation (PPA) model to simulate oak overstory cover over time under a femel management regime to assess the percentage of the forest area that should be planted with oaks per year accounting for different groundwater conditions. To parameterise the model, we used forest inventory data to quantify growth rates of oaks in the femels and growth, mortality, and recruitment rates of all common tree species in the Leipzig Floodplain Forest that may regenerate under the oak canopy over time.Oak density, size, growth, and mortality were similar across femel sizes, indicating that smaller femels are as effective as larger ones in promoting oak regeneration, while minimising the impact on the forest structure. To reach the foresters’ goal of 40 % average oak overstory cover, it is recommended that approximately 0.3 % of the hardwood floodplain forest area is planted with oaks each year, independent of the groundwater conditions. This study illustrates how ecological modeling can assist conservation planning in the context of forest management decision-making and these results may also be relevant for other European floodplain forests where oak regeneration requires support through active management to conserve long-standing biodiversity.

Prediction of Adaptability of Typical Vegetation Species in Flood Storage Areas under Future Climate Change: A Case in Hongze Lake FDZ, China

China experiences frequent heavy rainfall and flooding events, which have particularly increased in recent years. As flood storage zones (FDZs) play an important role in reducing disaster losses, their ecological restoration has been receiving widespread attention. Hongze Lake is an important flood discharge area in the Huaihe River Basin of China. Previous studies have preliminarily analyzed the protection of vegetation zones in the FDZ of this lake, but the future growth trend of typical vegetation in the area has not been considered as a basis for the precise protection of vegetation diversity and introductory cultivation of suitable species in the area. Taking the FDZ of Hongze Lake as an example, this study investigated the change trend of the suitability of typical vegetation species in the Hongze Lake FDZ based on future climate change and the distribution pattern of the suitable areas. To this end, the distribution of potentially suitable habitats of 20 typical vegetation species in the 2040s was predicted under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 climate scenarios using the latest Coupled Model Intercomparison Project CMIP6. The predicted distribution was compared with the current distribution of potentially suitable habitats. The results showed that the model integrating high-performance random forest, generalized linear model, boosted tree model, flexible discriminant analysis model, and generalized additive model had significantly higher TSS and AUC values than the individual models, and could effectively improve model accuracy. The high sensitivity of these 20 typical vegetation species to temperature and rainfall related factors reflects the climatic characteristics of the study area at the junction of subtropical monsoon climate and temperate monsoon climate. Under future climate scenarios, with reference to the current scenario of the 20 typical species, the suitability for Nelumbo nucifera Gaertn decreased, that for Iris pseudacorus L. increased in the western part of the study area but decreased in the eastern wetland and floodplain, and the suitability of the remaining 18 species increased. This study identified the trend of potential suitable habitat distribution and the shift in the suitability of various typical vegetation species in the floodplain of Hongze Lake. The findings are important for the future enhancement of vegetation habitat conservation and suitable planting in the study area, and have implications for the restoration and conservation of vegetation diversity in most typical floodplain areas.

Small stream floodplains have high conservation value for riparian carabid beetles but less for ground‐dwelling spiders

Abstract Floodplains along rivers and streams are characterised by a high habitat heterogeneity and a large biodiversity. However, floodplains are highly threatened by anthropogenic activities such as channelisation and bank enforcement of watercourses. While floodplains along rivers are well known for their importance for riparian biodiversity, the conservation value of floodplains along small streams is less understood. We studied carabid beetles (Coleoptera: Carabidae) and ground‐dwelling spiders (Arachnida: Aranea) along forested small streams (~ up to 5 m width) in Rhineland‐Palatinate (Germany). We investigated 16 pairs of floodplains (natural stream sites with shallow bank and regular flooding events) and controls (deeply cut stream sites without regular flooding), where we sampled carabid beetles and spiders at different distances to the stream bank (0, 5 and 10 m). We found that floodplains along small streams had contrasting value for carabid beetles and ground‐dwelling spiders. For carabid beetles, we observed several typical floodplain species and distinct species assemblages and 2.7 times more individuals across species of conservation concern in floodplain sites. Moreover, species richness and total number of individuals of carabid beetles were highest directly at the stream bank (0 m distance) of floodplains compared with the more distant locations, while the opposite was found for the control stream sites. The spider composition also differed between floodplains and control steam sites, but only one typical floodplain species was detected. Species richness and number of individuals in ground‐dwelling spiders were lower in floodplains than in control stream sites. We conclude that the conservation value of floodplains of small streams is taxa‐dependent and that they appear less relevant for ground‐dwelling spiders but provide important habitats for riparian carabid beetles.

Spatial modeling of air pollution in Kharkiv city

&#x0D; &#x0D; &#x0D; One of the most pressing problems facing cities, which negatively affects public health. There is a global practice of online monitoring of the content of pollutants in the air of settlements and informing the population about dangerous periods of increased pollution concentrations for certain categories of diseases and the population as a whole. It is also likely that one of the factors of pollution spread is the landscape differentiation of the city’s territory. The purpose of the study presented in this article is to develop statistical and cartographic models of the spatial distribution of air pollutants within the city of Kharkiv and to establish the relationship between the degree of air pollution and types of urban landscapes. Methods. Based on the analysis of the main methodological approaches and tasks of cartographic modeling of the spatial distribution of air pollution, the study substantiates the choice of the modeling method in this study; the features of a large city as an object of cartographic modeling of air pollution are assessed. Results. Based on the results of long-term monitoring by the Kharkiv Regional Center for Hydrometeorology, a statistical analysis of the results of the maximum and average content of pollutants in the atmosphere of Kharkiv was made and the spatial distribution of air pollution in Kharkiv (including (dust, carbon monoxide, nitrogen dioxide, sulfur dioxide, formaldehyde) was modeled, and patterns of pollution distribution were identified according to landscape types. Conclusions. In general, the spatial analysis of pollutant concentrations in the territories of Kharkiv showed that, in terms of maximum concentrations, the southeastern part of Kharkiv is most affected by carbon monoxide, nitrogen dioxide, and formaldehyde. The reason for this is the large area of industrial facilities. The northwestern part of the city has the highest concentrations of dust and sulfur dioxide. There is a lowering of the relief in the floodplain type of landscape and dense development. Intensive traffic and lowered relief (floodplain landscape) cause high average concentrations of dust, carbon monoxide, and sulfur dioxide in the southern part of the city. Nitrogen dioxide concentrations exceed the TLK in the northwest. The reason is the lowering of the relief on the outskirts of the city (floodplain landscape). The central part of the city has a high average concentration of formaldehyde. In general, a pattern of high concentrations of pollutants was found on the floodplains of the Lopan and Kharkiv rivers, with the lowest concentrations confined to watershed types of terrain between the Kharkiv and Lopan rivers and the Udy and Lopan rivers.&#x0D; &#x0D; &#x0D;

Mid-Miocene terrestrial carbon isotope shift driven by atmospheric CO2 in the Xining Basin, NE Tibetan Plateau

The Mid-Miocene Climatic Optimum (MMCO; ~17–15 Ma) was a relatively recent warming event unrelated to human activity that provides an ideal analogue for our global warming future. However, the terrestrial ecosystem response to the MMCO remains unclear because of limited records. Continuous sedimentation from the Tashan Borehole (TSB) in the Xining Basin, northeastern Tibetan Plateau (NETP) spans the entire MMCO, with dates of 18.5–13.5 Ma from high-resolution paleomagnetic studies. Here, we explore the organic carbon isotope (δ13CTOC) record of TSB to investigate the NETP terrestrial ecosystem response to the MMCO. The sediments are typical floodplain deposits with δ13CTOC values ranging from −28.03‰ to −25.16‰, indicating terrestrial C3 plants were the dominant NETP terrestrial vegetation during MMCO. Further, an obviously negative shift of 0.6‰ occurred in TSB δ13CTOC during ~17.6–14.2 Ma. TSB δ13CTOC values show the opposite trend to global benthic δ13C values, both in the long-term Monterey Excursion event and short-term carbon maxima events. Increased atmospheric CO2 during the MMCO enhanced the carbon isotope fractionation through photosynthesis by terrestrial plants and resulted in more 12C-enriched organic matter. Similar processes on a global scale subsequently accounted for part of the Monterey carbon isotope excursion. Therefore, in warm and humid conditions, the carbon isotope cycle of terrestrial C3 plants in the Xining Basin was mainly controlled by atmospheric CO2 concentration, with superimposition of effects of enhanced East Asian summer monsoon precipitation.

Reproductive Biology of Striped Snakehead (Channa striata, Bloch, 1793) in Floodplain of Lubuk Lampam, South Sumatra

Striped Snakehead (Channa striata) is one of the fish species inhabiting the flooded floodplain. Currently, the striped snakehead fish population in the Lubuk Lampam floodplain is undergoing a significant decline due to continuous and unregulated fishing activities. To prevent this population decline, there is a need for comprehensive efforts in managing their reproduction. The objective of this study was to investigate the reproductive behavior of striped snakehead fish in the floodplain of Lubuk Lampam, South Sumatra. The research spanned five months, from December 2022 to April 2023, and involved the collection of fish samples from four different floodplain types: river, lebung, lebak kumpei, and rawang. A total of 284 striped snakehead fish were examined, and measurements of length- weight and their reproductive biology were observed. The findings revealed that the sex ratio of striped snakehead fish was skewed toward females, with a ratio of 1:1.7 (females to males). The size at which female striped snakehead fish reach maturity was determined to be 28.5 cm, while male striped snakehead fish matured at 29.30 cm. The peak spawning season for striped snakehead fish occurred in December, coinciding with the rainy season. The spawning grounds for striped snakehead fish were predominantly located in the lebung station in the upper reaches of the Lubuk Lampam Floodplain. Striped Snakehead fish exhibited a partial spawning behavior. Furthermore, these fish demonstrated a relatively high reproductive potential, with fecundity ranging from 5,859 to 30,321 eggs.

Spatiotemporal heterogeneity of inundation pattern of floodplain lake wetlands and impact on wetland vegetation

The inundation pattern is an important ecohydrological indicator for studying floodplain lake wetlands, as it is the key factor affecting the wetland vegetation distribution patterns. Poyang Lake, the largest freshwater lake in China, is a typical floodplain lake wetland. This study presents a hydrodynamic model and vegetation survey of Poyang Lake, analyzed the spatiotemporal heterogeneity of the inundation pattern (inundation duration and depth), assessed the response patterns of wetland vegetation concerning the inundation pattern, and examined the impact of the proposed Poyang Lake Water Conservancy Hub (PLWCH) on the inundation pattern and wetland vegetation. The results revealed that the inundation pattern of Poyang Lake had significant spatial heterogeneity. Inundation pattern was found to have a significant impact on the vegetation succession. The response relationship between the distribution areas of different wetland vegetation types and inundation pattern was in accordance with the Gaussian curve, and the ecological threshold range of the Carex spp. community was the greatest. Owing to factors such as climate change and anthropogenic activities, the inundation pattern of Poyang Lake varied significantly since 2003, with the average inundation duration and average inundation depth decreasing by 15 d and 0.32 m, respectively. Consequently, the spatial distribution of wetland vegetation changed significantly, whereby the Carex spp., Polygonum criopolitanum, and Phalaris arundinacea communities extended down to the lower elevation zone. In the future, the PLWCH may result in increases in the inundation duration and depth, restrain the downward vegetation extension trend, and promote the vegetation to move to higher elevations similar to the status prior to 2003. These findings provide a detailed description of the spatiotemporal heterogeneity of the inundation pattern and the drivers of wetland vegetation distribution patterns in floodplain lake wetlands, serving as a scientific basis for conservation and restoration of these ecosystems.

Multi-source remote sensing data and image fusion technology reveal significant spatiotemporal heterogeneity of inundation dynamics in a typical large floodplain lake system

Study regionThe Poyang Lake, which is located on the south bank of the middle-lower Yangtze River basin. The lake is the largest freshwater lake in China, and also a typical floodplain lake in the world. Study focusThe spatiotemporal heterogeneity of inundation dynamics of large floodplain lake system has not been paid enough attention. Based on the reconstructed high spatial and temporal resolution inundation dataset using the image fusion model and multi-source remote sensing data, this study systematically analyzed the spatiotemporal heterogeneity of inundation dynamics in the Poyang Lake- floodplain system. New hydrological insights for the regionIt is found that within the same floodplain lake, the inundated area and inundation frequency in different regions of the lake (the main lake region and the adjacent floodplain region) can have asynchronous intra-annual fluctuation and opposite inter-annual change trend. This is highly related to the hydrological complexity of the lake: the relative impacts of catchment inflow and the Yangtze River varies in different regions across the lake. The stage-area relationship at the central station along the flow direction of the lake has the highest linear correlation, which might provide more accurate estimates of lake surface/volume. In addition, this study highlights the importance of reconstructed high spatial-temporal resolution of remote sensing data for the accurate assessment of inundation dynamics in floodplain lakes. All the results enrich the understanding of complex hydrological regime of large floodplain lakes and are valuable for the practice of water resources management and ecological conservation in such lakes.

Assessing the long-term impact of cascade hydropower development on the inundation patterns of floodplain wetlands

The inundation process of floodplain wetlands plays a crucial role in maintaining the balance of river ecosystems, which are highly sensitive to hydrological alteration. Nevertheless, the specific mechanisms through which these hydrological changes affect the inundation patterns of floodplain wetlands are still unclear. This study aimed to investigate the impact mechanism of cascade hydropower development on the inundation process of floodplain wetlands. Multitemporal remote sensing datasets and long-term hydrometeorological data series were utilized in this study. By employing the water appearance frequency (WAF) index, wetland hydrological stability assessment, and wavelet analysis, the inundation changes in floodplain wetlands and the underlying hydrological driving mechanisms were examined. The results revealed significant alterations in the inundation frequency of floodplain wetlands due to the construction of upstream dams. Specifically, the construction of the Danjiangkou and Wangfuzhou dams led to an increase in the total inundated area of Part A (16.09 km2) and Part B (76.93 km2), respectively. Conversely, the moderate frequency inundation zone in Part C decreased (26.7 km2) after the construction of the Cuijiaying Dam. The typical floodplain wetland 7 shifted from high to low (8.94 km2) stability after the construction of the Cuijiaying Dam. Furthermore, the cascade hydropower dam construction resulted in increased fluctuations in downstream water discharge. This study provides an effective approach to understanding the impact of cascade hydropower dams on the inundation process of floodplain wetlands.

Floodplain lake response to climate-nutrient-hydrological pressure revealed through phytoplankton community succession over the past century

In aquatic ecosystems, phytoplankton is a key primary producer that is highly sensitive to environmental change. Understanding ecological succession in lake phytoplankton community structure is important when tracking associated long-term environmental response. Such information can be used to develop a comprehensive management strategy under changing environment. This study reconstructs long-term (100 year scale) phytoplankton community succession from sediment pigments in a typical floodplain lake (Poyang Lake), revealing potential lacustrine ecosystem response mechanisms to climate-nutrition-hydrology factors. Results show that Poyang Lake’s algal community has undergone rapid growth, with diatoms increasing by 9.3%, cryptophytes increasing by 8.7%, and green algae decreasing by 26.3%. In Poyang Lake, the point of change in algal community succession occurred after 1965, representing a 5–15-year delayed response compared to lakes around the world, largely due to the coupled effects of the unique hydrological fluctuations and anthropogenic disturbances. Additionally, sediment pigments were also used to accurately track four atypical algal outbreaks in Poyang Lake (i.e., 1955, 1960–1975, 1984, and 2003). Our results emphasize the importance of hydrological conditions during ecological succession processes in floodplain lakes. Here, coupling effects between water levels and other relevant factors explained 20%–32% of algal community variation. Furthermore, results showed that Poyang Lake had previously evolved under environmental stresses of nutrients and climate conditions while currently evolving under multi-source coupling pressure (climate-nutrient-hydrology).

Individual Morphometric Characters and Productivity of &lt;i&gt;Plantago maxima&lt;/i&gt; (Plantaginaceae) in the South Siberia (Republic of Khakassia)

Abstract—Phytocoenotic and morphological features, as well as the productivity of the giant plantain (Plantago maxima Juss. ex Jacq.) in typical floodplain landscapes of southern Siberia were studied. The coenopopulations of P. maxima growing in natural and reclaimed areas of the Bely Iyus River valley in the Shirinsky and Ordzhonikidzevsky districts of the Republic of Khakassia were assessed. Under contrasting environmental conditions, in associations with significant share of P. maxima its productivity was 8.2 ± ± 0.58 kg × 102∕ha of air-dry, and 7.7 ± 0.54 kg × 102∕ha of oven dry aboveground phytomass. P. maxima share of the total phytomass varies from 5 to 15% in mesophytic associations with high species diversity on well-drained soils, and from 40 to 80% in xerophytic associations confined to mounds with sandy, sandy-gravelly or pebbly sandy soils. In P. maxima, the size and variability of vegetative organs increase in plants growing in more moist environments, while in drier habitats, the generative structures increase in the size and variability.

Chronological evolution of Holocene floodplain of river Raidak within the Himalayan foreland basin, India

The present study aims to investigate the evolution of river networks and floodplain geomorphological features of river Raidak within the dynamic Himalayan foreland basin regime over 65 year's timescale (1955–2020). High resolution satellite images and old maps have been used to prepare the floodplain geomorphological maps. Additionally, field verification technique has been adopted to improve the accuracy of floodplain landforms mapping. Sedimentary log analysis was conducted in order to identify the floodplain types and fluvial architectural elements in the floodplain. The nature of channel oscillation has been assessed using different parameters (channel length, channel width, sinuosity, bank line migration and erosion-accretion area). Results showed that progressive migration of meander bends and channel shifting on a recent past time-scale have resulted into many floodplain geomorphic features such as cut-offs, palaeochannel, backswamps, abandoned channel and meander scroll bar on Holocene floodplain surface. These floodplain landforms are more prominent on the middle and lower part of the floodplain. Numerical investigation showed variation in channel sinuosity of the middle and lower reach of river Raidak-I (1.85, 1.64 and 1.73 during the year 1955, 1987 and 2020 respectively) suggesting channel lengthening and shortening during different time period through mender development and cut-offs formation. Result also shows spatiotemporal variation in channel width and increasing trend of erosion-accretion area during the period 1987–2020. The sedimentary log analysis suggests non-cohesive medium energy (specific stream power varies between 10 and 300 Wm-2) floodplain of principal class B characterized with meandering and braided channel pattern, multiple sequence of Holocene sediments and existence of different floodplain landforms. Different natural processes (variable discharge, frequent floods, active tectonics, meander migration and channel shifting) and human interferences (channelization, mining activities, construction of cross-sectional structures and land use changes) have been responsible for evolution and morphological modification of Raidak river system and their floodplains.

Debris flow characteristics of the compound channels with vegetated floodplains

Compound cross-sections with vegetated floodplains are a common type of cross-section in debris-flow gullies. Floodplain vegetation participates in large-scale debris flow events and regulates debris-flow discharge. Extensive research has been conducted on the water flow characteristics of compound rivers. However, few studies have investigated the debris flow characteristics of compound channels in mountainous areas, particularly those of debris flow and flash flood inundation areas with vegetation. This study discusses the section characteristics of debris flow gullies with vegetated floodplains, gully evolution processes, and their influence on debris flow. The results show that the compound debris flow gully with a vegetated floodplain is formed in the gully from the mature stage to the old-mature stage. The compound sections are developed in flow areas with a gentle slope, which can be bilateral floodplain, unilateral floodplain, and multi-main gully floodplain types. Owing to the vegetation of the floodplain, the roughness of the channel increases, which makes the beach roughness coefficient much larger than that for the main channel. In the integrated Manning coefficient method, the error in resolving the flow velocity and discharge is large and cannot reflect the difference in velocities of the floodplain and main channel, therefore the sectional splitting method is most applicable. Influencing debris flow movement, limiting channel migration, and retaining debris flow to the main channel were the main contributions of the riparian forest zone.

Mapping typical floodplain wetlands using the improved D-UNet model

Mapping typical floodplain wetlands using the improved D-UNet model

Experimental and numerical model studies of dike-break induced flood processes over a typical floodplain domain

Experimental and numerical model studies of dike-break induced flood processes over a typical floodplain domain

Dry–wet seasonal variations of microbially mediated carbon metabolism in soils of a floodplain lake

AbstractSeasonal water level fluctuations in floodplain lakes are known to alter carbon transport, yet it is unclear how such changes affect microbially mediated carbon metabolism. Poyang Lake is a typical floodplain lake linked to the Yangtze River and is significantly affected by water level fluctuations. In this study, we examined the differences of soil organic matter (SOM) properties, bacterial communities and carbon metabolic functions between dry (March) and wet (August) seasons in lake centre, delta and floodplain from Poyang Lake. Generally, the SOM properties (quantity and quality) and microbially mediated carbon metabolism in the three types of sampling areas have undergone greater changes from dry to wet season than bacterial community. Structural equation modelling and variation partition analysis indicated that SOM properties contributed more in shaping the carbon metabolism of microorganisms than bacterial community structures, especially in lake centre. Dry–wet seasonal changes of microbially mediated carbon metabolism in lake centre were mainly affected by amide C=O1650 and aliphatic C‐H2850, 2924, while the delta and floodplain were mainly affected by aromatic C‐O1234. Furthermore, we also found that bacterial community composition could better explain the effects of seasonal hydrology on carbon metabolism, rather than the diversity and assembly processes. We highlight that studies on tightly coupled changes in SOM and microbially mediated carbon metabolism can enhance the understanding of soil carbon dynamics across the floodplain lake.

CURRENT SITUATION AND UNACCEPTABLE PROCESSES OF THE TRUBIZ WATER MANAGEMENT LANDSCAPE-TECHNICAL SYSTEM

The concepts of «anthropogenic center» and «micro-focal processes» are analyzed and based on them the concept of «water-based micro-center» – anthropogenic micro-center, which was formed within a landscape complex under the influence of anthropogenic water management. It is noted that such micro-centers include engineering and technical structures, main canals, a network of drainage or humidification canals, which are confined to the river-floodplain, less often above-floodplain, type of terrain. Purposeful changes in the landscape structure that occur during the construction of the reclamation network, and aimed, in this case, for the benefit of man, lead to the emergence of «usefulness» of unfavorable processes. First, there is a violation of the hydrological regime not only of the landscape complexes where the system itself is built, but also of adjacent landscapes as hydrodynamically interconnected areas. An example of such a system is the water management landscape-technical system built within the basin of the Trubizh River. The Trubizh water management landscape-technical system is one of the first and largest in Ukraine reclamation system of bilateral action, located in the northwestern part of the Dnieper lowlands, and covers parts of Kyiv and Chernihiv regions. The construction of this system has led to the emergence of new micro-focal processes occurring in anthropogenic landscape micro-foci (anthropogenic paradynamic relationships), and inadequate supervision of the system – to the development of destabilizing (negative) micro-focal processes affecting not only the system but also for the development of adjacent landscape complexes. A retrospective analysis of the transformation of natural landscape complexes into anthropogenic (change of floodplain type of terrain to canal-floodplain) is carried out. It is noted that micro-focal processes within water management landscape-technical systems can develop in natural-anthropogenic and anthropogenic directions. Depending on the dynamics of development, micro-focal processes are divided into four categories (stable, fading, aggressive and «pulsating»). «Pulsating» and aggressive micro-focal processes are analyzed, as they are clearly traced within the Trubizh reclamation system. Aggressive micro-focal processes are actively developing when the water management landscape-technical system is at the stage of «destruction» (no control unit), examples are lowered ponds, abandoned landscape-engineering systems and reclamation canals. Active development and constant expansion of its boundaries are characteristic of such processes. «Pulsating» micro-focal processes include those that develop under the influence of anthropogenic factors (reclamation system is at the stage of «origin» or functioning), so they can develop (expand their boundaries) or fade (reduce the area of distribution). The map of distribution of unfavorable micro-focal processes within the Trubizh water management landscape-technical system is concluded. Negative micro-focal processes are developing along the entire reclamation system. The emergence of these processes is due to three factors: 1) inadequate supervision of the reclamation system, or complete lack of control; 2) inexpediency of construction of an open lateral reclamation network on the whole section; 3) non-compliance with norms on plowing of lands around drainage canals, lack of protective afforestation.&#x0D; Key words: water management landscape-technical system, Trubizh River, micro-focal processes, rational nature management.

A first-order approximation of floodplain soil organic carbon stocks in a river network: The South Platte River, Colorado, USA as a case study

The lack of watershed-scale estimates of floodplain carbon stocks limits recognition of the important role of floodplains and river corridor restoration in efforts to enhance carbon sequestration. We use the South Platte River watershed of Colorado, USA as a case study to illustrate spatial patterns of, and controls on, floodplain carbon stocks at the watershed scale. This case study illustrates the disproportionate importance of floodplains for soil carbon stocks relative to adjacent uplands and provides an example of how spatially explicit data can be used to prioritize floodplain restoration with regard to carbon sequestration. We use the hydrogeomorphic floodplain tool GFPLAIN to delineate the extent of 100-year floodplains in the South Platte River watershed. We distinguish elevation bands for the steppe, montane, subalpine, and alpine zones. We also differentiate bead (floodplain width/channel width ≥ 5) and string (floodplain width/channel width < 5) reaches within the montane and subalpine zones. Drawing on prior, field-based measurements of organic carbon stock in downed, dead wood and soil in these floodplain types, we estimate total floodplain organic carbon stock based on median values of stock in different floodplain types and the spatial extent of these floodplain types. This estimate includes organic carbon stocks in lake and reservoir sediments in the watershed. Soil constitutes the greatest reservoir of floodplain carbon. The total estimated area of floodplain is 2916 km2, which is 4.3 % of the total watershed area of the South Platte River. Our preferred estimate is 42.7 Tg C stock (likely range of 39.1–42.7 Tg). This equates to 11.1 % of a previously estimated overall carbon stock (above and belowground biomass and soil organic carbon) in the entire watershed of 384 Tg C. Floodplains are thus disproportionately important, relative to their surface area, in storing organic carbon in this semiarid watershed. Field measurements of floodplain soil organic carbon stocks from across the globe indicate that this finding is not unique to this watershed, with implications for prioritizing floodplain management and restoration as a means of enhancing carbon sequestration.

Factors controlling floodplain sediment storage in two tropical upland river catchments in the Lake Tana basin, Ethiopia

Floodplain sediment storage is an important component of a catchment’s sediment budget. Here, we present the first quantification of floodplain sediment storage for tropical river catchments draining to Lake Tana, NW Ethiopia. The catchments are characterized by relatively gently sloping to flat lowlands towards the lake (1788 m a.s.l.) and steeper river reaches in the uplands towards Mount Guna (4120 m a.s.l.). Sediment storage for 65 homogeneous floodplain segments was estimated by combining information on floodplain spatial extent obtained through the field- and remote sensing-based approaches, with information on sediment thickness obtained through sediment coring and the analysis of river cut-banks. Extrapolation to the entire catchment was done making use of floodplain typology and following the classification scheme of Nanson and Croke (1992) and other floodplain properties and catchment-wide variables. The results showed average sediment storage of 284 Mg m−1 river length or 21,760 Mg ha−1 floodplain area for the Gumara and approx. 227 Mg m−1 river length or 16,909 Mg ha−1 floodplain area for the Rib River catchments. Total floodplain sediment storage at the catchments scale, above the upper gauging stations, amounts to 92.9 Mt and 35.5 Mt for the Gumara and Rib River catchments, respectively. At the scale of homogeneous floodplain segments, sediment storage is related to floodplain width, floodplain slope, upstream catchment area, the average slope of the upstream catchment area, sinuosity, and floodplain type. Overall, floodplain geomorphology largely controls sediment storage. Approx. 70 % of the sediment is stored in low-energy cohesive floodplains which only take up 11 % of the total river length in both catchments. For most of the total river and valley extent, where rivers are incised and have more energy, storage is limited. Comparing our findings with similar studies in temperate catchments of Europe and N-America showed that sediment storage in the Gumara and Rib Rivers is lower by approx. 1 order of magnitude, for similar-sized catchments.

The polygenetic floodplain of the Upper Paraná River

The mega-river functions differently from ordinary rivers and its floodplain is characterized by its magnitude, morphological complexity, and evolutionary history. This study analyzes the morphological and evolutionary characteristics of the Upper Paraná mega-river floodplain (Qm 13,000 m3 s−1), characterizing it as polygenetic owing to the various formative processes involved, many of which are no longer active and have extended since the end of the Pleistocene. The Upper Paraná floodplain is adjacent to the channel and in-channel on the large islands of its lower section. The 235 km study reach river has anabranching stretches that are separated by nodal sections. The analysis used satellite images, aerial photographs, 35 colors, and 52 absolute dates. Four types of floodplains were characterized: inherited, formed by processes and morphologies no longer active in the system; bayfill, formed by overflow deposits in flooded areas; crest-and-trough, by the annexation of lateral bars; and mixed, by the combination of the types above and association of the Paraná floodplain with its tributaries. Floodplain formation occurred in three phases. 1) At the end of the Pleistocene when the river developed a braided sand-gravel pattern under a dry climate. 2) It began at the Pleistocene-Holocene limit, when climatic improvement produced hydrological changes in the river leading to the vertical and lateral excavation of the old floodplain, generating a new channel and a sandy terrace 10 m above the current river level. The formation of the current floodplain began in this phase with the abandonment of the pioneer lake-islands. 3) It started with a small semi-arid event in the mid-Holocene until the present. The current floodplain and river hydrology were defined in this phase. Tectonic interventions for forming the floodplain are also addressed in the text. Considering its varied origin, the floodplain is polygenetic, implying a complex mosaic of environments whose connectivity relationships are still unknown. We believe that the concept of polygenetic floodplains presented in this study will help the understanding of hydrological and ecological functioning of the polygenetic floodplains of tropical mega-rivers.