Natural Riverbank Research Articles

Successional development of shrub-woody vegetation on natural river banks along certain watercourses in the Julian Alps and their foothills (western Slovenia and northeastern Italy)

Successional development of shrub-woody vegetation on natural river banks along certain watercourses in the Julian Alps and their foothills (western Slovenia and northeastern Italy)

Nesting habitat of the Brown-throated Martin Riparia paludicola mauritanica in Morocco

The Brown-throated Martin Riparia paludicola (subspecies mauritanica) of family Hirundinidae is endemic to Morocco and known for its ability to dig tunnels in earthen banks in which it nests. The nature of the sediment and the morphological features of the nest holes and riverbank habitat have not been thoroughly described across the species’ range in Morocco. Here, we present a qualitative and quantitative analysis of the textural characteristics of the sediment chosen by the martins in two successive breeding seasons, using a sample of 104 nests, which covered most of the species’ distribution range in Morocco. We also studied the surrounding landscape and morphological features of a total of 114 nests. Our observations show that besides nesting in natural riverbank habitat, the Brown-throated Martin can use both manmade embankments and substrates (even cement and concrete) to carry out a successful breeding cycle. This study provides important information on the nesting habitat of the Brown-throated Martin across Morocco. We believe that such descriptive work can help with the conservation of this Moroccan endemic by better targeting the right habitat to either protect or restore. The findings also include information useful to assist in creating new nesting sites for the species.

Diversity and distribution variation of urban spontaneous vegetation with distinct frequencies along river corridors in a fast-growing city

River corridors are vital to urban ecology, regulating climate and providing habitats for animals. Spontaneous plants naturally colonize various spaces therein, where they play important roles. Previous studies have explored many factors driving spontaneous plant diversity at the city scale and in specific habitats. However, we lack a holistic understanding of the diversity and distribution of variation of spontaneous vegetation that directly reflects the effects of urbanization. We conducted a field study of 1250 sample plots along river corridors in Chengdu, a fast-growing city in China, and the spontaneous plants in fifteen microhabitat types were surveyed. Diversity and distribution patterns were examined for species with distinct dispersal abilities. There was a far greater richness of occasional species compared to dominant and common species, but occasional species were markedly less abundant. Vacant lots and natural riverbanks harbored the most species, but revetment walls and lawns also supported a considerable number of species, especially in the city center. Species diversity among different urban areas was strongly related to microhabitat conditions. The proportions of dominant, common, and occasional species varied among communities. In communities on vacant lots of less urbanized areas, the richness of dominant species was greater, whereas in green spaces created by planted vegetation, occasional species were more diverse. Green space microenvironments are hospitable to some rare species. Urbanization and microhabitats have co-effects and thus ultimately determine diversity and distribution patterns. Such patterns, if linked to ecological and ornamental value, can provide a new perspective and nature-based solutions to urban rewilding and landscape design.

Response of Soil Fauna to the Shift in a Riparian Landscape along an Urban-Rural Habitat Gradient.

Urbanization is accelerating worldwide, resulting in drastic alterations of natural riverbanks, which seriously affects the ecological functions and services of riparian landscapes. Our understanding of how anthropogenic activities influence soil animal communities within riparian zones is scarce. The soil fauna represents an important biotic component of the soil ecosystem and greatly contributes to soil structure and fertility formation. We investigated the richness, abundance, diversity, and distribution of soil animal groups, including macro- and mesofauna, in different riparian landscapes along an urban–rural habitat gradient. In natural riparian zones with permeable revetments, the soil fauna was richest and most abundant, mainly because of the low levels of human disturbance and the more suitable habitat conditions. Different soil animal groups responded differently to revetment type and distance from the water flow. The hygrophilous soil mesofauna, requiring a more humid environment, was more sensitive to shifts in revetment types, the location on the riverbank, and the seasons. In summer, when precipitation in the study area was highest, the abundance of the hygrophilous soil mesofauna was significantly higher than in autumn. Distance from the water flow significantly affected the abundance of the hygrophilous soil mesofauna. Our results demonstrated that hygrophilous soil mesofauna can serve as a good indicator in riparian zones, reflecting the hydrological conditions. We also observed interactions between revetment type and distance from the water flow; the distance effect was stronger in the natural riparian zone with a permeable revetment type. Our results highlight the importance of anthropogenic effects on soil ecosystem processes and functions in riparian landscapes, and the necessity of protecting and retaining the natural riverbank and native vegetation patches in riparian landscape planning and construction.

Vegetation of natural and stabilized riverbanks and early effects of removal of bank fixation

AbstractThe majority of rivers in Europe has been dramatically altered in terms of their morphology and hydrology with severe consequences for the diversity and ecological functioning of the rivers and their floodplains. Consequently, an increasing number of river reaches has been restored over the past decades, often including the removal of bank fixation to reinitiate bank erosion and allowing for a rewidening of the rivers' cross‐section. However, monitoring in detail the effect of such a measure on riverine vegetation is scarce. Using a Before‐After‐Control‐Impact (BACI) design, we analysed the early changes of the vegetation 2 years after the removal of bank fixation at the Mulde River (central Germany). The results were compared with two types of control sites, representing a nonrestored as well as a natural riverbank that has never been fixed. We analysed differences in taxonomic and functional composition of the vegetation between bank types as well as community turnover after restoration. Two years after restoration, the vegetation differed clearly from the nonrestored sites. A substantial proportion of the community, especially the newly established species, became more similar to the natural bank community. Most importantly, spatiotemporal heterogeneity of the vegetation increased after removal of bank fixation, being an indicator for re‐established dynamic processes similar to the natural site. The presented data serve as a baseline for a long‐term monitoring and quantitative meta‐analysis of restoration effects.

Investigation on the Impact of Cementation Media Concentration on Properties of Biocement under Stimulation and Augmentation Approaches

Biomediated soil improvement has been established as a promising solution for improving soil engineering properties in the last decade. The primary factor determining the efficacy of biocementation is the material properties of the precipitated crystals, which are highly impacted by the concentration of cementation reagents. In the present study, the biocementation potential of specific microbes liable for the augmentation and stimulation approaches are investigated at different concentrations of cementation media (CM) ranging from 250 to 2,000 mM. An indigenous soil microbe (BS3) and a consortium (C), both obtained from a natural riverbank environment, are analyzed for their potential to improve the soil strength in comparison with the standard biocementing microbe Sporosarcina pasteurii (SP). The soil strength improvement is investigated by conducting the needle penetration test on the biocemented soil samples. Maximum needle penetration resistance was observed at 500 mM concentration of CM for all the microbes. The isolated soil microbe (BS3) exhibited 30% more penetration resistance than SP at the optimal concentration (500 mM) of CM. The needle penetration resistance decreased at the higher concentrations of CM. The biochemical properties of the microbes were evaluated via a laboratory shake-flask batch test to determine the potential reasons behind the variation in the penetration resistance. Their biochemical properties, including the urease activity, urea hydrolysis rate, calcium depletion rate, and carbonate precipitation potential are compared at different concentrations of CM. The findings revealed that the microbes respond distinctively to different concentrations of CM. A detailed microstructure analysis on the precipitated CaCO3 crystals suggested that the morphology, texture, and quantity are possibly the major strength influencing parameters. The present study unravels the potential reasons for the distinct responses of the augmentation and stimulation-inducing microbes at the different concentrations of CM.

Controlling erosion while fostering plant biodiversity: A comparison of riverbank stabilization techniques

Bioengineering techniques have been encouraged over “hard” civil engineering such as riprap for recovering naturalness on stabilized riverbanks, but their effectiveness in reproducing the plant species diversity and vegetation succession present on non-stabilized (natural) riverbanks has rarely been assessed. Here, we compared alpha and beta diversity and successional trajectories of plant communities along the vertical profile of natural (40 sites), bioengineered (51) and riprap (33) riverbanks, in 55 streams of the second- to seventh-order in the province of Quebec (eastern Canada). Richness of total, hydrochorous and native species was higher on natural riverbanks than on those stabilized by riprap techniques along all riverbank elevations (upper, middle and lower parts of the riverbank). Bioengineered sites showed intermediate values. Natural sites contributed most to beta diversity on the upper bank, riprap sites on the middle bank. Temporal changes in species richness were observed only on the upper and middle banks, with an increase on riprap sites and a decrease on bioengineered sites. Beta diversity was mainly stable through time. Plant composition on bioengineered sites converged to that on natural sites for all bioengineering techniques at all bank levels, whereas for ripraps it did so only on the lower bank. For all bioengineering techniques, plant succession was driven by increasing native and hydrochorous species at all bank levels. Bioengineering is an effective alternative to riprap on stabilized riverbanks that leads to plant diversity and succession that most resemble those on natural riverbanks.

The preliminary inventory of coseismic ground failures related to December 2020 – January 2021 Petrinja earthquake series

The most recent major earthquake series struck near Petrinja (December 29th 2020 M 6.2), and triggered extensive ground failures in the wider area of Petrinja, Sisak and Glina. Coseismic ground failures including subsidence dolines, liquefaction and landslides have been documented over a large area by various experts and teams. These data are stored in the newly created inventory, which is openly presented in this paper. This inventory is administered and updated by the Croatian Geological Survey, and will be available online via a Web Map Service (WMS) (www.hgi-cgs.hr). The aim of the inventory is to not only provide data for the development of susceptibility maps and more detailed exploration for possible remediation measures, but also to define the priorities for immediate action. The earthquake triggered the rapid development of dropout dolines which endanger the local populations of the villages of Mečenčani and Borojevići. This is still an ongoing process in the vicinity of the houses and therefore in-situ exploration started immediately. Liquefaction related to alluvial sediments of the Sava, Kupa and Glina rivers occurred almost exclusively in loose and pure sands, and was accompanied by sand boils, subsidence and lateral spreading. Liquefaction also presents a greater hazard because settlement of houses and river embankments occurred. Lateral spreading caused failures of river flood embankments and natural river banks. According to the data known to date, the majority of the coseismic landslides were reactivated with minor displacements. Despite that, it has been recognised that houses at the edge, or in landslide colluvium suffered greater damage than other houses located outside the landslide impact zone.

Nesting ecology and reuse of nest burrows by Bank Swallow (<i>Riparia riparia</i>) in southern Yukon

Bank Swallow (<i>Riparia riparia</i>) is a declining insectivorous bird that nests colonially in near-vertical surfaces, including natural banks along waterways as well as those created by industrial excavation. Several threats are likely contributing to the population decline, conservation measures have been recommended, and monitoring methods have been developed. However, little is known of this species in the extensive boreal portion of its breeding range. To assess whether recommendations developed in southern areas are likely to be effective in a more northerly region, we investigated aspects of the nesting ecology of Bank Swallow in southern Yukon during 2013–2017. Nesting activity occurred between 20 May and 21 August. We found an exceptional abundance of nest burrows in natural riverbanks along 46 km of the Yukon River near Whitehorse (326 burrows/km), but relatively low percent burrow occupancy in both natural and artificial habitats compared to studies from other regions. Year-to-year persistence of nest burrows and rates of reuse of burrows were high compared to other studies. We highlight the potential importance of the boreal region for recovery of Bank Swallow in Canada, and the importance of using region-specific estimates of percent occupancy when monitoring Bank Swallow using burrow counts. Further study is needed to determine whether unoccupied burrows contribute to nesting success, and whether there are situations in which Bank Swallow burrows should be protected year-round instead of only during nesting.

Assessing bank erosion hazards along large rivers in the Anthropocene: a geospatial framework from the St. Lawrence fluvial system

Over the past decades, riparian land-use changes coupled to the multiplication of river infrastructures have enhanced vulnerability issues for societies and ecosystems located along large rivers. Exposure to geohazards is also changing due to the ongoing climate change, underlining the need for flexible management strategies for riparian environments. In this perspective, GIS-based mapping allows integrating a wide range of environmental data. However, such datasets are often incomplete and not homogeneous over large geographical scales, which can be problematic for the implementation of regional land-use planning strategies. Using the St. Lawrence fluvial system (SLFS) (Québec, Canada) as a case study, this article reports and describes a high-resolution approach to map position, characteristics and erosion susceptibility of natural and artificial riverbanks from a combination of field-based, remote sensing and local knowledge-derived data. This approach allowed identifying erosion-prone sites and highlighting dominant erosion processes and spatially constrain them along the SLFS. The proposed geospatial framework constitutes (1) an initial portrait of the riverscape that will allow an effective implementation of future monitoring and process-based studies; and (2) a first step in supporting land-use planning stakeholders in the selection of appropriate measures to ensure a greater resilience of riparian communities and ecosystems.

The beaver’s menu: species and spatial selection of a European beaver population and implications for riverbank bioengineering

Riparian ecosystems are of utmost importance for many key ecosystem services, such as nutrient filtering or flood and erosion control. Restoring degraded riverbanks using soil bioengineering techniques initiates secondary succession improving both protection from erosion and riparian ecological functions. These techniques often rely on the settlement of Salicaceae and sometimes Tamaricaceae species that can be strongly impacted by beaver browsing. During the last decade European beaver (Castor fiber) populations have largely grown in France and can thus impact restored riverbanks, leading practitioners to adapt their management strategy. We conducted a study to assess the feeding preference of C. fiber and their browsing spatial pattern in semi natural riverbanks in the French Alps (Isere, France) by measuring browsing impacts along a transect. Our results indicate selective browsing occurrences at two nested spatial scales: firstly, beavers create large preferentially browsed patches (~ 8 m diameter) secondly, at a finer scale within these patches, they demonstrate a selective browsing between plant species. Among the species used in soil bioengineering, Myricaria germanica showed the lower browsing selectivity with only 2.5% of browsing probability while Salix eleagnos and Salix purpurea (10%) and Populus nigra, Salix daphnoides and Salix alba (20%) showed significant higher selectivity by beaver. Our results suggest that within the beaver presence area soil bioengineering techniques should consider adjusting both the composition and the spatial pattern of plant species settlement to mitigate the impacts of beaver on restored riverbanks.

Geochemical transformations beneath man-made ponds: Implications for arsenic mobilization in South Asian aquifers

The role of man-made ponds on arsenic mobilization was examined in Bangladesh. Here, we describe a field experiment that shows how recharge from a newly constructed pond creates a reactive front that moves downward into the underlying aquifer, but only advances slowly, less than 8 cm/year. We found that pond recharge introduces organic carbon that likely drives the reduction of sulfate and solid-phase iron. However, over the six-year period of the study the pond did not drive arsenic contamination of the underlying groundwater. An electron balance indicates that significant precipitation of ferrous iron and sulfide minerals may immobilize arsenic despite the shift towards more reducing conditions, explaining the very low observed aqueous arsenic concentrations. We additionally found that the amount of solid-phase electron acceptors available in the shallow sediments strongly retards the advance of a reduced sediment front. Our results suggest that labile organic carbon introduced by man-made ponds is efficiently mineralized in the sediments immediately below the pond bottom and thus is unlikely to drive arsenic mobilization deeper within the aquifer. We suggest that the excavation of man-made ponds removes young surficial sediments, leaving aged and less reactive sediments beneath the pond, so that recharge through excavated ponds does not mobilize arsenic at the high rates observed in recharge through natural wetlands and river banks.

Carbonate mineral identification and quantification in sediment matrices using diffuse reflectance infrared Fourier transform spectroscopy

Carbonate minerals are a major reservoir in the global carbon cycle and a key player in the sequestration and emission of atmospheric CO2. In addition to the minerals’ frequent use in agriculture and construction, carbonate formation has been targeted for anthropogenic CO2 sequestration. Due to carbonate’s importance in geological and anthropogenic realms, research on carbonate characterization and quantification is of interest. Here, we demonstrate a method to identify and quantify calcite (CaCO3) and dolomite (CaMg(CO3)2) in sediment matrices using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Needing only a few minutes per sample, DRIFTS is a rapid technique that does not require hazardous chemicals and does not destroy samples during analysis. We selected the 2515 ± 9 cm−1 absorbance bands for quantification as they exhibited little interference from sediment matrix minerals and large peak areas relative to other bands. The DRIFTS technique was compared to the traditional acidification headspace analysis method on artificial mixtures of sediment and carbonate as well as natural lake bed and river bank samples from the Upper Sangamon River Basin in Illinois, USA. DRIFTS offers an additional advantage over acidification in that it permits carbonate mineral identification simultaneously with its quantification. Though DRIFTS estimates were higher, a good correlation was found between DRIFTS and acidification estimates for both lake sediments (R2 = 0.99) and bank samples (R2 = 0.92), indicating DRIFTS is a reliable method for carbonate quantification in sediment matrices.

River Channel Forms in Relation to Bank Steepness: A Theoretical Investigation Using a Variational Analytical Method

Riverbanks vary considerably in anti-scourability and consequently take various profiles. By using an isosceles trapezoid as the generalized form of river channel cross-sections and then incorporating the effects of bank angle into the variational analytical approach developed by Huang and Nanson (2000), this study presents a detailed theoretical investigation of the self-adjustment of alluvial channel forms. It is demonstrated that when alluvial channel flow achieves stable equilibrium, a significant decrease in riverbank steepness leads to a slight decrease in maximum sediment (bedload) discharge, and yet results in a significant increase in optimal channel width and a considerable decrease in optimal channel depth. The hydraulic geometry relations, theoretically derived for bank steepness to vary across a wide range, show that among the multivariant controls, the roles of bed sediment size, channel roughness, flow discharge and sediment (bedload) discharge are independent of bank steepness. While the effects of bank steepness illustrated in the theoretically derived hydraulic geometry relations are highly consistent with the results of threshold theory and previous empirical studies, limitations on using bank angle to reflect the anti-scourability of natural riverbanks are also highlighted.

Quantitative evaluation of soil anti-erodibility in riverbank slope remediated with nature-based soil bioengineering in Liaohe River, Northeast China

Soil bioengineering techniques are considered as the cost-effective, nature-friendly, self-repairing and sustainable technique to deal with erosion problems on slopes and enhance riverbank stability, especially for shallow-seated landslides. Research on soil anti-erodibility and stability is one of the keys to understand mechanism of riverbank soil erosion. Three different types of nature-based bioengineering measures were conducted in Liaohe River Protected area and soil erodibility was evaluated in comparison with natural riverbank after four years. On the basis of soil intrinsic properties, 14 index parameters were selected to evaluate soil anti-erodibility, at the same time, soil shear strength and root dry weight were also used to assess soil stability. Results showed that nature-based bioengineering measures apparently increased riverbank stability by improving soil anti-erodibility and shear strength. Additionally, soil shear strength analysis was in agreement with soil anti-erodibility results, indicating riverbank slope soil stability in descending order were FT (Fiber roll + live stakes slope protection technique) > NT (Nonwoven fabric + live stakes slope protection technique) > CT (Condensed live stakes slope protection technique) > CK (natural riverbank). Furthermore, soil silt and silty clay, aggregate status, organic matter, root system and soil cohesion are the main factors controlling soil erodibility.

Causes and mechanisms of the destruction of the red river banks in Hanoi

The coastal territories of the Red River, passing through the city of Hanoi (the capital of Vietnam), are developed very dynamically by different types of construction, sand extraction from the river bed and its banks, pumping of water, creation of ponds and agriculture. But these activities are only possible in areas protected against annual floods with a dam. However, in recent years, the intensity of lateral erosion of the river and associated suffocation and landslide processes has become rapidly increasing in both flood and dry seasons. Deformations capture natural river banks and the dam body. The authors analysed the causes and identified mechanisms of these processes taking into account variable climatic, tectonic, hydrological, geological and hydrogeological conditions complicated by economic activities in the coastal zone. The article provides calculations of the stability of banks in different conditions (during and after the flood), which confirms theoretical ideas about the mechanism of the process and coincide with the observations. The greatest contribution to the banks destruction is the variability of the internal friction angle of the sands entering the section of the coastal territory.

Sacramento River Predator Diet Analysis: A Comparative Study

Author(s): Stompe, Dylan K.; Roberts, Jason D.; Estrada, Carlos A.; Keller, David M.; Balfour, Nicholas M.; Banet, Amanda I. | Abstract: This study examined diets of two predatory fish species, the native Sacramento Pikeminnow (Ptychocheilus grandis) and the introduced Striped Bass (Morone saxatilis), in the Sacramento River, California, USA. Both species have been implicated in native species declines through predation, eliciting our investigation of their diets in the Sacramento River. Sampling occurred between March and November 2017, and was conducted via hook and line on a 35-km reach near Chico, California. Habitat types sampled include engineered structures (water diversions and beam bridges), rip-rapped channel edges, and natural riverbank. Stomach contents were collected via gastric lavage and later processed using visual, gravimetric, and genetic techniques. Diets of Sacramento Pikeminnow and Striped Bass were highly similar as determined through index of relative importance and PERMANOVA modeling. Water temperature was the only variable that significantly affected diet composition. Results reflect similar dietary niches for both species in the Sacramento River.

Population abundance and habitat preference of the Yangtze finless porpoise in the highest density section of the Yangtze River

Abstract Habitat loss and degradation together represent one of the five major factors contributing to the rapid decline of the Yangtze finless porpoise in the Yangtze River. Protecting key habitat patches and maintaining migration corridors between habitat patches are major conservation objectives to ensure the in situ viability of the Yangtze finless porpoise. Baseline information essential for addressing these two objectives includes that pertaining to distribution and habitat preference. To investigate the distribution and habitat preferences of the Yangtze finless porpoise, five transect surveys were conducted in the Anqing section of the Yangtze River, which has the highest porpoise density among all sections of the river. Porpoise abundance estimates were calculated, and preferences for different habitat types were evaluated. The calculated porpoise abundance in the Anqing section was 181 (95% CI 125–239) animals on average. The inter‐annual and inter‐seasonal differences in porpoise abundance estimates were not significant. The natural river banks and sandbar shores were the most preferred habitats, representing 46.3 and 29.8% of the porpoise observations, respectively. In contrast, 8.1% of the porpoises were observed in habitats along reinforced river banks, which account for 38.7% of the total coastline. In subsections with natural habitat patches, porpoises were observed in almost every survey, while porpoise occurrence became highly stochastic in subsections with long reinforced river banks. These results indicate a significant tendency of the Yangtze finless porpoise to prefer natural habitats with natural river bank or sandbars but to keep away from reinforced river‐bank habitats. According to porpoise density in different subsections, free migration may be impeded or only one migration corridor remains in some subsections. Although protecting finless porpoise habitats has become a primary conservation objective, this study highlights the need to protect frequently used habitat patches and migration corridors, particularly those near natural river banks and sandbars, and to restore ecological environments along reinforced river banks.

Effect of perceived novelty on aesthetic preference

Despite the fact that perceived novelty plays an important role in aesthetic preference and is an essential force driving people to visit a place, the literature has paid a little attention to this topic. The relationship between perceived novelty and aesthetic preference is poorly known. To address this gap, this paper explores the effects of perceived novelty on aesthetic preference after 105 participants who evaluated 16 photographs of nature-based landscapes. These photographs were taken in China and North America. The results indicate that: (a) there is a strong positive relationship between perceived novelty and aesthetic preference, also, perceived novelty has a close association with complexity or mystery; (b) two landscape characteristics, sky colour and a natural river bank, contribute to an increase of the perceived novelty of a landscape; and (c) a natural river bank and fewer elements in a landscape enhance preference.

Ground Vegetation Diversity on Different Type of Riverbank Along Ciliwung River in Bogor City, West Java

Ciliwung riverbank has been affected by settlement occupation. Both concrete and another retaining wall system have been built to avoid flood and erosion to the settlement that has existed adjacent to the river. Built environment as human disturbance can trigger the change of species richness of ground vegetation in the Ciliwung riverbank of Bogor City. The research objective is to study the difference of ground vegetation biodiversity in three different types of riverbank based on its condition: natural, semi-natural, and constructed riverbanks. Point method and photographic sampling are used. Five replications of a square metre plot at three transects were placed at four sites sampling along 250 m each from the three different types of riverbank. Images of the plots are trained using sample point to overcome the difficulties in the field observation and statistical analysis. The result discovered that species richness in the natural riverbank is significantly higher than in semi-natural and constructed riverbank. Yet, no significance of species richness is shown between semi-natural and constructed riverbank. Total species of ground vegetation that we found were 55 species. Each different type of riverbank has its own highest species coverage: Asystasia nemorum (55.00%) in the natural riverbank, Pilea nummulariifolia (33.07%) in the semi-natural riverbank, and Pogonatherum crinitum (52.80%) in the constructed riverbank. The study concluded that the construction in the riverbank largely altered the biodiversity of ground vegetation in the urban riverbank. The outcomes suggest that the remnant of natural riverbank in the urban landscape should be highly protected from urban development to preserve its biodiversity. Also, species found could be potentially developed as landscape plants to support urban river planning, design, and management.