Mountain streams act as conveyors of sediments within the river continuum,where the physical transport of sediments between river reaches through the catchment or between individual parts(e.g.,between hillslopes and c...Mountain streams act as conveyors of sediments within the river continuum,where the physical transport of sediments between river reaches through the catchment or between individual parts(e.g.,between hillslopes and channels)of the catchment is assumed.This study focused on sediment connectivity analysis in the SlavíčRiver catchment in the MoravskoslezskéBeskydy Mts in the eastern part of the Czech Republic.The connectivity index and connectivity index target modelling were combined with an analysis of anthropogenic interventions.Additionally,field mapping,grain size of bed sediments and stream power analysis were used to obtain information about connectivity in the catchment.Based on the analysis and obtained results,terrain topography is the current main driving factor affecting the connectivity of sediment movement in the SlavíčRiver catchment.However,the modelling provided valuable information about high sediment connectivity despite different recent land use conditions(highly forested area of the catchment)than those in historical times from the 16th to 19th centuries when the SlavíčRiver catchment was highly deforested and sediment connectivity was probably higher.The analysis of anthropogenic interventions,field mapping,grain size of bed sediments and stream power analysis revealed more deceleration of sediment movement through the catchment,decreased sediment connectivity with bed erosion,and gradual river channel process transformation in some reaches.Field mapping has identified various natural formations and human-induced changes impacting the longitudinal and lateral connectivity in the SlavíčRiver.For instance,embankments along 48%of the river's length,both on the right and left banks,significantly hinder lateral sediment supply to the channel.Stream power index analysis indicates increased energy levels in the flowing water in the river's upper reaches(up to 404.8 W m^(-2)).This high energy is also observed in certain downstream sections(up to 337.6 W m^(-2)),where it is influenced by human activities.These conditions lead to intensified erosion processes,playing a crucial role in sediment connectivity.Similar observations were described in recent studies that pointed out the long-term human interventions on many streams draining European mountains,where a decrease in sediment connectivity in these streams is linked with sediment deficits and the transformation of processes forming channels.展开更多
Ephemeral and perennial streams of mountainous catchments in Sabaragamuwa Province of Sri Lanka and Hong Kong of China were studied for two years on vegetation dynamics.Each year,sampling was conducted during a period...Ephemeral and perennial streams of mountainous catchments in Sabaragamuwa Province of Sri Lanka and Hong Kong of China were studied for two years on vegetation dynamics.Each year,sampling was conducted during a period when ephemeral streams had low surface flows.Sampling was realized contiguously using belt transects.The standing crop biomass(hereafter biomass)of herbaceous vegetation in ephemeral channels was comparatively lower than perennials and so was the herb diversity.Herb diversity showed a peak from 1.5 to 4.5 m from the centerline/thalweg of ephemeral and perennial streams.Out of 24 herbs,only three were common for both.A peak herb biomass zone was observed in perennials in the same region where diversity peaked.In ephemerals,herb biomass increased laterally up to^1.5 m,and was constant thereafter.Seedling experiment results tallied with the field diversity observations of both stream types,and suggested that seed dispersion was the main reason for herb colonization.Furthermore,it showed sapling emergence to be significantly higher in perennials than ephemerals.Return period of annual maximum monthly rainfall was a strong indicator of age of trees in ephemeral streams,and elucidated the possibility of hindcasting past flow episodes.Electrical conductivity was significantly high in ephemeral streams among all the water quality parameters.The contents of the water nutrients were approximately the same in both stream types.While recommending further studies on eco-hydrology of ephemerals,we recognize ephemeral streams to be valuable references in climate change studies due to their responsiveness and representativeness in long term hydrological changes.展开更多
Small water bodies are critical for maintaining freshwater biodiversity,but are among the least investigated aquatic environments.We examined physical and chemical variables at two reaches in Arroyo Tambillos,a small,...Small water bodies are critical for maintaining freshwater biodiversity,but are among the least investigated aquatic environments.We examined physical and chemical variables at two reaches in Arroyo Tambillos,a small,high-elevation Andean stream,in NW Mendoza province,Argentina,across four seasons to examine how local factors and seasonality affected the structure of the macroinvertebrate community.The Arroyo Tambillos community was numerically dominated by ephemeropterans(mainly Massartellopsis irarrazavali)while the dipteran Chironomidae were the most species rich.Total macroinvertebrate abundance was highest in summer,driven mainly by taxa that were secondary in dominance(Austrelmis sp.and Andesiops peruvianus),while richness did not differ between seasons.However,benthic composition was different in Fall 2013(March)compared to other seasons,largely because of the increased abundance of Chironomidae.Canonical correspondence analysis discriminated Chironomidae species distributions in Fall 2013 by substrate type(i.e.,big and small boulder substrate).By contrast,discharge,velocity,and depth were the variables which most affected the macroinvertebrate abundance and distributions.Contrary to our expectations,most community changes observed occurred in fall instead of summer.Nivo-kryal stream communities like the one described here have become increasingly important for conserving mountain stream biodiversity as anthropogentic impacts and climate change increasingly impact lower stream reaches.Therefore,monitoring high-altitude streams like the Arroyo Tambillos may be critical for preventing the future loss of unique and sensitive stream biota.展开更多
The goal of this review paper is to provide a list of methods and devices used to measure sediment accumulation in wadeable streams dominated by cobble and gravel substrate. Quantitative measures of stream sedimentati...The goal of this review paper is to provide a list of methods and devices used to measure sediment accumulation in wadeable streams dominated by cobble and gravel substrate. Quantitative measures of stream sedimentation are useful to monitor and study anthropogenic impacts on stream biota, and stream sedimentation is measurable with multiple sampling methods. Evaluation of sedimentation can be made by measuring the concentration of suspended sediment, or turbidity, and by determining the amount of deposited sediment, or sedimentation on the streambed. Measurements of deposited sediments are more time consuming and labor intensive than measurements of suspended sediments. Traditional techniques for characterizing sediment composition in streams include core sampling, the shovel method, visual estimation along transects, and sediment traps. This paper provides a comprehensive review of methodology, devices that can be used, and techniques for processing and analyzing samples collected to aid researchers in choosing study design and equipment.展开更多
Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in ...Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in structure and species composition, are dominant along these river banks: Aquatic vegetation, Wetbanks, Palmiet, Scrub, Forest and Shrubland(Fynbos). The study aims to correlate the vegetation patterns to flooding patterns, in particular the inundation frequency and stream power. A problem arises: because these catchments are ungauged, like most mountain catchments, with the only weirs at the downstream end of the catchment. Discharge data at the weirs are extrapolated to the sites upstream by multiplication with a factor based on the size of the subcatchment that drains through a sample site. In this way, recurrence intervals for floods in mountain streams are derived. Discharges at sites are also calculated using bed roughness(Manning's n) and slope in straight sections with uniform flow conditions. Stream power is derived from the discharges calculated in this manner. The combination of stream power and recurrence intervals explains the occurrence of most vegetation types occurring on the banks, except for one type: Afromontane Forest. This type is probably more dependent on other factors, such as protection from fire and the depth of the groundwater table.展开更多
Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined us...Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined using the exposed roots of the trees.For this purpose,8 reaches of Lavij Stream were investigated.To determine the first year of root exposure,two sets of macroscopic and microscopic indicators were utilized.Accordingly,the rate of the stream bank erosion was estimated.The results were analyzed by using statistical test,which showed insignificant differences between the two groups of indicators.Due to its more abundance(frequency)on the margins and easy detection of its root through the exposure(macroscopic and microscopic)indicators,Alnus glutinosa(black alder)species could be more easily and accurately analyzed as compared with any other tree species in the region.The mean erosion rate of the riverbank using the extruded roots was estimated to be 0.08 m/yr.The hydrological analyses of flood flows showed that 95%of Lavij Stream bank erosion was caused by the river bank full discharges with a return period of 1-3 years.展开更多
基金supported by an internal grant of the University of Ostrava[SGS10/PřF/2021-Specificity of fluvial landscape in the context of historical and future changes].
文摘Mountain streams act as conveyors of sediments within the river continuum,where the physical transport of sediments between river reaches through the catchment or between individual parts(e.g.,between hillslopes and channels)of the catchment is assumed.This study focused on sediment connectivity analysis in the SlavíčRiver catchment in the MoravskoslezskéBeskydy Mts in the eastern part of the Czech Republic.The connectivity index and connectivity index target modelling were combined with an analysis of anthropogenic interventions.Additionally,field mapping,grain size of bed sediments and stream power analysis were used to obtain information about connectivity in the catchment.Based on the analysis and obtained results,terrain topography is the current main driving factor affecting the connectivity of sediment movement in the SlavíčRiver catchment.However,the modelling provided valuable information about high sediment connectivity despite different recent land use conditions(highly forested area of the catchment)than those in historical times from the 16th to 19th centuries when the SlavíčRiver catchment was highly deforested and sediment connectivity was probably higher.The analysis of anthropogenic interventions,field mapping,grain size of bed sediments and stream power analysis revealed more deceleration of sediment movement through the catchment,decreased sediment connectivity with bed erosion,and gradual river channel process transformation in some reaches.Field mapping has identified various natural formations and human-induced changes impacting the longitudinal and lateral connectivity in the SlavíčRiver.For instance,embankments along 48%of the river's length,both on the right and left banks,significantly hinder lateral sediment supply to the channel.Stream power index analysis indicates increased energy levels in the flowing water in the river's upper reaches(up to 404.8 W m^(-2)).This high energy is also observed in certain downstream sections(up to 337.6 W m^(-2)),where it is influenced by human activities.These conditions lead to intensified erosion processes,playing a crucial role in sediment connectivity.Similar observations were described in recent studies that pointed out the long-term human interventions on many streams draining European mountains,where a decrease in sediment connectivity in these streams is linked with sediment deficits and the transformation of processes forming channels.
基金funded by the Research Grants Council Fund of Hong Kong(Project number:Poly U152161/14E)Environment and Conservation Fund,Hong Kong(Project number:39/2011)。
文摘Ephemeral and perennial streams of mountainous catchments in Sabaragamuwa Province of Sri Lanka and Hong Kong of China were studied for two years on vegetation dynamics.Each year,sampling was conducted during a period when ephemeral streams had low surface flows.Sampling was realized contiguously using belt transects.The standing crop biomass(hereafter biomass)of herbaceous vegetation in ephemeral channels was comparatively lower than perennials and so was the herb diversity.Herb diversity showed a peak from 1.5 to 4.5 m from the centerline/thalweg of ephemeral and perennial streams.Out of 24 herbs,only three were common for both.A peak herb biomass zone was observed in perennials in the same region where diversity peaked.In ephemerals,herb biomass increased laterally up to^1.5 m,and was constant thereafter.Seedling experiment results tallied with the field diversity observations of both stream types,and suggested that seed dispersion was the main reason for herb colonization.Furthermore,it showed sapling emergence to be significantly higher in perennials than ephemerals.Return period of annual maximum monthly rainfall was a strong indicator of age of trees in ephemeral streams,and elucidated the possibility of hindcasting past flow episodes.Electrical conductivity was significantly high in ephemeral streams among all the water quality parameters.The contents of the water nutrients were approximately the same in both stream types.While recommending further studies on eco-hydrology of ephemerals,we recognize ephemeral streams to be valuable references in climate change studies due to their responsiveness and representativeness in long term hydrological changes.
基金Funding was provided by the National Science Foundation(NSF DEB-06-42512 to T.W.)UW-Eau Claire’s Center for International Educationsupported by Consejo Nacional de Investigaciones Científicas y Técnicas(CONICET),Argentina。
文摘Small water bodies are critical for maintaining freshwater biodiversity,but are among the least investigated aquatic environments.We examined physical and chemical variables at two reaches in Arroyo Tambillos,a small,high-elevation Andean stream,in NW Mendoza province,Argentina,across four seasons to examine how local factors and seasonality affected the structure of the macroinvertebrate community.The Arroyo Tambillos community was numerically dominated by ephemeropterans(mainly Massartellopsis irarrazavali)while the dipteran Chironomidae were the most species rich.Total macroinvertebrate abundance was highest in summer,driven mainly by taxa that were secondary in dominance(Austrelmis sp.and Andesiops peruvianus),while richness did not differ between seasons.However,benthic composition was different in Fall 2013(March)compared to other seasons,largely because of the increased abundance of Chironomidae.Canonical correspondence analysis discriminated Chironomidae species distributions in Fall 2013 by substrate type(i.e.,big and small boulder substrate).By contrast,discharge,velocity,and depth were the variables which most affected the macroinvertebrate abundance and distributions.Contrary to our expectations,most community changes observed occurred in fall instead of summer.Nivo-kryal stream communities like the one described here have become increasingly important for conserving mountain stream biodiversity as anthropogentic impacts and climate change increasingly impact lower stream reaches.Therefore,monitoring high-altitude streams like the Arroyo Tambillos may be critical for preventing the future loss of unique and sensitive stream biota.
文摘The goal of this review paper is to provide a list of methods and devices used to measure sediment accumulation in wadeable streams dominated by cobble and gravel substrate. Quantitative measures of stream sedimentation are useful to monitor and study anthropogenic impacts on stream biota, and stream sedimentation is measurable with multiple sampling methods. Evaluation of sedimentation can be made by measuring the concentration of suspended sediment, or turbidity, and by determining the amount of deposited sediment, or sedimentation on the streambed. Measurements of deposited sediments are more time consuming and labor intensive than measurements of suspended sediments. Traditional techniques for characterizing sediment composition in streams include core sampling, the shovel method, visual estimation along transects, and sediment traps. This paper provides a comprehensive review of methodology, devices that can be used, and techniques for processing and analyzing samples collected to aid researchers in choosing study design and equipment.
基金supported by funding from the National Research Foundation to C. Boucher and the VSB Funds (the Netherlands) to E. Siebenadditional funding from the Water Research Commission
文摘Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in structure and species composition, are dominant along these river banks: Aquatic vegetation, Wetbanks, Palmiet, Scrub, Forest and Shrubland(Fynbos). The study aims to correlate the vegetation patterns to flooding patterns, in particular the inundation frequency and stream power. A problem arises: because these catchments are ungauged, like most mountain catchments, with the only weirs at the downstream end of the catchment. Discharge data at the weirs are extrapolated to the sites upstream by multiplication with a factor based on the size of the subcatchment that drains through a sample site. In this way, recurrence intervals for floods in mountain streams are derived. Discharges at sites are also calculated using bed roughness(Manning's n) and slope in straight sections with uniform flow conditions. Stream power is derived from the discharges calculated in this manner. The combination of stream power and recurrence intervals explains the occurrence of most vegetation types occurring on the banks, except for one type: Afromontane Forest. This type is probably more dependent on other factors, such as protection from fire and the depth of the groundwater table.
文摘Powerful alluvial rivers in the northern Alborz mountain ranges erode river banks due to having high slopes.Most of these rivers flow in forest areas.In this research,the rate of the river bank erosion was examined using the exposed roots of the trees.For this purpose,8 reaches of Lavij Stream were investigated.To determine the first year of root exposure,two sets of macroscopic and microscopic indicators were utilized.Accordingly,the rate of the stream bank erosion was estimated.The results were analyzed by using statistical test,which showed insignificant differences between the two groups of indicators.Due to its more abundance(frequency)on the margins and easy detection of its root through the exposure(macroscopic and microscopic)indicators,Alnus glutinosa(black alder)species could be more easily and accurately analyzed as compared with any other tree species in the region.The mean erosion rate of the riverbank using the extruded roots was estimated to be 0.08 m/yr.The hydrological analyses of flood flows showed that 95%of Lavij Stream bank erosion was caused by the river bank full discharges with a return period of 1-3 years.
