Index of medium-class flood disturbance for increasing diversity of vegetation area at gravel bars or islands in middle of rivers

2012 ◽  
Vol 10 (3) ◽  
pp. 255-267 ◽  
Author(s):  
Norio Tanaka ◽  
Junji Yagisawa
Keyword(s):  
Flood Disturbance ◽  
Gravel Bars

scholarly journals Heterogeneity of soil carbon pools and fluxes in a channelized and a restored floodplain section (Thur River, Switzerland)

2011 ◽  
Vol 8 (1) ◽  
pp. 1059-1091 ◽  
Author(s):  
E. Samaritani ◽  
J. Shrestha ◽  
B. Fournier ◽  
E. Frossard ◽  
F. Gillet ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Spatial Heterogeneity ◽  
Soil Properties ◽  
Ecosystem Functions ◽  
Flood Disturbance ◽  
Organic C ◽  
C Pools ◽  
C Dynamics ◽  
Wide Range ◽  
Gravel Bars

Abstract. Due to their spatial complexity and dynamic nature, floodplains provide a wide range of ecosystem functions. However, because of flow regulation, many riverine floodplains have lost their characteristic heterogeneity. Restoration of floodplain habitats and the rehabilitation of key ecosystem functions has therefore become a major goal of environmental policy. Many important ecosystem functions are linked to organic carbon (C) dynamics in riparian soils. The fundamental understanding of the factors that drive the processes involved in C cycling in heterogeneous and dynamic systems such as floodplains is however only fragmentary. We quantified soil organic C pools (microbial C and water extractable organic C) and fluxes (soil respiration and net methane production) in functional process zones of adjacent channelized and widened sections of the Thur River, NE Switzerland, on a seasonal basis. The objective was to assess how spatial heterogeneity and temporal variability of these pools and fluxes relate to physicochemical soil properties on one hand, and to soil environmental conditions and flood disturbance on the other hand. Overall, factors related to seasonality and flooding (temperature, water content, organic matter input) affected soil C dynamics more than soil properties did. Coarse-textured soils on gravel bars in the restored section were characterized by low base-levels of organic C pools due to low TOC contents. However, frequent disturbance by flood pulses led to high heterogeneity with temporarily and locally increased pools and soil respiration. By contrast, in stable riparian forests, the finer texture of the soils and corresponding higher TOC contents and water retention capacity led to high base-levels of C pools. Spatial heterogeneity was low, but major floods and seasonal differences in temperature had additional impacts on both pools and fluxes. Soil properties and base levels of C pools in the dam foreland of the channelized section were similar to the gravel bars of the restored section. By contrast, spatial heterogeneity, seasonal effects and flood disturbance were similar to the forests, except for indications of high CH4 production that are explained by long travel times of infiltrating water favouring reducing conditions. Overall, the restored section exhibited both a larger range and a higher heterogeneity of organic C pools and fluxes as well as a higher plant biodiversity than the channelized section. This suggests that restoration has indeed led to an increase in functional diversity.

scholarly journals Heterogeneity of soil carbon pools and fluxes in a channelized and a restored floodplain section (Thur River, Switzerland)

2011 ◽  
Vol 15 (6) ◽  
pp. 1757-1769 ◽  
Author(s):  
E. Samaritani ◽  
J. Shrestha ◽  
B. Fournier ◽  
E. Frossard ◽  
F. Gillet ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Spatial Heterogeneity ◽  
Soil Properties ◽  
Ecosystem Functions ◽  
Flood Disturbance ◽  
Organic C ◽  
C Pools ◽  
C Dynamics ◽  
Wide Range ◽  
Gravel Bars

Abstract. Due to their spatial complexity and dynamic nature, floodplains provide a wide range of ecosystem functions. However, because of flow regulation, many riverine floodplains have lost their characteristic heterogeneity. Restoration of floodplain habitats and the rehabilitation of key ecosystem functions, many of them linked to organic carbon (C) dynamics in riparian soils, has therefore become a major goal of environmental policy. The fundamental understanding of the factors that drive the processes involved in C cycling in heterogeneous and dynamic systems such as floodplains is however only fragmentary. We quantified soil organic C pools (microbial C and water extractable organic C) and fluxes (soil respiration and net methane production) in functional process zones of adjacent channelized and widened sections of the Thur River, NE Switzerland, on a seasonal basis. The objective was to assess how spatial heterogeneity and temporal variability of these pools and fluxes relate to physicochemical soil properties on one hand, and to soil environmental conditions and flood disturbance on the other hand. Overall, factors related to seasonality and flooding (temperature, water content, organic matter input) affected soil C dynamics more than soil properties did. Coarse-textured soils on gravel bars in the restored section were characterized by low base-levels of organic C pools due to low TOC contents. However, frequent disturbance by flood pulses led to high heterogeneity with temporarily and locally increased C pools and soil respiration. By contrast, in stable riparian forests, the finer texture of the soils and corresponding higher TOC contents and water retention capacity led to high base-levels of C pools. Spatial heterogeneity was low, but major floods and seasonal differences in temperature had additional impacts on both pools and fluxes. Soil properties and base levels of C pools in the dam foreland of the channelized section were similar to the gravel bars of the restored section. By contrast, spatial heterogeneity, seasonal effects and flood disturbance were similar to the forests, except for indications of high CH4 production that are explained by long travel times of infiltrating water favoring reducing conditions. Overall, the restored section exhibited both a larger range and a higher heterogeneity of organic C pools and fluxes as well as a higher plant biodiversity than the channelized section. This suggests that restoration has indeed led to an increase in functional diversity.

Catastrophic flood disturbance and a community's response to plant resilience in the heart of the Texas Hill Country

Geomorphology ◽  
2018 ◽  
Vol 305 ◽  
pp. 20-32 ◽  
Author(s):  
Kimberly M. Meitzen ◽  
John N. Phillips ◽  
Thaïs Perkins ◽  
Aspen Manning ◽  
Jason P. Julian
Keyword(s):  
Flood Disturbance ◽  
Hill Country ◽  
Catastrophic Flood

Sprouting and genetic structure vary with flood disturbance in the tropical riverine paperbark tree,Melaleuca leucadendra(Myrtaceae)

2013 ◽  
Vol 100 (11) ◽  
pp. 2250-2260 ◽  
Author(s):  
Caroline Chong ◽  
Will Edwards ◽  
Richard Pearson ◽  
Michelle Waycott
Keyword(s):  
Genetic Structure ◽  
Flood Disturbance ◽  
Melaleuca Leucadendra

scholarly journals Population dynamics of five riverbed breeding bird species on the lower Drava River, NE Slovenia

Acrocephalus ◽  
2017 ◽  
Vol 38 (174-175) ◽  
pp. 85-126
Author(s):  
Luka Božič ◽  
Damijan Denac
Keyword(s):  
Population Dynamics ◽  
Bird Species ◽  
Breeding Population ◽  
Population Increase ◽  
General Situation ◽  
Breeding Bird ◽  
Main River Channel ◽  
Extreme Flood ◽  
Gravel Bars ◽  
Gravel Bar

AbstractIn 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed PloverCharadrius dubiusoccurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m3/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common SandpiperActitis hypoleucosremained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. KingfisherAlcedo atthiswas fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand MartinRiparia ripariasince 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White WagtailMotacilla alba, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.

18.—Sedimentation in some Scottish Rivers of Low Sinuosity

1976 ◽  
Vol 69 (18) ◽  
pp. 425-456 ◽  
Author(s):  
B. J. Bluck
Keyword(s):  
Water Level ◽  
High Flow ◽  
Sediment Type ◽  
Meandering Streams ◽  
Bed Forms ◽  
Gravel Bars ◽  
The Mean ◽  
Flow Stage ◽  
Stream Direction ◽  
Maximum Rise

SynopsisScottish streams of low sinuosity have four kinds of bars, three are bank-attached (lateral), and one is medial. Bar type is related to sinuosity, and as streams often increase in sinuosity away from source, there tends to be a variation in bar type successively downstream. The morphology and structure of the bars are related to grain size—gravel bars do not have the same bed forms and structures as those made of sand—and variations in flow stage. The bar head, composed mostly of gravel, forms during the high-flow stage, and as the flow falls so sediments of the lee face record the changing flow pattern. With further drop in water level the locus of sedimentation shifts to the bar tail where the dwindling flow may build diversely oriented bed forms and structures. Changes in the rate of fall, or differences in the maximum rise of water level, result in different proportions of sediment type being deposited.The mean orientation of the directional structures is not always alined with the mean stream direction, and the diversity of orientation is comparable with the diversity in orientation of directional structures in meandering streams. The variability in orientation is due to the effects of flood-produced bed forms in diverting the low-stage flow, stream sinuosity, and the changing orientation of the channel as it sweeps across the floodplain.

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