Distribution Of Riparian Vegetation Research Articles

Short‐term biogeomorphology of a gravel‐bed river: Integrating remote sensing with hydraulic modelling and field analysis

AbstractIn recent decades, fluvial geomorphology and ecohydraulic research have extensively used field observations, remote sensing or hydrodynamic modelling to understand river systems. This study presents an innovative approach that combines field surveys, Light Detection and Ranging (LiDAR)‐based topographical and biomass analyses and model‐derived hydro‐morphodynamic geostatistics to examine short‐term biogeomorphological changes in the wandering gravel‐bed Orco River in Italy. Our primary hypothesis is that hydro‐morphological variables can be robust descriptors for riparian vegetation distribution. From a geomorphological perspective, our study confirms the prevalent wandering behaviour of the Orco River. Moreover, we identified a widening trend in braiding and anabranching sections, particularly downstream. This is evident because of hotspots of flood‐induced morphological reactivation and the redistribution of sediments from the riverbed to lateral bars, resulting in a multi‐thread pattern. Our analysis reveals a net increase in biomass during the observation period despite frequent flood disturbances. We attributed it to two opposing biogeomorphological dynamics: the reduced flow disturbance in some regions due to flood‐induced geomorphological changes and the self‐healing of lateral connectivity through river wandering. Such a net increase indicates that transitional rivers store carbon in the form of vegetation biomass due to their short‐term morphological instability and the different timescales between vegetation and morphological adjustments. Finally, we supported our initial hypothesis with three key findings: (i) a signature of vegetation not just on topography but also on hydro‐morphological conditions, summarised by inundation probability; (ii) the lower variance in vertical topographical changes in vegetated areas compared with bare ones; and (iii) the introduction of a new parameter, named inundation viscosity, derived from the product of mean bed shear stress and average inundation duration, as a discriminating factor for colonisation conditions. These results underscore the value of our comprehensive approach.

Dam inundation duration as a dominant constraint on riparian vegetation recovery

The identification of limiting factors is essential for the ecological restoration of riparian ecosystems degraded by the damming of rivers, but remains unclear. Here, we quantitatively assessed the relative importance of environmental factors and revealed the main limiting factors for riparian vegetation restoration and their influencing mechanisms, using riparian plant and environmental data of seven large reservoirs in southwest China. We found that inundation duration had a significantly greater effect on riparian vegetation distribution, cover and diversity than environmental factors such as inundation depth, rainfall, humidity, temperature, sunshine hours, aspect, slope, surface relief, soil pH, available nitrogen (AN), available phosphorus (AP), and available potassium (AK); vegetation cover, species richness, complexity and dominance were highly significantly negatively correlated with inundation duration (p < 0.01); inundation for 5 months is close to the tolerance limit of most plants and poses a significant limiting effect on the vegetation restoration in the reservoir riparian. Therefore, the inundation duration should be highlighted in riparian vegetation restoration. Meanwhile, incorporating the riparian inundation into the river ecological scheduling objectives to shorten the inundation duration and thus radically alleviate the limitation is a new opportunity for vegetation restoration in the reservoir riparian.

Spatial Distribution of Vegetation on Stream Bars and the Riparian Zone Reflects Successional Pattern Due to Fluid Dynamics of River

The river is a dynamic space where erosion, transportation, and sedimentation are constantly occurring due to running water. This study aims to reveal the change in geomorphology caused by the flow characteristics of water in rivers and the response of vegetation to that. This study was carried out by clarifying the spatially appearing successional trends in the vegetation established in the stream bars and the riparian zones, which are located on different topographic conditions based on the vegetation profile, ordination result, and species diversity. The spatial distribution of vegetation on the stream bars tended to appear in the order of annual plant-, perennial plant-, and tree-dominated stands from the upstream toward a downstream direction (a gravel bar and a sand bar in a mountain gravel-bed river and an estuary, respectively) or the reversed one (a sand bar in a lowland river). The spatial distribution of vegetation on the riparian zones tended to appear in the order of annual plant-, perennial plant-, and tree-dominated stands from the waterfront toward the bank direction. Changes in species composition also differed depending on the spatial location, showing a similar trend to the spatial distribution of vegetation. Species diversity became higher in proportion to the longevity of the dominant species of each vegetation type. In conclusion, the longitudinal distribution pattern of vegetation on the stream bars resembles the lateral distribution of riparian vegetation, and the successional trends follow the spatial distribution pattern. These results suggest that the dynamics of bed loading, an allogenic process, may be an important determinant of the spatial distribution and succession of plant communities in dynamic riverine environments.

Role of Channel Migration and Influencing Hydro-Geomorphic Attributes in Dibru River Basin Using Remote Sensing and GIS

The action of the river is dynamic and exhibits morphological changes over time. River channel migration may take place because of sedimentation, geology, soil properties, geomorphic setup, precipitation, land use pattern, natural bank geometry (e.g., channel width, meander length, meander wavelength, amplitude, the radius of curvature, arc angle, and sinuosity), discharges of various frequencies (Brice 1982, MacDonald et al. 1991, Garcia et al. 1994), distribution of riparian vegetation, and vertical and horizontal heterogeneity of floodplain soils (Motta et al. 2012), etc. are some factors for channel migration. The present study is undertaken in the Dibru River Basin, the left-bank tributary of the Brahmaputra River. To identify the Spatio-temporal changes, satellite imagery is used in the GIS environment. The extraction of the river is done from the GIS software (Arc GIS 10.4) by digitizing process and tries to overlay the different time periods of shifting of the river and find out the rate of magnitude and nature of the river course changes. An interval of 10 years is taken to find the rate of magnitude and nature of changes in the river courses from satellite imagery. The time period is taken from 1977-2020 at 10 years intervals. Along with the rate of river course changes, channel avulsion is also shown with the help of satellite imagery. The Dibru Saikhowa National Park falls within the Dibru river basin, where numerous streams are found, within the national park. The Saikhoa river and Ajuka river flow within the national park. The Sursa river is a small channel linked with the Dangori river. With phases of time, the river made a headward erosion and confluence with the Ajuka river and formed a channel. The Saikhoa river flowed till 1987; due to deposition, the river abandoned its original course. In 1988, the Ajuka river and Sursa river merged and flowed northwest direction. The high discharges of the Lohit river diverted towards the Ajuka and Sursa Rivers and took a new channel named the Lower course of Lohit river within the study area. It can be called an avulsion channel because it changed its direction from its original to a new course in 1990. Since 1990, the course of the channel has been tremendously expanding its length and breadth, causing a flood, bank erosion, and deposition nearby human habitats and Dibru Saikhowa National Park. From the multi-temporal satellite imagery, the river courses were studied, and found the year of avulsion took place in the channel. Multi-temporal satellite imagery is used to identify the channel’s avulsion. An avulsion is the rapid separation of a river channel to form a new course, which is only possible due to flood, high discharge, soil properties or tectonic activity, etc. that creates instability and causes the channel avulsion.

Spatial Pattern and Key Environmental Determinants of Vegetation in Sand Mining and Non-Mining Sites along the Panjkora River Basin

A specific set of environmental conditions characterizes plant species patterns and distribution on Earth. Similarly, riparian vegetation can be impacted by anthropogenic activities like mining practices involving the removal of vegetation cover, which destroys the structure and diversity of the habitat, adversely affecting the ecosystem services. In this study, we explored the role of environmental variables and biotic intervention in deriving spatial patterns and distribution of riparian vegetation at mining and non-mining sites along the most depleted Panjkora River basin in NW Pakistan. Vegetation data and its determining factors at 28 mining and non-mining sites (14 each) were sampled using 10 m × 10 m (100 m2) systematic plots at 50 m intervals along transects in a downstream direction from the upper catchments to the bottom junction with the Swat River. We recorded 186 species in both mining and non-mining sites, belonging to 70 families comprising 174 angiosperms, 3 gymnosperms, and 9 Pteridophytes. Results show that annual or perennial therophytic life forms predominated in the Panjkora River system, indicating anthropogenic disturbances. At the same time, the aggressively invasive species, such as Xanthium strumarium and Cannabis sativa, further heightened plant community disturbances. Generally, the species diversity was higher in non-mining sites and may be attributed to habitat fragmentation. Likewise, the Canonical Correspondence Analysis (CCA-ordination) revealed that geographic coordinate (i.e., latitude r = 0.80; longitude r = 0.75) and elevation (r = 0.95) were more meaningful predictors than soil texture (i.e., silt%, r = −0.30), nutrients (i.e., potassium, r = −0.35; phosphorus, r = 0.38) and soil pH (r = −0.50) in shaping the spatial pattern and vegetation structure. Our result implies that the present vegetation composition and spatial assemblages are due to heavy anthropogenic interventions, especially mining activities. Therefore, the heavily degraded fragile riparian system of the Panjkora River and its tributaries needed to be conserved and restored by predicting the composition of communities in response to changing climatic conditions.

Open Source Riverscapes: Analyzing the Corridor of the Naryn River in Kyrgyzstan Based on Open Access Data

In fluvial geomorphology as well as in freshwater ecology, rivers are commonly seen as nested hierarchical systems functioning over a range of spatial and temporal scales. Thus, for a comprehensive assessment, information on various scales is required. Over the past decade, remote sensing-based approaches have become increasingly popular in river science to increase the spatial scale of analysis. However, data-scarce areas have been widely ignored so far, even if most remaining free flowing rivers are located in such areas. In this study, we suggest an approach for river corridor mapping based on open access data only, in order to foster large-scale analysis of river systems in data-scarce areas. We take the more than 600 km long Naryn River in Kyrgyzstan as an example, and demonstrate the potential of the SRTM-1 elevation model and Landsat OLI imagery in the automated mapping of various riverscape parameters, like the riparian zone extent, distribution of riparian vegetation, active channel width and confinement, as well as stream power. For each parameter, a rigor validation is performed to evaluate the performance of the applied datasets. The results demonstrate that our approach to riverscape mapping is capable of providing sufficiently accurate results for reach-averaged parameters, and is thus well-suited to large-scale river corridor assessment in data-scarce regions. Rather than an ultimate solution, we see this remote sensing approach as part of a multi-scale analysis framework with more detailed investigation in selected study reaches.

Lateral and longitudinal distribution of riparian vegetation along an ephemeral river in Namibia using remote sensing techniques

Ephemeral rivers are key features of desert ecosystems, providing shallow groundwater and occasional surface flow, but compared to perennial systems, the structure of riparian forests in ephemeral rivers and their interactions with the hydrologic regime are poorly understood. This study examines the distribution of riparian woody species in the ephemeral Kuiseb River in central Namibia. Unmanned aerial vehicle (UAV) and satellite imagery were used to examine the structure of the riparian forest across lateral and longitudinal gradients. Woody plant abundance peaked in the terminal alluvial zone, the reach of the river where floods typically run dry. The five dominant species exhibited similar spatial patterns at latitudinal and longitudinal scales. Faidherbia albida and Salvadora persica were found more proximal to the active channel and concentrated in the terminal alluvial zone. Acacia (Vachellia) erioloba, Euclea pseudebenus, and Tamarix usneoides were more evenly dispersed laterally across the riparian zone and along the river's longitudinal profile. These spatial patterns correspond to plant physiological properties of hydrological dependence and gradients of water availability and soil composition. The tight coupling of plant distributions with water availability highlights the need for long-term monitoring of ephemeral riparian vegetation in light of potential future changes to the global hydrologic regime.

Impact of Slightly-Curved Riparian Vegetation Distribution on Hyporheic Lateral Exchange solute migration

Riparian hyporheic exchange has a very important role in blocking and reducing pollution. In order to quantitatively grasp the self-purification ability of the river and predict the change of water quality, it is necessary to have a good understanding of the process that drives river water into the hyporheic layer. In this paper, the effects of slightly-curved riparian and vegetation density on the hyporheic lateral exchange of solute migration were studied in depth through model tests. The results show that: (1) The vegetation spacing d has a significant effect on the hyporheic lateral exchange. As the lateral spacing of vegetation decreases, the rate of hyporheic lateral exchange increases. (2) The amplitude a has a significant effect on the hyporheic lateral exchange. As the amplitude a increases, the faster the hyporheic lateral exchange rate on convex surface, and the larger the feather forward area of solute migration. However, due to the expansion of the volume of the retention area on the concave surface, it has a suppressive effect on the disturbance pressure and delays the solute transport. (3) There is a certain asymptotic limit for the increase of the hyporheic lateral exchange width, when the ratio of the underground pore water concentration C′ to the surface circulating water concentration C0′in the riparian zone is equal to 0.50, the solute transport width can be approximated as a suitable width for the hyporheic lateral exchange. The results are expected to provide a certain reference for the theoretical research of riparian hyporheic exchange.

Floristics, Leaf Size Spectra and Life-form Distribution of Riparian Vegetation along a Hill Stream, Bhaderwah, Jammu and Kashmir, India

Floristics, Leaf Size Spectra and Life-form Distribution of Riparian Vegetation along a Hill Stream, Bhaderwah, Jammu and Kashmir, India

Meandering and Land Use /Cover Change Detection in the Lower Jordan River (LJR), 1984-2016, Using GIS and RS

The objective of this study is to monitor and analyze the meandering, and changes in land use / land cover (LULC) caused by the large reduction of water flow of the lower Jordan River (LJR), resulting from climatic conditions, and conflict over water resources between Syria, Jordan, Israel and the Palestinian Authority in the upper part of the Jordan River Basin (JRB). These circumstances have led to dramatic decline in the Dead Sea level by a vertical distance of -39 m during the monitoring period. This has resulted in the scarcity of water resources, changes affecting the geomorphology of the river as well as the vegetated area and the spatial distribution of riparian vegetation in the (LJR). These changes were examined using Landsat TM, ETM, all images acquired in August 1984, 2000, and 2016, and a topographic map (TM) was used as a base map. The multi-temporal images were geometrically and radio metrically calibrated to each other and used as input for an automatic change detection procedure. The results of the interpretation showed that there was an elongation in the active channel length of about 741.8 m within the monitoring period as a result of the Dead Sea retreat, and about 2.65 km caused by meandering. The direction of the migration rates varied towards west and east, with the dominant direction towards the west and the annual average migration rate for west and east was 0.325 m, with a total lateral migration during the study period about only 17.875m in both directions west and east. River meandering has increased from 1.8 m to 2.1 m in the time period. With respect to (LULC), the difference image indicated that significant positive changes in green vegetation have occurred between 1984 and 2016; this is due to the expansion of water storage by canals, and dams in all riparian counters, with an increase in water ponds. The Normalized Difference Vegetation Index (NDVI) showed that the riparian vegetation area increased by 36.9% during the monitoring period, indicating the stability of the valley floor. DOI: http://dx.doi.org/10.5755/j01.erem.74.2.20917

Evaluating the effects of check dams on channel geometry, bed sediment size and riparian vegetation in Mediterranean mountain torrents

In mountain streams possible negative impacts of check dams on soil, water and riparian vegetation due to check dam installation can be noticed. In spite of the ample literature on the qualitative effects of engineering works on channel hydrology, morphology, sedimentary effects and riparian vegetation characteristics, quantitative evaluations of the changes induced by check dams on headwater characteristics are rare.In order to fill this gap, this study has evaluated the effects of check dams located in headwaters of Calabria (Southern Italy) on hydrological and geomorphological processes and on the response of riparian vegetation to these actions. The analysis has compared physical and vegetation indicators in transects identified around check dams (upstream and downstream) and far from their direct influence (control transects).Check dams were found to influence significantly unit discharge, surface and subsurface sediments (both upstream and downstream), channel shape and transverse distribution of riparian vegetation (upstream) as well as cover and structure of riparian complexes (downstream). The actions of the structures on torrent longitudinal slope and biodiversity of vegetation were less significant. The differences on bed profile slope were significant only between upstream and downstream transects. The results of the Agglomerative Hierarchical Cluster analysis confirmed the substantial similarity between upstream and control transects, thus highlighting that the construction of check dams, needed to mitigate the hydro-geological risks, has not strongly influenced the torrent functioning and ecology before check dam construction. Moreover, simple and quantitative linkages between torrent hydraulics, geomorphology and vegetation characteristics exist in the analysed headwaters; these relationships among physical adjustments of channels and most of the resulting characteristics of the riparian vegetation are specific for the transect locations with respect of check dams. Conversely, the biodiversity of the riparian vegetation basically eludes any quantitative relations with the physical and other vegetal characteristics of the torrent transects.

Application and evaluation of the HEC-RAS – riparian vegetation simulation module to the Sacramento River

Life cycles of riparian vegetation are substantially impacted by river flow regime, groundwater and morphodynamics. The polygon-based riparian vegetation simulation module (RVSM) was developed and integrated into HEC-RAS one-dimensional flow model to predict spatially-explicit seed germination, seedling establishment, plant growth and mortality in response to fluvial processes. The HEC-RAS – RVSM system was applied to the Sacramento River reach to evaluate its capability in modeling temporal and spatial changes of riparian vegetation and the interactions between flow and riparian vegetation dynamics. River hydraulics, groundwater level and five vegetation types of the study reach were simulated for the eight-year (1999–2007) period. Model results demonstrate that the HEC-RAS – RVSM system reproduced the coverage increase of cottonwood, riparian shrub, invasive species and grass as well as the coverage decrease in mixed forest over the eight-year. The RVSM was able to capture sites for cottonwood establishment observed on certain point bars. The modeled variations of cottonwood coverage in response to dynamic flow regime facilitated determining and managing environmental flow for riparian vegetation restoration. The height of capillary fringe and root growth rate were two key parameters influencing riparian vegetation distribution.

Quantifying the impacts of river hydrology on riparian vegetation spatial structure: Case study in the lower basin of the Tarim River, China

AbstractRiver hydrology largely determines the species composition and spatial distribution of riparian vegetation. However, it is difficult to determine the riparian vegetation spatial pattern that is only influenced by river hydrology due to the complex impacts of other influencing factors in field environments. We investigated the spatial structure of riparian vegetation in the lower basin of the Tarim River in hyper‐arid western China, where distinct geomorphic and climatic features exclude the influences of factors other than river hydrological factors on the spatial structure of riparian vegetation. Landsat 8 Operational Land Imager remotely sensed data were used to identify the different vegetation types and obtain the vegetation leaf area index (LAI) in the study area. Our results showed that the overall vegetation LAI exhibited a negative exponential declining trend with distance from the river, but this relationship was different for the different vegetation types, exhibiting a negative exponential relationship for the Populus woodlands and a Gaussian‐type relationship for the Tamarix shrublands. The average width of the riparian vegetation decreased along the river by a negative power function. The average vegetation LAI decreased linearly along the river. The quantitative data we obtained regarding the river‐induced variation in the riparian vegetation cover with the distance from the river channel would particularly be useful for modelling riparian vegetation dynamics and distributions.

Application and assessment of a dynamic riparian vegetation model to predict the spatial distribution of vegetation in two Japanese river systems

Riparian ecosystems which are highly sensitive for hydrological processes are being altered worldwide, largely because of anthropogenic activities that include the construction of dams, the afforestation of river basins and the mining of river gravel. During last 60years, many of the Japanese rivers have been severely forested, and the gravel habitats that were dominant before the 1950s no longer exist. The restoration of these habitats to their former condition to conserve the diversity associated with undisturbed gravel habitats is a growing concern. Therefore, the influences that alter these riparian habitats must be recognized, and the development of a management tool to predict possible changes and evaluate causes and effects is emerged. In this context the numerical models used to describe the riparian vegetation dynamics is important. Therefore, the objective of this study was to evaluate the application of a recently developed dynamic riparian model (DRIPVEM) under Japanese river conditions to predict the spatial distribution of riparian vegetation. The model simulation was conducted for two Japanese river reaches, and the compatibility of the model was verified with observations on the distribution of vegetation. Based on these visual observations, the simulated results showed reasonable agreement with the observations. Furthermore, the compatibility of the model was evaluated with the help of a GIS tool. The model compatibility was greater than 70% for the simulation of both tree and herb distributions; however, for the bare areas, the compatibility was approximately 50%. The accuracy of the model was greater than 0.85 and based on the Kappa coefficient of agreement, the performance of the model was moderate to substantial for the conditions of the two river systems. Although mimicking complex ecosystem processes is a challenging task for any type of dynamic model; the DRIPVEM has great potential to predict the distribution of riparian vegetation.

The Hydrological Regimes Brought by the Three Gorges Project Affected Riparian Vegetation Distribution and Diversity in 2009 and 2010

Post-dam riparian vegetations affected by the new hydrological regimes in the Three Gorges Reservoir (TGR) were investigated in 2009 and 2010, respectively. The investigation in 2009 showed that about 231 vascular plant species belonging to 169 genera of 61 families were distributed in the water-level-fluctuation zone (WLFZ) of the (TGR). Three vegetation types, including Chuanjiang, Gorge, and other vegetation types, were classified efficiently via cluster analysis. Alpha diversity analysis indicated that species richness gradually decreased with decreasing elevation. Beta diversity analysis indicated that high environment heterogeneity was existed between the lower section and the other two sections, and environment homogeneity was also existed between middle section and upper section. Using the analysis of the field growth in the 2009 and 2010 field surveys as bases, we proposed a list of perennial herb species and woody species that may potentially occurred in the WLFZ of the TGR. In addition, we predicted plant community structural changes in the different altitude sections of WLFZ in the future.

Analyzing Landscape Trends on Agriculture, Introduced Exotic Grasslands and Riparian Ecosystems in Arid Regions of Mexico

Riparian Zones are considered biodiversity and ecosystem services hotspots. In arid environments, these ecosystems represent key habitats, since water availability makes them unique in terms of fauna, flora and ecological processes. Simple yet powerful remote sensing techniques were used to assess how spatial and temporal land cover dynamics, and water depth reflect distribution of key land cover types in riparian areas. Our study area includes the San Miguel and Zanjon rivers in Northwest Mexico. We used a supervised classification and regression tree (CART) algorithm to produce thematic classifications (with accuracies higher than 78%) for 1993, 2002 and 2011 using Landsat TM scenes. Our results suggest a decline in agriculture (32.5% area decrease) and cultivated grasslands (21.1% area decrease) from 1993 to 2011 in the study area. We found constant fluctuation between adjacent land cover classes and riparian habitat. We also found that water depth restricts Riparian Vegetation distribution but not agricultural lands or induced grasslands. Using remote sensing combined with spatial analysis, we were able to reach a better understanding of how riparian habitats are being modified in arid environments and how they have changed through time.

Geomorphic predictors of riparian vegetation in small mountain watersheds

Aims Hydrogeomorphic processes operating at watershed, process zone and site scales influence the distribution of riparian vegetation. However, most studies examining the relationships between hydrogeomorphic processes and riparian vegetation are conducted at site scales. We quantified the relative importance of watershed, process zone and site geomorphic characteristics for predicting riparian plant community types and plant species abundances in four small mountain watersheds in central Nevada, USA. Methods We mapped riparian vegetation types and identified process zones (based on dominant geomorphic process and valley fill material) within the watersheds. We sampled sites in each combination of vegetation type and process zone (n = 184 sites) and collected data on watershed scale factors, valley and stream geomorphic characteristics and on plant cover of each geomorphic surface. Plant community types were defined by cluster and indicator species analyses of plant cover data, and related to geomorphic variables using ordination analysis (nonmetric multidimensional scaling). Linear mixed effects models were used to predict abundances of indicator species. Important Findings Variables describing position in the watershed (elevation, contributing area) that are related to gradients of temperature, moisture and stream discharge were of primary importance in predicting plant community types. Variables describing local geomorphic setting (valley width, stream gradient, channel sediments, geomor phic surface height) were of secondary importance, but accurately described the geomorphic setting of indicator species. The process zone classification did not include position in the watershed or channel characteristics and only predicted plant community types with unique geomorphic settings. In small mountain watersheds, predicting riparian vegetation distribution requires explicit consideration of scale and geomorphic context within and among water sheds in addition to site variables.

Effect of water table fluctuations on phreatophytic root distribution

The vertical root distribution of riparian vegetation plays a relevant role in soil water balance, in the partition of water fluxes into evaporation and transpiration, in the biogeochemistry of hyporheic corridors, in river morphodynamics evolution, and in bioengineering applications. The aim of this work is to assess the effect of the stochastic variability of the river level on the root distribution of phreatophytic plants. A function describing the vertical root profile has been analytically obtained by coupling a white shot noise representation of the river level variability to a description of the dynamics of root growth and decay. The root profile depends on easily determined parameters, linked to stream dynamics, vegetation and soil characteristics. The riparian vegetation of a river characterized by a high variability turns out to have a rooting system spread over larger depths, but with shallower mean root depths. In contrast, a lower river variability determines root profiles with higher mean root depths.

Effects of riparian vegetation on topographic change during a large flood event, Rio Puerco, New Mexico, USA

The spatial distribution of riparian vegetation can strongly influence the geomorphic evolution of dryland rivers during large floods. We present the results of an airborne lidar differencing study that quantifies the topographic change that occurred along a 12 km reach of the Lower Rio Puerco, New Mexico, during an extreme event in 2006. Extensive erosion of the channel banks took place immediately upstream of the study area, where tamarisk and sandbar willow had been removed. Within the densely vegetated study reach, we measure a net volumetric change of 578,050 ± ∼ 490,000 m3, with 88.3% of the total aggradation occurring along the floodplain and channel and 76.7% of the erosion focusing on the vertical valley walls. The sediment derived from the devegetated reach deposited within the first 3.6 km of the study area, with depth decaying exponentially with distance downstream. Elsewhere, floodplain sediments were primarily sourced from the erosion of valley walls. Superimposed on this pattern are the effects of vegetation and valley morphology on sediment transport. Sediment thickness is seen to be uniform among sandbar willows and highly variable within tamarisk groves. These reach‐scale patterns of sedimentation observed in the lidar differencing likely reflect complex interactions of vegetation, flow, and sediment at the scale of patches to individual plants.

Dynamic vegetation model as a tool for ecological impact assessments of dam operation

This study presented the results of an application of a floodplain dynamic model to the Nakdong River, South Korea. At the Nakdong River, high flows are reduced by dams and the river bed is degraded. Both changes contribute toward the same result: the floodplain is hydraulically disconnected from the main channel and the morphology of the river has been modified. Such changes brought also to a deep modification in the riparian vegetation distribution, abundance and composition. The focus of the study is on the relationship between the hydrology alterations induced by dams and the successional changes in riparian vegetation. More in detail, the study attempts to adapt an existing dynamic floodplain vegetation model to the Nakdong ecosystem characteristics in order to single out what were the effects of the dam operations that led to a change in the riparian landscape. The dynamic model is targeted on Monsoon floodplain vegetation, it is developed upon a custom developed geoprocessing framework and supported by a standalone user interface. It simulates dynamics of floodplain vegetation communities based on different physical parameters. The general concept of the model is that a vegetation community will either undergo toward a maturation stage or will be destroyed (recycling or retrogression) if the magnitude of key physical parameters is greater than the threshold value for a specific community. The model has been calibrated using hydraulic data spanning the time period 1952–2007. The calibration results have been also used to investigate the impacts on the riparian vegetation given by dams operations. The findings of the research highlight that consecutive years of reduced maximum discharge allowed consistent vegetation colonization of riverine areas that were bare before the dam construction.