River Management Practices Research Articles

Environmental heterogeneity affects input, storage, and transformation of coarse particulate organic matter in a floodplain mosaic

Quantifying spatial and temporal dynamics of organic matter (OM) is critical both for understanding ecosystem functioning and for predicting impacts of landscape change. To determine the influence of different habitats and coarse particulate OM (CPOM) types upon floodplain OM dynamics, we quantified aerial input, lateral surface transfer, and surface storage of CPOM over an annual cycle on the near-natural floodplain of the River Tagliamento in NE-Italy. Using these data, we modelled floodplain leaf dynamics, taking account of the spatial distribution and hydrologic connectivity of habitats, and using leaf storage as a response variable. Mean aerial CPOM input to the floodplain was similar from riparian forest and islands, but surface transfer was greater from islands, supporting the suggestion that these habitats act as “islands of fertility” along braided rivers. Leaves were the lateral conveyor of energy to more open parts of the floodplain, whereas CPOM was mainly stored as small wood in vegetated islands and riparian forest. Simulating the loss of habitat diversity (islands, ponds) decreased leaf storage on the whole floodplain, on exposed gravel and in large wood accumulations. In contrast, damming (loss of islands, ponds and floods plus floodplain overgrowth) greatly increased storage on exposed gravel. A random shuffle of habitats led to a storage increase on exposed gravel, while that in large wood accumulations and ponds declined. These results disentangle some of the complexities of CPOM dynamics in floodplain ecosystems, illustrate the value of models in understanding ecosystem functioning at a landscape level, and directly inform river management practice.

The Thames flood series: a lack of trend in flood magnitude and a decline in maximum levels

The flow series for the River Thames near its tidal limit is one of the most studied in the world. Its length and completeness, and the richness of the historical information which augments the formal flow record, ensures that the series is of immense value. However, the variability in flood magnitude and frequency that it captures needs to be interpreted with caution. The homogeneity of the time series is influenced by a wide range of factors, including changes in the hydrometric capability of the gauging station and the impact of differing water, river and land management practices on the flow regime. Nevertheless, both the daily flow series and the record of lock levels provide some reassuring signals regarding the resilience of the Thames to fluvial flood risk in a warming world. Since routine flow measurement began in 1883, the Thames basin has seen a substantial rise in air temperature and a tendency for both winter rainfall and annual runoff to increase. There is no trend in fluvial flood magnitude however, partly reflecting a decline in snowmelt contributions to major floods and annual maximum lock levels show a significant decline, reflecting a highly sustained programme of river management.

Quantification of uncertainty in design water levels due to uncertain bed form roughness in the Dutch river Waal

AbstractHydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modelling of river processes involves numerous uncertainties, resulting in uncertain model results. Knowledge of the type and magnitude of these uncertainties is crucial for a meaningful interpretation of the model results. Uncertainty in the hydraulic roughness due to bed forms is one of the main contributors to the uncertainty in the modelled water levels. The aim of this study was to quantify the uncertainty in the bed form roughness under design conditions and quantify the effect on the design water levels in the Dutch river Waal. Five roughness models that predict bed form roughness based on measured bed form and flow characteristics were extrapolated to design conditions. The results show that the 95% confidence interval of the predicted Nikuradse roughness values under design conditions ranges from 0.32 to 1.03 m. This uncertainty was propagated through the two‐dimensional hydrodynamic model, WAQUA, by means of a Monte Carlo simulation for an idealized schematization of the Dutch river Waal. The uncertain bed form roughness results in an uncertainty in the design water levels, with a 95% confidence interval of 0.53 m, which is significant for Dutch river management practice. The uncertainty in the bed form roughness was mainly caused by a lack of knowledge about the physical process of bed form evolution that causes roughness. An improved estimation of bed form roughness can significantly reduce the uncertainty in the design water levels. Copyright © 2012 John Wiley & Sons, Ltd.

Understanding multiple ecological responses to anthropogenic disturbance: rivers and potential flow regime change

Human-induced alteration of the natural flow regime is a major threat to freshwater ecosystems and biodiversity. The effects of hydrological alteration on the structural and functional attributes of riverine communities are expected to be multiple and complex, and they may not be described easily by a single model. Based on existing knowledge of key hydrological and ecological attributes, we explored potential effects of a flow-regulation scenario on macroinvertebrate assemblage composition and diversity in two river systems in Australia's relatively undeveloped wet-dry tropics. We used a single Bayesian belief network (BBN) to model potential changes in multiple assemblage attributes within each river type during dry and wet seasons given two flow scenarios: the current, near-natural flow condition, and flow regulation. We then used multidimensional scaling (MDS) ordination to visually summarize and compare the most probable attributes of assemblages and their environment under the different scenarios. The flow-regulation scenario provided less certainty in the ecological responses of one river type during the dry season, which reduced the ability to make predictions from the BBN outputs directly. However, visualizing the BBN results in an ordination highlighted similarities and differences between the scenarios that may have been otherwise difficult to ascertain. In particular, the MDS showed that flow regulation would reduce the seasonal differentiation in hydrology and assemblage characteristics that is expected under the current low level of development. Our approach may have wider application in understanding ecosystem responses to different river management practices and should be transferred easily to other ecosystems or biotic assemblages to provide researchers, managers, and decision makers an enhanced understanding of ecological responses to potential anthropogenic disturbance.

DISTRIBUTION AND HABITAT USE OF THE MISSOURI RIVER AND LOWER YELLOWSTONE RIVER BENTHIC FISHES FROM 1996 TO 1998: A BASELINE FOR FISH COMMUNITY RECOVERY

ABSTRACTPast and present Missouri River management practices have resulted in native fishes being identified as in jeopardy. In 1995, the Missouri River Benthic Fishes Study was initiated to provide improved information on Missouri River fish populations and how alterations might affect them. The study produced a baseline against which to evaluate future changes in Missouri River operating criteria. The objective was to evaluate population structure and habitat use of benthic fishes along the entire mainstem Missouri River, exclusive of reservoirs. Here we use the data from this study to provide a recent‐past baseline for on‐going Missouri River fish population monitoring programmes along with a more powerful method for analysing data containing large percentages of zero values. This is carried out by describing the distribution and habitat use of 21 species of Missouri River benthic fishes based on catch‐per‐unit area data from multiple gears. We employ a Bayesian zero‐inflated Poisson model expanded to include continuous measures of habitat quality (i.e. substrate composition, depth, velocity, temperature, turbidity and conductivity). Along with presenting the method, we provide a relatively complete picture of the Missouri River benthic fish community and the relationship between their relative population numbers and habitat conditions. We demonstrate that our single model provides all the information that is often obtained by a myriad of analytical techniques. An important advantage of the present approach is reliable inference for patterns of relative abundance using multiple gears without using gear efficiencies. Copyright © 2011 John Wiley & Sons, Ltd.

An equation for bed-load transport capacities in gravel-bed rivers

Summary Detailed hydraulic and sedimentary information is needed to accurately predict bed-load transport rates in natural gravel-bed rivers. Yet, being able to estimate maximum transport rates from simple measurements would greatly benefit various sediment-related river management practices. To this end, a new concept of bed-load transport capacity for heterogeneous grains in gravel-bed rivers was introduced as the maximum possible transport rate a gravel-bed river can have for a given value of dimensionless shear stress, calculated using the median size of bed-load grains. Flows that can transport bed load at capacity may be identified by the criterion that the median size of bed-load grains must be greater than or equal to that of the bed substrate. Then, a single coefficient, power equation was developed to predict such capacities using bed-load capacity data covering both low flows with an armor layer and high flows without it. The good performance of this empirical equation was confirmed by comparing its predictability with that of Mayer Peter and Muller’s and Bagnold’s bed-load equations. Using an independent data compiled from six gravel-bed rivers in Idaho, not only was the empirical equation validated but also the criterion for identifying the condition under which bed load is transported at capacity was tested. In practice, the empirical equation can be used to estimate the maximum possible bed-load transport rates during high flow events, which is useful for various sediment-related river managements.

The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed.

Substrate requirements of spawning Chinook salmon (Oncorhynchus tshawytscha) are dependent on local channel hydraulics

AbstractMicro‐scale (<0.1 channel widths) physical conditions within channels ultimately exert a strong control on habitat selection by fish species. Data are presented demonstrating that micro‐habitat requirements of spawning Chinook salmon (Oncorhynchus tshawytscha) are strongly inter‐related; fish utilized coarser substrate if associated with faster flow velocities. This was not observed to be controlled through a hydraulic sorting mechanism but, rather, related to the physical processes of spawning. Failure to consider the ‘elastic’ nature of Chinook salmon spawning requirements resulting from links between the physical parameters may have implications for river management practices such as restoration or setting environmental flows. Copyright © 2009 John Wiley & Sons, Ltd.

Hydromorphology and land use at different spatial scales: expectations in a changing climate scenario for medium-sized rivers of the Western Italian Alps

The study presents an investigation of the relationships between hydromorphological features and land use in two medium-sized Italian Alpine catchments. The South European River Habitat Survey (SE_RHS) method was applied in the collection of hydromorphological data. Five different spatial scales ranging from catchment to site scale were considered for the quantification of land use. Separate Principal Component Analyses for grouped data sets were run on hydromorphological variables related to different spatial scales and the type of information provided. The analyses demonstrated that the most important gradients are related to channel stability. Unstable river reaches, characterized by a significant presence of unvegetated bars, were predominantly related to natural land use. On the contrary, more stable river reaches, characterized by the presence of vegetated bars, were found to be related to anthropogenic land use. High turbulence flow types appeared to be associated with urban and industrial land use. The climate scenario predicts a general increase in temperature, a slight decrease in precipitation, a more dynamic discharge regime and an increase in extreme events, all of which may produce considerable modifications to present agricultural and river management practices. A conceptual model based on the situation observed in the studied catchments is presented, that can be used to infer possible land use changes, during climate variation, in areas adjacent to rivers.

Chronology of Sediment Nutrient Geochemistry in Apalachicola Bay, Florida (U.S.A)

Land use changes have been shown to alter the balance of nutrient and mineral sources and sinks to coastal systems. These shifts are often preserved in sediment records. In Apalachicola Bay, productivity is dependent on nutrient loading from the Apalachicola-Chattahoochee-Flint (ACF) river basin; alterations to ACF watershed flow by management activities coupled with increased marine water inundation associated with rising sea level threaten this productivity. The objective of this research was to evaluate past changes in nutrient loading to Apalachicola Bay as recorded in sediment history and determine if these changes could be associated with both anthropogenic and natural alterations in the system. Sediment cores from three sites in the bay were collected and analyzed for organic carbon (C), total nitrogen (N), and total phosphorus (P) concentrations and δ13C and δ15N stable isotopic abundances. The three sites are located at the river mouth (S1), mid-bay (S2), and in the northeastern region of the bay (S3). Carbon and nitrogen concentrations, ratios, and stable isotopes coupled with grain-size shifts for the bay suggest a decrease in river organic matter supply and a change in sediment clay content supply and/or distribution for the bay. Overall, the applied indicators suggest an increase in marine influence on the organic matter in the estuary. These shifts appear to be associated with Apalachicola River management practices coupled with sea-level rise in the Gulf of Mexico.

New Databases Reveal 200 Years of Change on the Mississippi River System

Over the past two centuries, the Mississippi River system (MRS) has been dramatically altered to facilitate commercial navigation and provide flood control. Because of its long history of modification, rigorous measurements including maps, charts, surveys, and other data concerning the MRS are available from the past 200 years or longer. Comparison between historical reference conditions and modern conditions can document changes related to natural processes, human impacts, and river management practices and policies.To show these changes, we have assembled a hydrologic database of approximately 7 million measurements and a geospatial database consisting of 4878 map sheets dating back to 1765. The databases include nearly all available data sources for the navigable Mississippi River, the lower Missouri River, and the Illinois River (>4500 kilometers of waterways; see Figure 1, in the electronic supplement to this Eos issue; http://www.agu.org/eos_elec). We have digitized all 81 map sets and georeferenced 48 of those map sets, meaning that the maps have been referenced in physical space for use in a geographic information system. The purpose for constructing these databases is to centralize and standardize these data sources and to make them broadly available for research and management. In this article we describe the data, the databases, and their dissemination.

Objectives of public participation: Which actors should be involved in the decision making for river restorations?

River restoration as a measure to improve both flood protection and ecological quality has become a common practice in river management. This new practice, however, has also become a source of conflicts arising from a neglect of the social aspects in river restoration projects. Therefore appropriate public involvement strategies have been recommended in recent years as a way of coping with these conflicts. However, an open question remains: Which stakeholders should be involved in the decision‐making process? This, in turn, raises the question of the appropriate objectives of public participation. This study aims to answer these questions drawing on two case studies of Swiss river restoration projects and a related representative nationwide survey. Our findings suggest that public involvement should not be restricted to a small circle of influential stakeholder groups. As restoration projects have been found to have a substantial impact on the quality of life of the local population, avoiding conflicts is only one of several objectives of the involvement process. Including the wider public provides a special opportunity to promote social objectives, such as trust building and identification of people with their local environment.

Habitat characteristics and the distribution of Odonata in a lowland river catchment in eastern England

The influence of habitat characteristics on the distribution of larval and adult Odonata communities in a lowland river in eastern England was studied. There was a longitudinal distribution of Odonata, with larval assemblages being influenced directly by marginal flow velocity, biochemical oxygen demand (BOD) and phosphate concentrations and indirectly by shade and cover of floating vegetation. Adult populations responded directly to shade, reed cover, amenity-managed land use and bank height, and indirectly to BOD and ammonia concentrations. Distribution patterns were strongly associated with both natural changes along the river system and management impacts. River management practices locally disrupted the natural displacement of species along the river, but whilst some forms of human interference on river systems were beneficial to species richness, the effects on stenotopic species were disadvantageous. To conserve Odonata management emphasis should be on the maintenance of suitable conditions for river specialists.

Geomorphic Disturbance and its Impact on Darter (Teleostomi: Percidae) Distribution and Abundance in the Pearl River Drainage, Mississippi

We examined channel and point bar changes over time in the Pearl River, a meandering, Coastal Plain stream in Mississippi and Louisiana. We interpreted extreme changes in bar area as evidence of channel instability and related this to the diversity and abundance of darters in the river. Darters were less diverse and abundant in more disturbed reaches in comparison with relatively undisturbed reaches. Darter abundance was positively correlated with proximity to extreme bar-area changes. The relationship between channel instability and darter abundance observed here points to the importance of landscape level approaches to in-stream habitat management. The results suggest that river management practices that prevent or mitigate extreme changes in channel or sediment dynamics should be adopted for the benefit of benthic communities.

Valley floor landscape change following almost 100 years of flood embankment abandonment on a wandering gravel‐bed river

AbstractCritical to restoring the nature conservation value of many river corridors is an understanding of how alluvial landscapes will respond to cessation of river management and land use practices that have previously degraded the environment. This paper analyses changes in valley floor landforms and vegetation patch dynamics, in relation to fluvial disturbance, over a period of almost 100 years following flood embankment abandonment on a wandering gravel‐bed river, namely the River Tummel, Scotland. Such rivers were once typical of many draining upland areas of northern maritime Europe. Prior to abandonment the valley floor landscape was agriculturally dominated and the river for the most part was single thread confined between flood embankments. The pattern of landform change and vegetation patch development over time following a decision in 1903 not to maintain embankments was tracked by geomorphic and land cover mapping utilizing successive sets of aerial photography for the period 1946 to 1994. A historical context for these changes was also feasible because the channel planform in 1900 and earlier channel planform changes dating back to 1753 were known due to the availability of old maps and earlier geomorphic studies. The land cover mapping was validated by comparison of results produced from the interpretation work on the 1994 aerial photographs with the field‐based UK National Vegetation Classification protocol. The findings of the study illustrate that bordering the River Tummel fluvial landforms and vegetation patch mosaics, presumably resembling those that occurred before valley floor land use intensification, evolved in less than 50 years after flood embankment abandonment with a resultant increase in habitat diversity. The change relates primarily to flood‐induced channel planform change and moderate levels of fluvial disturbance. The general significance of this change to plant species diversity on the valley floor of the River Tummel and elsewhere is discussed as is possible implications of the upstream impoundment and scenarios for climatically induced changes in flood frequency and magnitude. The overall outcome is the strong possibility that simple changes in river management and land use practices could result in re‐establishment of the nature conservation value of similar river corridors in Europe over the medium term without active restoration efforts. Copyright © 2002 John Wiley & Sons, Ltd.

Sediment budgeting techniques in gravel-bed rivers

Abstract The difficulties in obtaining reliable sediment transfer data from direct field measurement or from sediment transport formulae are widely recognized by geomorphologists and river engineers. Quantifying morphological changes (erosion and deposition) in rivers by the analysis of archive data or by field survey, however, can overcome many of these difficulties and provide a mechanism by which sediment budgets can be calculated over a variety of spatial and temporal scales. This paper applies three sediment budgeting methods based on morphological changes in a hypothetical braided reach. These methods range from a simple two-dimensional planform budget to more sophisticated three-dimensional cross-profile and morphological budgets. The development of each budget technique is described and the limitations and applicability of each identified. The three methods are then used to calculated sediment transfer rates in a multi-thread reach on the River Severn in mid-Wales, UK. Results show that across four budget periods spanning 2.5 years the reach was a net exporter of sediment. Application of the planform budget to eight time periods since 1836 shows a similar pattern of net sediment export in the nineteenth century, but during the majority of the twentieth century the reach was a net sediment sink. Finally, the applicability of applying budgeting techniques to extended centennial and millennial timescales is discussed and an assessment made of the role they might play in advancing our understanding of Holocene river dynamics and informing sustainable river management practices.

Long-term variations in discharge capacity related to river management practice in Danish lowland streams

Long-term variations in discharge capacity related to river management practice in Danish lowland streams

Informing river management policies and programs with science

Conventional wisdom has it that we already have enough science to address the problems causing degradation of our environment, including rivers. This is not true. However it is the case that we could be using existing knowledge better, and that we could be doing more to learn the lessons from the huge sums being spent on river restoration and management. Informing good policy and practical on-ground management with R&D outputs has proven to be is difficult, but essential. This paper reviews some of the history of water and river management in Australia and how perceptions of rivers have evolved. It discusses the challenge of enhancing the linkages between science, policy and practice in river management. It outlines the knowledge exchange, R&D and capacity building strategies of the National Rivers Consortium--a new initiative whose founding partners are LWRRDC, the MDBC, CSIRO Land and Water and the Western Australian Waters and Rivers Commission. This strategic collaboration between policy makers, river managers and scientists brings together organisations with responsibility and expertise to improve the health and management of Australian rivers. The National Rivers Consortium is making a major investment in knowledge exchange and capacity building, based on direct personal contact and learning by doing. The Consortium is establishing a program of training activities targeting river managers and policy makers, based on the best available science and high quality information products. It will support river managers as they plan and implement river restoration and protection projects. The paper concludes with a discussion of the key knowledge gaps that remain impediments to the better management of Australia's unique and diverse river landscapes.

Hydrodynamics as a Major Factor Controlling the Occurrence of Green Macroalgal Blooms in a Eutrophic Estuary: A Case Study on the Influence of Precipitation and River Management

Data on the variation of physicochemical parameters, biomass and growth of green macroalgae (mostlyEnteromorpha ) collected between January 1993 and January 1997 in the Mondego Estuary (western coast of Portugal) was analysed with the aim to identify the factors that control opportunistic macroalgal abundance in the system.The annual biomass of Enteromorpha spp. is strongly dependent on the amount of fresh water that enters the system during winter and spring. In turn, the input of fresh water is regulated by precipitation and by river management practices. The optimization of the rice crops from the upstream valley depends on their water level, which determines the number of days and hours per day during which sluice gates remain open in winter and spring. River flow has significant impacts on salinity, N:P ratios, current velocities and light extinction coefficients within the system. The interaction of all these factors controls macroalgal growth and biomass loss processes.In winters and springs during which sluice gates are often closed due to water deficiency of the rice fields (dry winter and spring or dry winter followed by rainy spring), little fresh water enters the system and consequently, salinity remains high, N:P ratios around 20, light penetration increases, and current velocities fall. These conditions facilitate macroalgal fixation, enhance their growth and spring blooms occur. On the contrary, during winters and springs when fresh water is in excess of rice fields' needs (rainy winters and springs), sluice gates remain open for long periods of time. High input of fresh water to the system causes salinity and light penetration to decrease, while N:P ratios and current velocities increase. These conditions contribute both to reduced Enteromorpha growth and higher loss of macroalgal biomass from the system to the ocean.The present work shows that the inter-annual variation of macroalgal biomass in the Mondego Estuary is controlled by hydrodynamics, which in turn depends on precipitation and on river management, according with the water needs of the upstream rice crop.

Le Drac dans l'agglomération de Grenoble : première évaluation des changements géomorphologiques contemporains

Abstract : The Drac river in the Grenoble urban area : a first assessment of present-day geomorpholo- gical changes. Since the Second World War, the Drac river has been subject to considerable channel instability in its passage through the alluvial plain of Grenoble. Between 1950 and 1975, channel width decreased markedly and the river lowered its bed by more than 3 metres. A second phase began after 1975, when the channel became more stable and gravel bars became progressively covered by vegetation. Geomorphological changes in the alluival plain of Grenoble have been caused mainly by gravel extraction which between 1955 and 1972 accounted for more than 7 million m3. The effect of such extraction activities has been reinforced by water diversions near hydropower plants and by road construction works encroaching on the river channel. The complex response of fluvial systems to human activities requires that river management practices be continually updated.