inscription
PORTAIL D'INFORMATION GÉOGRAPHIQUE

Résultats de la recherche (4459 résultats)

Affinez votre recherche

Par Collection Par Auteur Par Date Par Sujet Par Titre
  • Critical flow in rockbed streams with estimated values for Manning's n - Comment and reply
  • Hydrodynamics ; Slope gradient ; Stream ; Stream flow
  • H. Chanson comments some aspects of the Tinkler's paper (1997) regarding critical flow, critical slope calculations and boundary shear stress distributions in undular flows, and K.J. Tinkler replies in turn.
  • Flow structure at an asymmetrical stream confluence
  • Carrying capacity ; Confluent ; Fluvial hydrology ; Hydrodynamics ; Illinois ; Stream ; Stream flow ; United States of America ; Water temperature
  • This research demonstrates how time-averaged downstream and cross-stream velocity fields at an asymmetrical stream confluence vary with changes in the momentum flux ratio and the combined (total) discharge of the confluent tributaries. In particular
  • , the study focuses on patterns of flow separation, flow convergence/divergence, and secondary circulation immediately downstream from the confluence, and the relationship of these patterns to the mixing interface between the combining flows.
  • Using simulated emergent vegetation to alter stream flow direction within a straight experimental channel
  • Channel geometry ; Experimentation ; Meander ; Mississippi ; Riparian vegetation ; Stream ; Stream flow ; United States of America ; Vegetation
  • The aim of this study was to induce the location of the maximum surface velocity or thalweg of a straight, degraded stream channel to meander through the use of managed emergent vegetation. This study showed that flow velocity can be markedly
  • reduced within and near the vegetation zones, flow can be diverted toward the opposite bank, and vegetation density can control the magnitude of these effects. The following discussion will focus on design considerations for stream restoration
  • Time-averaged flow structure in the central region of a stream confluence : a discussion
  • Channel geometry ; Confluent ; Fluvial hydrology ; Methodology ; Numerical model ; Stream ; Stream flow
  • This paper is a discussion of Rhoads and Kenworthy (1998) Time-averaged flow structure in the central region of a stream confluence, Earth Surface Processes and Landforms, 23, 171-191, that focuses upon the methods to identify secondary circulation
  • in river channel confluences. It argues that the use of the Rozovskii method can result in misleading conclusions about the nature of flow processes in confluences.
  • Time-averaged flow structure in the central region of a stream confluence
  • Carrying capacity ; Channel geometry ; Confluent ; Fluvial dynamics ; Fluvial hydrology ; Illinois ; Runoff ; Stream flow ; United States of America
  • This paper examines the time-averaged, two-dimensional (downstream and cross-stream) flow sructure within the central region of the confluence hydrodynamic zone (CHZ) at a small stream confluence with an asymmetrical planform. It also examines how
  • flow structure in this part of the CHZ varies with changes in hydrologic conditions and bed morphology. A particular focus is to document the presence or absence of time-averaged, helical motion in the central region of the confluence.
  • Flow disturbance caused by cross-stream coarse woody debris
  • Canada ; Channel geometry ; Hydraulic works ; Ontario ; River bed ; Roughness ; Spatial analysis ; Stream ; Stream flow ; Turbulence ; Wood
  • The aim of this study is to identify the spatial extent of flow disturbance caused by coarse woody debris positioned normal to the flow between 75° and 105°to the downstream flow direction. A reprsentative reach of the Pine River, Ontario, was used
  • The comparison of chinese and european stream runoff
  • Agriculture ; Annual variation ; China ; Europe ; Interannual variability ; Runoff ; Stream ; Stream flow ; Water balance ; Watershed
  • This paper compares stream runoff in China in terms of drainage basin, water balance, and regional distribution and regime of stream runoff with that in Europe. These comparative studies have been done in order to deepen the understanding
  • of regional differentiation and the cause of formation of stream runoff in both regions.
  • An evaluation of methods for estimating Manning's n in small mountain streams
  • Alaska ; Discharge ; Flow ; Hydrodynamics ; Mountain ; Roughness ; Stream ; Torrent
  • None of the 11 techniques used for estimating Manning's roughness coefficient in a small mountain stream in Alaska proved suitable. More accurate methods are needed for estimating flow velocities in steep mountain streams with large-scale roughness
  • Biogenic process ; Biogeography ; Dam ; Fluvial processes ; Montana ; National park ; Rodent ; Sediment budget ; Sedimentation ; Stream ; Stream flow ; United States of America
  • This study provides additional data on sedimentation and stream flow in order to better understand the efficacy of beaver dams to trap sediment and alter the flow regime of streams, respectively. Data are collected on sedimentation depth (thickness
  • ) and volume, as well as stream velocity and discharge above and below beaver dams in eastern Glacier National Park (GNP), Montana. In addition, measurements of dam and pond morphology are examined in relation to sedimentation and flow alteration patterns.
  • Velocity and flow resistance in step-pool streams
  • Channel geometry ; Discharge ; Experimentation ; Grain size distribution ; Longitudinal section ; Microrelief ; Runoff ; Stream ; Stream flow
  • The AA. present hydraulic measurements and calculations from 6 step-pool reaches of natural streams and from flume experiments dynamically similar to the prototypes. They aim to determine how rapidly flow resistance decreases, and velocity increases
  • A comparison of flow intensities in alluvial rivers : characteristics and implications for modelling flow processes
  • Forecast ; Least squares method ; Linear regression ; Methodology ; Model ; Stream ; Stream flow ; Turbulence
  • This paper compares flow intensity data obtained with different instruments from a variety of fluvial environments. It examines associations between the root-mean-square of longitudinal velocity fluctuations (flow intensity), local mean velocity
  • , relative depth, and boundary resistance. Preliminary approaches to prediction and modelling of variations in flow intensity are suggested based upon linear regression relationships.
  • Influence of experimental removal of large woody debris on spatial patterns of three-dimensional flow in a meander bend
  • Channel geometry ; Experimentation ; Meander ; Midwest ; Model ; Stream ; Stream flow ; United States of America
  • This study reports the results of a large woody debris (LWD) removal experiment in a meander bend along a low-energy stream in the Midwestern United States. The results indicate that the LWD obstruction influenced 3D flow structure in this bend
  • at all flow stages. After the removal of LWD from the bend, both downstream and secondary velocities increased and, though still weak, secondary flow intensified.
  • A stability criterion inherent in laws governing alluvial channel flow
  • Carrying capacity ; Channel geometry ; Mathematical hydrology ; Runoff ; Sediment transport ; Stream ; Stream flow
  • The stability criterion of maximum flow efficiency (MFE) has previously been found inherent in typical alluvial channel flow relationships, and this study investigates the general nature of this criterion using a wider range of flow resistance
  • and bedload transport formulae. This study provides support for the use of the criteria of MFE, maximum sediment transporting capacity and minimum stream power for understanding the operation of alluvial rivers, and also addresses limitations to the direct
  • Visualization of the turbulent flow structure in a gravel-bed river
  • Canada ; Hydrodynamics ; Model ; Programming ; Rocky Mountains ; Stream ; Stream flow ; Turbulence
  • A novel technique for visualizing turbulent flow data from a gravel-bed river is presented. The time development of flow velocity and shear stress at three heights is displayed using a computer program. This can be used to observe how
  • the fluctuations of velocity and shear stress interact both spatially and temporally. The AA. highlight examples of flow events which are important for the understanding of flow dynamics.
  • Secondary flow in anabranch confluences of a braided, graveled-bed stream
  • Alberta ; Canada ; Confluent ; Discharge ; Flow ; Fluvial dynamics ; Fluvial hydrology ; Ground survey ; Hydrodynamics ; Low water ; Stream
  • This paper reports the results of field measurements made with the objective of documenting the primary (downstream) and secondary (cross-stream) flow fields. Measurements of the velocity components were made in two, active, braided river anabranch
  • Hydrological analysis of flow variation of the Gila River in Safford Valley, southeast Arizona
  • Arizona ; Climatic variation ; Discharge ; Flood ; Fluvial hydrology ; Precipitation ; Stream ; Stream flow ; United States of America ; Water management
  • This paper investigates the temporal variations in flow of the Gila River in southeastern Arizona and investigates the relative influence of climate and land management on the runoff dynamics of the river.
  • Flow structure and development of circular meander pools
  • Channel geometry ; Fluvial erosion ; Fluvial hydrology ; Longitudinal section ; Meander ; New York State ; Stream ; Stream flow ; United States
  • In this study, flow structure, patterns of erosion and deposition, and bank strength in a circular meander pool are examined in order to understand better the conditions that lead to their development. Several possible modes of development
  • The effect of bed mobility on resistance to overland flow
  • Carrying capacity ; Channel geometry ; Experimentation ; Fluvial dynamics ; Runoff ; Stream ; Stream flow
  • The data for this study come from 54 flume experiments with fixed beds and 38 with mobile beds. The results imply that mobile beds offer greater resistance to flow than do fixed beds. Grain collisions with mobile beds are less elastic than those
  • Hydraulic geometry and maximum flow efficiency as products of the principle of least action
  • Carrying capacity ; Channel geometry ; Concept ; Stream ; Stream flow
  • . The theoretical results obtained here demonstrate that maximum flow efficiency (MFE) determines stable alluvial channel geometry and that this is a product of both maximum sediment transporting capacity (MSTC) and minimum stream power (MSP). Furthermore
  • This study finds that by introducing a channel form factor (width/depth ratio), the self-adjusting mechanism of alluvial channels can be illustrated directly with the basic flow relations of continuity, resistance and sediment transport
  • Spatial-temporal differences in in-stream flow requirement based on GIS : a case study of Yan'an region, northern Shaanxi
  • China ; Flood ; Geographical information system ; Sediment transport ; Semi-arid area ; Shaanxi ; Stream ; Stream flow ; Water resources
  • for measuring in-stream flow requirement has been put forward supported by experiential models and GIS spatial analysis. Additionally, the changes of in-stream flow requirement for environment and economic development have been addressed from spatial-temporal