Observations and Modeling of Transverse Mixing in a Natural Gravel-Bed River
Journal Title: Journal of River Engineering - Year 2014, Vol 2, Issue 9
Abstract
A comprehensive, continuous, point-source, dye concentration experiment was performed on the Kootenai River, Idaho, USA to describe natural river transport and mixing dynamics. Centerline fluorescent dye concentration releases formed quasi-steady state plumes. Combinations of stationary and moving observational platforms were used to describe the dye concentration plume spreading and the velocity field throughout a 550 m study reach.Observational platforms included 13 fluorescent concentration sensors, 5 acoustic Doppler profiling current meters and one acoustic Doppler velocimeter. Natural channel transverse diffusivities are calculated using concentration measurements. Observed mixing is strongly controlled and dependent on channel features. Field observations are used to initialize and validate an open source, processed-based, three-dimensional (3D) hydrodynamic model (Delft3D-FLOW). Model simulations show good agreement with the in situ measurements with velocity fields (velocity magnitude R2=0.87), water levels (R2=0.97) and concentration spread. To examine the mixing processes, prominent bathymetric features of a constriction, riffle and embayment are isolated and idealized. The numerical investigations emphasize that linear superposition of channel feature concentration spread effects does not provide accurate overall spreading estimates. Accurate concentration spreading prediction required resolving complex coupled secondary velocity fields controlled by bathymetric variability at all scales. These coherent velocity structures are responsible for the observed spatial concentration distributions, which are shown to spatially enhance and restrict lateral transport, resulting in a strongly non-linear mixing response.
Authors and Affiliations
William Swick - Jamie MacMahan - Ad Reniers - Ed Thornton
Estimation of possible Flooding Risks for Enhancement in Flood Resilience in River Valleys
Flood is one of the major natural hazards which could cause great disaster. In order to enhance the flood resilience, the proper estimation of flood risks mainly possible loss of life is very much important. Catastrop...
Water Yield Estimation in Polrudwatershed Based on Empirical Methods and Modelling in Geographic Information System (GIS)
Accurate estimation of basin discharge has been discussed by the experts in various construction projects and this important issue has considerable influence on the design of the required structures and their cost. Ba...
Assessment and Quality Classification of Water in Karun, Dez and Karkheh Rivers
Rivers are assumed as one of the most important sources of water supply for agricultural, drinking and industrial uses. With this regard, quality evaluation of these sources is one of the main duties in the field of e...
3D Investigation of Flow Hydraulic in U Shape Meander Bendswith Constant, Decreasing and Increasing Width
In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since...
Numerical Simulation of the Angle of Groyne Installation on the Separation Zone Length Behind it
Groynes are usually installed along the river side and those are used for a lot of application such as bank protection. These structures would be changed the flow pattern and prevent bank erosion. So understanding tur...