Simulating Shallow Water Flows over Complex Topography Using a Well-Balanced And Positivity Preserving Central Scheme

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

A Gis-Based Decision Support System for Integrated Management of Agricultural Watersheds

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

REPRESENTATION OF DAM-BREACH GEOMETRY ON A REGULAR 2-D MESH USING QUADTREE LOCAL MESH REFINEMENT

Summary. A 2D first order upwinding finite-volume scheme is used on a regular orthogonal mesh in a numerical model to simulate dam break and dam breach flow from a reservoir. The discharge through the changing breach geometry is crucial to the accuracy of the resulting flood wave, yet the method of representing the breach by changing the bottom elevation of individual cells within the vicinity of the dam makes the breach hydrograph and peak discharge highly dependent on the mesh size and dam orientation. To increase accuracy and reduce computational burden associated with refining the entire mesh, a quadtree local mesh refinement technique was used to better model the dam breach geometry. Simulation results from the model using a combined regular and quadtree mesh showed that a coarse mesh with local refinement can yield a good approximation of the discharge hydrograph obtained using a globally-refined mesh, with significant savings in computational time

An Enhanced Two Dimensional Numerical Model for Simulating Floods Due to Dam And Levee Break/Breaching

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Bed shear stress estimation for gravity currents performed in laboratory

Gravity currents are caused by density differences between two fluids which may be due to temperature, dissolved substances or the presence of particles in suspension. In this study saline currents, in which the higher density is produced by dissolved salt, are reproduced in laboratory with the aim to characterize the bed shear stress. Saline currents can in fact be responsible for high erosion rates and the bed shear stress is a quantification of this erosive capacity. The dynamics of buoyancy driven flows are complex and the effect of the initial density gravity current on the bed shear stress is not explored yet. The results herein showed confirm the importance of detailed velocity profile measurements for the determination of the friction velocity which is a key parameter for the currents propagation and for characterizing the momentum and mass exchanges between the current and the bed. The spatial evolution of the bed shear stress caused by the passage of a gravity current is here estimated using the logarithmic velocity profile method for, as a first attempt, a value of the von Kármán constant of k 0.405. The use of this constant is then verified and discussed

Simulation and control of morphological changes due to dam removal in the Sandy River, Oregon, USA

A one-dimensional channel evolution simulation model (CCHE1D) is applied to assess morphological changes in a reach of the Sandy River, Oregon, USA, due to the Marmot Dam removal in 2007. Sediment transport model parameters (e.g. sediment transport capacity, bed roughness coefficient) were calibrated using observed bed changes after the dam removal. The validated model is then applied to assess long-term morphological changes in response to a 10-year hydrograph selected from historical storm water records. The long-term assessment of sedimentation gives a reasonable prediction of morphological changes, expanding erosion in reservoir and growing deposition immediately downstream of the dam site. This prediction result can be used for managing and planning river sedimentation after dam removal. A simulation-based optimization model is also applied to determine the optimal sediment release rates during dam-removal that will minimize the morphological changes in the downstream reaches

Application of Image Processing in Unsteady Flows to Investigate Bed Load Transport

Image processing is a promising technique to investigate bed load characteristics and its movement which has been applied in steady flow conditions for the last few decades. In this study, it is aimed to perform experiments in unsteady flows through generating a hydrograph to apply this technique and calculate the bed load transport. The sediment motion is recorded by a video recorder. The video records are analyzed by image processing techniques to determine the number and area of active grains moving at any instant as well as the average velocity of the grains. A bed load transport formula is introduced particularly used by the digital video analysis in which the time variation of the bed load due to the hydrograph could be precisely determined. It is revealed that the bed load determined at two sections of the flume is in accord and the bed load time curve has a fluctuating character