In response to increasing concerns about the potential toxicological impacts of (extreme) flood events, scientists from several disciplines have joined to form the interdisciplinary research project named FLOODSEARCH. FLOODSEARCH is one of the recent Pathfinder Projects supported by the German Excellence Initiative via the Exploratory Research Space at RWTH Aachen (ERS). FLOODSEARCH aims to combine methodologies of hydraulic engineering and ecotoxicology in a new interdisciplinary approach to assess the risks associated with the remobilisation of particulate bound contaminants often observed after severe flood events. Impacts of extreme flood events and aspects of re-mobilisation of sedimentbound toxic compounds will be characterised and evaluated in controlled experiments fusing flood simulation technologies with biological effects assessment. The overall goal is to establish a novel and more realistic approach towards flood event testing that can be applied to a number of different questions and species. Specifically, model aquatic species such as rainbow trout (Onchorhynchus mykiss) will be exposed to particle-bound contaminants in flood-like conditions in a specifically designed annular flume that
Experimental model data are compared with numerical computations of dike-break induced flows, focusing on the final steady state. An idealized scale model was designed reproducing the specific boundary conditions of dike breaks. Discharges, water level, and depth profiles of horizontal velocities were recorded and validated by numerical modeling. The latter was performed by two different models solving the two-dimensional depth-averaged shallow water equations, namely a total variation diminishing Runge-Kutta discontinuous Galerkin finite element method, and a finite volume scheme involving a flux vector splitting approach. The results confirmed convergence and general applicability of both methods for dike-break problems. As regards their accuracy, the basic flow pattern was satisfactorily reproduced yet with differences compared to the measurements. Hence, additional simulations by the finite volume model were performed considering various turbulence closures, wall-roughnesses as well as nonuniform Boussinesq coefficients. RÉSUMÉDes données de modèles expérimentaux sont comparées aux calculs numériques des écoulements induits par les ruptures de digues, en se concentrant sur l'état d'équilibre final. Un modèle réduit idéalisé a été conçu pour reproduire les conditions aux limites spécifiques des ruptures de digues. Les débits, le niveau d'eau, et les profils verticaux des vitesses horizontales ont été enregistrés et validés par modélisation numérique. Le dernier a été réalisé par deux modèles différents résolvant les équations bidimensionnelles en eau peu profonde moyennées sur la hauteur, à savoir une méthode TVD (total variation diminishing) de Runge-Kutta Galerkin discontinue en éléments finis, et un schéma en volumes finis comportant un splitting du vecteur flux. Les résultats ont confirmé la convergence et l'applicabilité générale des deux méthodes pour les problèmes de rupture de digues. En ce qui concerne leur exactitude, la configuration de base de l'écoulement a été reproduite d'une manière satisfaisante avec cependant des différences par rapport aux mesures. C'est pourquoi, des simulations additionnelles ont été effectuées avec un modèle en volumes finis en considérant diverses fermetures de la turbulence, et rugosités de paroi, ainsi que des coefficients de Boussinesq non-uniformes.
This paper studies solid matter from a section of the A9 motorway, Kerault Region, France, used in a study of the effects of pollution. This study analyzed both settled sediments from collecting basin and characteristics of sediments in the water column during and after eight storm events between October 12, 1993, and February 6, 1994. Settled sediments were used to measure particle sizes, mineral content, and related characteristics, whereas water samples were used to document total suspended solids, mineral content, and heavy metals. Solid particles larger than 100 IJ-m in diameter are easily separated by simple settling, unlike particles smaller than 100 IJ-m in diameter, which remain in suspension in nmoff. To treat runoff, particles smaller than 50 IJ-m in diameter, which represent approximately three-quarters of the weight of the solids, must be studied. On average, 50% v/v of particles have a diameter less than 15.2 IJ-m, whereas the geometric mean is 12.6 IJ-m. Regarding sedimentation speed, from the eight rainfalls studied, 50% w/w of particles smaller than 50 IJ-m in diameter fall at a speed less than 2.98 m/h on average (results for the eight rainfalls vary from 2.5 to 3.3 m/h), and 50% of particles between 50 and 100 IJ-m in diameter fall at a speed less than 9.8 m!h on average (results of the eight rainfalls vary from 5.7 to 13.1 mIh). Thus, treatment of runoff entails separating or eliminating solid waste. Furthermore, measuring sedimentation speed of particles with diameters smaller than 100 IJ-m seems to be an essential stage in the design of treatment plants (Vignoles, 1991). Water Environ. Res .. 71, 398 (1999).
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