A distorted physical model to study sudden dam break flows

A distorted physical model, based upon Urkmez Dam in Izmir, Turkey, was built to study sudden dam break flows. The distorted model had a horizontal scale of 1/150 and vertical scale of 1/30, containing dam reservoir, dam body and downstream area—from dam body to Urkmez urban area until the sea coast. In the model, the reservoir is approximately 12 m3, the dam body has a width of 2.9 m and a height of 1.1 m and the downstream area is nearly 200 m2. The Ürkmez dam is chosen since it has reasonable dimensions and it is located close to Ürkmez village. The features creating roughness such as buildings, roads, plant, etc are also reflected in the physical model. The dam break problem is investigated for sudden partial collapse which is simulated by a trapezoidal breach on the dam body. The water depths are measured by using e+ WATER L (level) sensors. The velocities are determined by Ultrasonic Velocity Profiler (UVP) transducers. The propagation of the flood is recorded by a HD camera. The experimental results show that Urkmez area can be flooded in a matter of minutes, at depths reaching up to 3 meters in residential areas. The flood wave can reach in the residential areas in 4 minutes. Flood wave velocities at peak discharge can exceed 55 km/h

A re-evaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean

We report a new synthesis of best estimates of the inputs of fixed nitrogen to the world ocean via atmospheric deposition, and compare this to fluvial inputs and di-nitrogen fixation. We evaluate the scale of human perturbation of these fluxes. Fluvial inputs dominate inputs to the continental shelf, and we estimate about 75% of this fluvial nitrogen escapes from the shelf to the open ocean. Biological di-nitrogen fixation is the main external source of nitrogen to the open ocean, i.e. beyond the continental shelf. Atmospheric deposition is the primary mechanism by which land based nitrogen inputs, and hence human perturbations of the nitrogen cycle, reach the open ocean. We estimate that anthropogenic inputs are currently leading to an increase in overall ocean carbon sequestration of ~0.4% (equivalent to an uptake of 0.15 Pg C yr-1 and less than the Duce et al., 2008 estimate). The resulting reduction in climate change forcing from this ocean CO2 uptake is offset to a small extent by an increase in ocean N2O emissions. We identify four important feedbacks in the ocean atmosphere nitrogen system that need to be better quantified to improve our understanding of the perturbation of ocean biogeochemistry by atmospheric nitrogen inputs. These feedbacks are recycling of (1) ammonia and (2) organic nitrogen from the ocean to the atmosphere and back, (3) the suppression of nitrogen fixation by increased nitrogen concentrations in surface waters from atmospheric deposition, and (4) increased loss of nitrogen from the ocean by denitrification due to increased productivity stimulated by atmospheric inputs

Data for: Effect of the sediment discharge on the equilibrium bed morphology of movable bed open-channel confluences

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Distorted Physical Model to Study Sudden Partial Dam Break Flows in an Urban Area

WOS: 000344005700006A distorted physical model, based on Urkmez Dam in Izmir, Turkey, was built to study sudden partial dam break flows. The distorted model had a horizontal scale of 1/150 and a vertical scale of 1/30, containing dam reservoir, dam body, and downstream area-from dam body to Urkmez urban area until the sea coast. In the model, the reservoir is approximately 12 m(3), the dam body has a width of 2.84 m and a height of 1.07 m, and the downstream area is nearly 200 m(2). The Urkmez Dam was chosen because Urkmez Town is located right at its downstream area, allowing the study of dam break flows in an urban area. Furthermore, the dimensions were suitable such that it allowed the construction of a physical model (dam reservoir, dam body, and downstream area) having a horizontal scale of 1/150 in the available space of 300 m(2). The features creating roughness such as buildings, bridge, and roads were also reflected in the physical model. The dam break flow was investigated for sudden partial collapse, which was simulated by a trapezoidal breach on the dam body. The water depths at downstream area were measured at eight different locations by using e+ WATER L (level) sensors. The velocities were measured at four different locations by ultrasonic velocity profiler (UVP) transducers. The propagation of the flood was recorded by a high-defnition camera. The experimental results show that the Urkmez area can be flooded in a matter of minutes, at depths reaching up to 3 m in residential areas in 4 min. The flood wave front can reach the residential areas in 2 min and to the sea coast in 4 min. Flow velocities can reach 70.9 km/h in sparse residential areas, close to dam body. Away from the dam body in the sparse buildings part of the town, the velocities can reach 27.7 km/h. In dense residential areas of the town, the velocities are too low (2.8 km/h) but flow depths can reach 3 m. Velocity profiles show similar behavior like unsteady and nonuniform open channel flow in nonresidential areas close to the dam body. In residential areas away from the dam body, the velocity profiles are more uniform, having lower velocity values. Vertical variations of velocities show markedly different behavior during rising and recession stages. The profiles are smooth during the rising stage in sparse residential area, yet it shows fluctuating behavior during the recession stage. (C) 2014 American Society of Civil Engineers.Turkish Science and Technological Research Council (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110M240]This study is financially supported by Turkish Science and Technological Research Council (TUBITAK) through the 110M240 project. We deeply thank TUBITAK. Our gratitude goes to Izmir Municipality and IZSU Administration for their contributions on the acquisition of the required drawings and the relevant maps. The writers would also like to thank Professor Dr. Turhan Acatay for his valuable advice

Experimental investigation of time-dependent clear water scour around bridge pier due to a trapezoidal hydrograph

Environ. Water Resour. Inst. (EWRI) Am. Soc. Civ. Eng.World Environmental and Water Resources Congress 2012: Crossing Boundaries -- 20 May 2012 through 24 May 2012 -- Albuquerque, NM -- 92565Local scours around bridge piers influence their stabilities and play a key role in bridge failures. In this study, the local scours around a bridge pier resulting from unsteady flow are investigated. The experiments are carried out in a rectangular flume 80 cm wide and 18.6 m long by using uniform sediment with median diameter of 3.5 mm and geometric standard deviation of 1.4. The unsteady flow is generated by means of a trapezoidal hydrograph. The bridge pier with circular cross section has a diameter of 8 cm. The flow depth is monitored by ultrasonic sensors and the flow rate is measured by electromagnetic flow meter. The temporal variations of scour depth are measured indirectly, by placing Ultrasonic Velocity Profiler (UVP) transducers downward vertically. Three transducers of 4 MHz are located around the bridge pier. The local scours due to input hydrograph are obtained by registering the distances from the tip of the transducer to the top level of the sediment layer in the course of unsteady flow experiments. The temporal evolution of local scours as well as the final depths and configurations of the local scours are obtained. The experimental findings are interpreted in the light of present classical knowledge. This study constitutes the first part of the researches planned to investigate the time dependent local scours due to various trapezoidal hydrographs. Keywords: trapezoidal hydrograph, bridge pier, local scour, UVP, temporal evolution © ASCE 2012

Experimental investigation of time-dependent clear water scour around bridge pier due to a trapezoidal hydrograph

Local scours around bridge piers influence their stabilities and play a key role in bridge failures. In this study, the local scours around a bridge pier resulting from unsteady flow are investigated. The experiments are carried out in a rectangular flume 80 cm wide and 18.6 m long by using uniform sediment with median diameter of 3.5 mm and geometric standard deviation of 1.4. The unsteady flow is generated by means of a trapezoidal hydrograph. The bridge pier with circular cross section has a diameter of 8 cm. The flow depth is monitored by ultrasonic sensors and the flow rate is measured by electromagnetic flow meter. The temporal variations of scour depth are measured indirectly, by placing Ultrasonic Velocity Profiler (UVP) transducers downward vertically. Three transducers of 4 MHz are located around the bridge pier. The local scours due to input hydrograph are obtained by registering the distances from the tip of the transducer to the top level of the sediment layer in the course of unsteady flow experiments. The temporal evolution of local scours as well as the final depths and configurations of the local scours are obtained. The experimental findings are interpreted in the light of present classical knowledge. This study constitutes the first part of the researches planned to investigate the time dependent local scours due to various trapezoidal hydrographs. Keywords: trapezoidal hydrograph, bridge pier, local scour, UVP, temporal evolution © ASCE 2012