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River flood control plays an important and essential role to prevent the loss of life and property along the riverbank. This study designed a bend flume experiment to investigate the effects of flood diversion in the middle and lower of Han River using the method of passive control. The diversion breach evolution and the relations between the diversion flow through the breach and the influencing factors were analyzed. Four stages of the entire flood diversion process of non-cohesive dikes, namely overtopping, groove formation, breach stretching and stability stages, were proposed. The research results indicated that the particle size had an obvious effect on the erosion rate during the initial flood diversion, and little influence on the maximum diversion discharge. In addition, the water head between the inside and outside of river had a significant effect on the initial flow diversion. The greater the water head, the greater the diversion discharge that occurs. Key words: middle and lower Han River, flood diversion, bend flume experiments, non-cohesive dike, diversion process. Le controle des crues joue un role important et essentiel dans la prevention de pertes de vies et de proprietes le long du rivage. La presente etude a con^u des experiences dans un canal de jaugeage courbe afin d'etudier les effets du detournement des crues dans les parties mediane et avale du fleuve Han en utilisant une technique de lutte passive. L'evolution de la breche de detournement et les relations entre le debit de detournement dans la breche et les facteurs determinants ont ete analysees. Quatre etapes ont ete proposees pour tout le processus de detournement des crues pour des digues non coherentes : le debordement, la formation de sillons, l'agrandissement de la breche et la stabilite. Les resultats de la recherche indiquent que la granulometrie avait un effet evident sur le taux d'erosion durant le detournement initial des crues, et peu d'influence sur la decharge maximale du detournement. De plus, la difference de niveau d'eau entre les parties internes et externes du fleuve avait un effet important sur le debit de detournement initial. Plus la difference de niveau d'eau etait elevee, plus le debit de detournement etait grand. [Traduit par la Redaction] Mots-cles: parties mediane et avale du fleuve Han, detournement des crues, experiences avec un canal de jaugeage courbe, digue non cohesive, processus de detournement., Introduction Flood control plays an important role in mitigating flood disasters from occurring in rivers and watersheds, particularly in inundation prevention, flood risk management, and water resource management. The diversion [...]

Landslide debris is a common occurrence in mountainous regions around the world that can potentially result in disastrous consequences to downstream facilities. Flow-impeding structures are often constructed along the flow path to impede this hazardous phenomenon. Baffles are a type of flow-impeding structure regularly installed using empirical and prescriptive design methods as the interaction mechanism and the influence of baffle configuration on flow impedance is not well understood. A series of flume experiments were carried out to investigate flows characterizing landslide debris impacting an array of baffles using dry uniform sand. The influence of baffle height, row number, and spacing between successive rows was examined. Photoconductive sensors were used to estimate flow velocity, laser sensors were installed to measure flow depth profiles, and high-speed cameras were used to capture flow kinematics. Experimental results reveal that baffles can be categorized relative to the approach flow depth (h) and increasing the baffle height from 0.75h to 1.5h leads to a 40% increase in upstream flow depths from backwater effects, more effective development of subcritical conditions, and additional energy losses of up to 9%. Increasing the number of rows of 1.5h baffles from a single row to a three-row staggered array results in up to 72% additional energy loss. The energy loss is attributed to the deflection of granular jets and additional backwater effects. Increasing the row spacing from 50 to 100 mm results in up to a 14% increase in energy loss. Key words: landslide debris, flume modelling, baffles, array configuration, flow impedance. Les debris transportes par les glissements de terrain sont souvent rencontres dans les regions montagneuses autour du globe, et entrainent des consequences potentiellement desastreuses aux installations en aval. Des structures pour empecher les ecoulements sont souvent construites le long du chemin d'ecoulement pour prevenir ce phenomene dangereux. Les deflecteurs sont un type de structure installes regulierement selon des methodes de conception empiriques et prescriptives, puisque le mecanisme d'interaction et l'influence de la configuration des deflecteurs sur la limitation de l'ecoulement n'est pas bien compris. Une serie d'essais de canaux ont ete realises pour etudier les caracteristiques d'ecoulement des debris de glissement affectes par un groupe de deflecteurs, et ce, a l'aide de sable uniforme sec. L'influence de la hauteur des deflecteurs, du nombre de rangee, et de l'espace entre les rangees successives est evaluee. Des sondes photoconductives ont ete utilisees pour estimer la vitesse de l'ecoulement, des sondes laser ont ete installees pour mesurer les profils de profondeur de l'ecoulement, et des cameras a haute vitesse ont ete utilisees pour capturer la cinetique de l'ecoulement. Les resultats experimentaux ont revele que les deflecteurs peuvent etre categorisees selon la profondeur de l'ecoulement d'approche (h), et que l'augmentation de la hauteur des deflecteurs de 0,75h jusqu'il 1,5h entraine une augmentation de 40 % de la profondeur de l'ecoulement en amont en raison des effets de retour d'eau, un developpement plus efficace des conditions subcritiques, et des pertes d'energie additionnelles jusqu'a 9 %. L'augmentation du nombre de rangees de deflecteurs de 1,5h, d'une rangee simple a trois rangees, entraine une perte d'energie additionnelle de 72 %. Les pertes d'energie sont attribuees a la deflection des jets granulaires et aux effets de retour d'eau additionnels. L'augmentation de l'espacement entre les rangees de 50 a 100 mm resulte en une augmentation de 14 % de la perte d'energie. [Traduit par la Redaction] Mots-cles: debris de glissement de terrain, modelisation par canaux, deflecteurs, configuration en serie, limitation de l'ecoulement., Introduction Landslide debris is a type of natural disaster affecting mountainous regions worldwide in Canada (Hungr et al. 2001), Italy (Arattano et al. 2012), Japan (Sassa and Wang 2005), mainland [...]

Particle saltating motions during bed load transport are dominated by the forces acting upon particles and the random process of the particles impacting on and rebounding from the channel bed. A realtime flow visualization technique is developed in this study to measure particle saltating trajectories, corresponding velocities, and impacting and rebounding angles. Based on the experimental data, regression equations for the dimensionless saltating length, height, and velocity were obtained. A numerical model that is able to simulate the continuous saltating process of a single particle was developed. The model was calibrated and verified with the experimental data, and the results were satisfactory. The model was also used to generate a series of synthetic data. Based on these data and the flume data collected by previous investigators, a bed load equation was derived.

To obtain in situ measurements of sediment erodibility in defined bottom shear stress environments, a portable, straight flume was built, tested, and deployed in the field for six experiments at three locations in Quincy Bay of Boston Harbor, Mass. The flume had a 1.0-m-long inlet section, which included a boundary-layer trip and a roughened, plexiglass bottom; this design prevented erosion of the sediment bed in the boundary-layer-development region. Downstream of the inlet section was a 1.2-m-long sediment test section, which had a laboratory-verified, uniform bottom stress. In the absence of algal mats, our flume experiments on sites exhibiting a range of bed properties indicated quite uniform erodibility, with a critical shear stress tau(sub c) of 0.10 +/- 0.04 Pa and an erosion rate constant M of 3.2 +/- 0.2 X 10(super -3) kg m(super -2) s(super -1) Pa(super -1) (R(super -2) = 0.92, N = 17, where N is the total number of erosion rate measurements made in the absence of algal mats). The measured rates were consistent with those of many other in situ studies. We observed markedly reduced erodibility in early October 1995 when the sediment was covered by a benthic diatom mat, and measured erosion rates were lessened by 50-80%. The possibility of depth-dependent sediment erodibility in near surface (top 3 mm) was investigated by calculating a set of depth-dependent erosion parameters. The parameters obtained suggested that both the critical shear stress and the erosion rate constant were depth-sensitive (both doubling by 1 mm into the sediment).

The Vedernikov number V > 1 is the necessary condition for roll-wave formation. Using the theory of linear stability, Ponce and Simons in 1977 confirmed the Vedernikov criterion for turbulent Chezy friction in hydraulically wide channels. In addition, they identified the scale of the disturbances under which roll waves are most likely to develop. Brock, in 1967, experimentally studied roll-wave propagation using a laboratory flume. Using Brock's data, an experimental verification of Ponce and Simons' theory is presented. Results show that dimensionless wave numbers corresponding to the roll waves documented by Brock's study plot near the peak of the theoretical functional relation of logarithmic decrement delta versus dimensionless wave number sigma. The analysis confirms that roll waves are most likely to form for large positive values of the logarithmic decrement (delta > 0.2), located within a narrow center band of dimensionless wave numbers. In a practical setting, this knowledge can be used to promote or inhibit the development of roll waves.

Cohesive sediment beds Occur in a variety of natural and man-made environments. A parameter that has a very significant influence on the sediment behavior is the critical shear stress. This is the shear stress at the sediment surface above which erosion will take place. The critical shear stress can be evaluated in the laboratory under conditions closely resembling those found in the field by use of an annular flume. The main purpose of the work described in this paper is to determine experimentally and numerically the velocity and surface shear stress fields generated by the flow of water in an annular flume. Very good agreement is found between measured circumferential velocity profiles, obtained by laser doppler anemometry, and profiles predicted by the computational fluid dynamics program HARWELL-FLOW3D. Measurements of the bed and wall shear stresses are made using hot-film probes and these also agree reasonably well with numerical predictions. Also of interest is the dependence of the sediment shear strength on sediment depth. By comparing measured eroded sediment contours with predicted shear stress profiles a simple method emerges for describing this dependence.

Filtration rates of infaunal bivalves were measured using a recirculating flume. The flume allows continual recirculation of water over a test section where grazers and their particle capture are localized. The filtration rates of Potamocorbula amurensis was measured on the continuous variations in phytoplankton cell density. It was shown that P. amurensis filters 100 to 580 liters (gd)(super -1) over a frees-stream velocity range of nine to 25 cms(super -1). This finding suggests the sensitivity of infaunal bivalves on flow velocity.