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Results of a series of experiments on local scour around spur-dike-like structures are discussed. Flow discharges are varied in the experiments and found to be positively correlated with the volumeof the scour hole and the maximum scour depth. Similarity of the growth of maximum scour depth, as well as, the shape of the scour hole is closely comparable to those in the other studies.Effectiveness of the sacrificial piles as a countermeasure to local scour is tested varying the number of piles and their position. It is observed that the position and orientation of the pile group is very important to get the lowest scour, and hence maximum protection to the spur-dike. Within the limit of the present study, it is found that at the equilibrium state, the depth of maximum scour and the scour volume are reduced by 29% and 26%, respectively, when compared to the spur-dike without sacrificial piles.

Scouring and sedimentation is one of the most important topics in costal that always has been consider for river, coastal and marine structure engineers. Using RipRap is one of the simplest and economical methods for coastal protection that is very common because it is easily available, cheap and simple for construction and low costs. Rip Rap directly and indirectly used for protection of coastal against of erosion.one of the most important topics about is provide a criteria for its design and selection that has been less studied and available investigations are in straight route while due to flow pattern in the bends scouring is sever. The purpose of this study is provide a RipRap design criteria for protection of coastal against scouring. In order to achieve the research objectives, in the laboratory conditions evaluated one riprap size of inch diameter, lengths , distances and angels. The results showed equations for design of riprap and in another part of this study evaluate present equation of other researchers for using in the bends.

It is one of the important subject in river planning works to predict flow field and bed topography in the region around spur-dikes. Especially, the qualitative understanding of the mechanism of sediment deposition produced by spur-dikes enables the effective design of spur-dike collocation. However, since various complex phenomena are coexisting in the neighborhood of spur-dikes, it is necessary to investigate which phenomenon is essential for the sediment deposition around spur-dikes. In this study, a detailed observation of flow and river bed material in an area including a spur-dike in an actual river is performed, and the mechanism of sediment deposition produced by spur-dike is discussed.

In this paper, the bed topography of a channel at a 90-degree bend was studied at the T-shaped spur dike installed at the middle of the outer bank. Numerical analyses were performed with the Sediment Simulation in Intakes with Multiblock Option (SSIIM) model. Three relative curvatures (R/B = 2, 3, and 4) related to the three sediment densities (P = 2.35, 2.5, and 2.65) were modeled in nine cases and the effects of sediment density on the bed scour patterns were studied. It was observed that the maximum amount of scour occurred near the head of the dike wing at the dike’s upstream, and the maximum amount of sedimentation occurred at the inner bank of the bend exit. By increasing the sediment density when R/B = 4, the maximum scour and sedimentation decreased to 27.41% and 46.15%, respectively. When R/B = 3, the maximum scour and sedimentation decreased to 25.93% and 23.91%, respectively. When R/B = 2, the maximum scour and sedimentation decreased to 25.98% and 10%, respectively.

In river planning, it is necessary to study the influence of river construction to the river flow and the river bed. A flow affected by the river construction is a three-dimensional complicated flow.Sand deposition and scour around the construction is caused by this complicated flow which make it difficult to grasp the river change with the construction.To investigate the mechanism of flows induced by spur-dike, we need the field survey around a spur-dike.we are reporting new results obtained from the occurrence of secondary flow behind the spur-dike.

本論文は, レーザー流速計を用いた基礎実験により, 水制背後の流れを詳細に計測し, 水制により発生する2次流の構造を初めて明らかにした. さらに, この結果を基に水制により発生する2次流のモデル化を行った. このモデルは, 水深平均流速成分に2次元モデルの流速解を用い, これを3次元運動方程式に代入することにより構造物背後に発生する2次流の算出を行うものである.

This study is concerned with the countermeasures to local scour in the downstream of river bend. The characteristic of the local flow around the river bend and the influence of spur dikes and rib-type structures on the feature of the flow is investigated through model experiments. Some usefull information of the flow affected by the river bend without countermeasures is obtained. It is shown that a spur dike set at the mid of bend section remarkably improve the conditions of main flow as well as the secondary flow; the effect of the dike depends on the set-angle. It is also indicated that the combination of a rib-type structure and a spur dike produces good results.

In numerical analyses (two-dimensional models) of flows and river-bed fluctions (variation) around spur-dikes, reproducibility is poor when the transverse shear is not accurate. To investigate the mechanism of flows induced by spur-dikes, measurement was made with laser current meters measuring two components simultaneously, and this allowed an adequate determination of the conditions of the flow around spur-dikes. The application of Plandtl's transport theory in estimating the Reynolds stress was evaluated with the experimental values. Also whether Plandtl's transport theory in estimating the Reynolds stress was evalu ated with the experimental values, and applied to the numerical analyses around structures with steady and unsteady models.

The experimental results of 3-dimensional flow field and bed evolution around spur-dike is presented. And numerical simulation method for 2-dimensional bed evolution based on 3-dimensional flow model which is considered vertical pressure distribution is proposed. This numerical model takes into account non-equilibrium sediment condition. This model is applied for the experimental results and the simulation results are in good agreement with the observed data to some extent.

Resent studies have shown that group of non-submerged spur dikes can provide a valuable habitat for fishes and macro invertebrates in addition to the function to established a more desirable river for a flood, navigation and bank erosion. The study on the effects of non-submerged spur dikes on bed deformation, water surface oscillations and mean flow characteristics by changing the spur dikes facing upstream, downstream and normal to the main flow respectively. The results showed that the spur dikes facing downstream led to the maximum scour at the tip of the dikes, the maximum one in the main channel bed. In addition, it was found that in the case with a facing downstream, resistance is largest.

One of the main parameters in design of spur dikes is the estimation of local scour depth around their tail. Spur dikes are usually built in series and their stability depends on the stability of the first spur dike. In this research, an experimental investigation is carried out in order to reduce local scouring around the first spur dike in a series of spur dikes (4 spur dikes). A smaller protective spur dike perpendicular to the flow direction is proposed to substantially reduce the local scouring. All experiments are performed in the experimental flume with moving bed. Also, all the spur dikes are rigid, and are made of pressurized plywood, straight and non-submerged. For various experimental lengths (L) and distances (X) of the protective spur dike, different value of relative velocity u / u c is calculated. Finally, in favor of statistical analysis which has been done on the experimental data, an empirical equation for the relative scouring is derived.

Spur dike which is set on movable bed is expected to create new aquatic habitats according to produce local scour and sediment deposition area. In this study, we focused on rigid bed and discussed whether spur dikes will be able to create sediment deposition area on the rigid bed. Experimental flume tests and numerical analysis were conducted to confirm the characteristics of flow, sediment transport and bed deformation around spur dikes on rigid bed. These results showed that sediment was not deposited in downstream area of spur dikes, because shear velocity is too smaller than the critical shear stress in upstream wide range of a spur dike. As a result, all bed materials were transported to the opposite bank side. Thus spur dike on rigid bed didn't promote to deposit sediment in the downstream area of a spur dike. However numerical analysis showed the possibility that unsteady flow promotes to deposit sediment in the downstream area of a spur dike, because the large transverse water surface gradient was formed in the downstream area of a spur dike during water discharge increase.

A series of experiments were conducted in which the the scour hole associated with model spur dike was measured in a 180 degree laboratory flume bend under clear-water overtopping flows. In this study, the local scour were conducted for three different shapes of oblong, rectangulat chamfered of straight spur dikes at the bend with various Froude number. The main goals of the experiments were to evaluate the effect of the three different shapes of straight spur dikes on the volume of scour and potential aquatic habitat and on minimizing erosion adjacent to the streambanks. The experiments showed that of the three different shapes of straight spur dikes tested, the least erosion of the around in the near bank region was associated with the spur dikes with oblong shape, while the greatest volume of the scour hole was associated with the rectangular shape. So it was observed that, as Froude number increases, the scour increases.

In the Ukishima region of Lake Kasumigaura, beach nourishment along with the construction of groins has been carried out to recover a sandy beach. After the beach nourishment, part of the nourishment sand was transported away from the beach, turning around the tip of the downcoast groin owing to the oblique wave incidence in winter. To enhance the stability of the beach, the groins were extended and a spur dike was constructed. To design these structures, a numerical simulation using the BG model was carried out, and the optimum shapes were determined by taking into account the seasonally changing wave direction. The effectiveness of the spur dike was numerically evaluated using the BG model.

Beach nourishment was carried out in the Ukishima region in Lake Kasumigaura to recover a sand beach. A spur dike extending in the direction of predominant waves from NW was attached to the existing groins to prevent the nourishment sand from flowing out at the downdrift end of the groin. After the beach nourishment, aerial photographs had been taken to investigate the shoreline changes and the monitoring surveys such as the bathymetric surveys and sampling of the lakebed material were carried out. It was confirmed that a dynamically stable beach was successfully formed by the construction of spur dike. Sand, the grain size of which is smaller than 0.35 mm, was transported into the zone deeper than Y.P.+0.2 m due to the sorting effect of waves.

A two-dimensional finite-element surface-water model was used to study the effects of the newly constructed U.S. Highway 82 and six newly constructed pond levees on the water-surface elevations and flow distributions in the Magby Creek flood plain east of Columbus, Lowndes County, Mississippi. Different flow scenarios within the Magby Creek flood plain were simulated using various conditions for the two floods of 1990 and the 50and 100-year floods. These various conditions include (1) the conditions for the two floods of 1990, (2) previous conditions (without the U.S. Highway 82 embankments and pond levees in place), (3) existing conditions, and (4) existing conditions with a hypothetical floodflow diversion levee at the US. Highway 82 bridge. Simulations of floodflows for the two similar floods, which occurred in 1990 after construction of the highway and pond levees, indicate that the peak discharge through the U.S. Highway 82 bridge opening was about 600 cubic feet per second, about 140 percent more than the discharge would have been without the pond levees in place. Simulations of existing conditions with the U.S. Highway 82 embankments and Magby Creek distributary bridge in place indicate that about 360 and 410 cubic feet per second would pass through the highway bridge opening to flow in the Magby Creek distributary flood plain during the peak discharges of the 50and 100-year floods, respectively. Other simulations of the 1990 floods indicate that about 600 cubic feet per second would have flowed in the distributary flood plain before construction of the highway, and about 800 and 960 cubic feet per second flowed in the distributary flood plain during the 50and 100-year floods, respectively. Simulations depicting the hypothetical floodflow diversion levee which would extend into the Magby Creek flood plain from the highway bridge opening indicate that about 950 cubic feet per second would have been diverted into the Magby Creek distributary flood plain during the 1990 floods, and about 1,500 and 1,650 cubic feet per second would be diverted into the distributary flood plain during the 50and 100-year floods, respectively. Simulations without the pond levees indicate that discharges in the Magby Creek distributary flood plain decreased by an average of about 57 percent when the U.S. Highway 82 embankments and bridge were constructed. Hows in the Magby Creek flood plain approaching Lehmberg Road increased by about 10 percent. Simulations with a hypothetical floodflow diversion levee connecting the west spur dike of the highway bridge to the east levee of pond 2 indicate that discharges in the Magby Creek distributary flood plain would increase by about 300 percent above present conditions with the highway in place. The total flows in the Magby Creek flood plain approaching Lehmberg Road would decrease by about 19 percent. Simulations indicate that the hypothetical diversion levee would increase flows in the Magby Creek distributary flood plain by an average of about 73 percent above the pre-U.S. Highway 82 conditions and decrease the pre-U.S. Highway 82 flows in the Magby Creek flood plain approaching Lehmberg Road by about 11 percent

The present status of research on erosion of sand beds around spur dikes is briefly reviewed. The experimental results of erosion of two different sizes of nearly uniform sand are presented. It is shown that a rather simple kinematic model for erosion of sand beds in a long contraction, first proposed by Straub, can be modified for application to erosion around spur dikes. The equilibrium depth of scour depends on the size of the sand and the flow depth upstream of the location of the spur dike. This is consistent with Laursen's observations around bridge piers.

The spur dike is an important building in river guiding and bank protection. In the present paper, the turbulence intensity distribution around spur dikes with different structures under the same flow condition is studied through model experiment and it gives the turbulence contours. Combining with theoretical analysis, it can be calculated that the turbulence intensity in the arc-like spur dike and fan-like are relatively weaker than that of the hook-like spur dike, and the strongest turbulence intensity occurs around the trapezoidal spur dike. The conclusion will provide a scientific basis for a reasonable choice of the structure of a spur dike, which provides the references for a better structure of a spur dike.

In this paper, flow and scour patterns resulted from the installation of two T-shaped spur dikes were evaluated in a 90° bend under clear water conditions. The submerged and non-submerged spur dikes were modeled at different locations in the bend using the numerical model. Based on the dikes’ location and submergence, different scour holes on the channel bed were formed. For all models, the maximum secondary flow power occurs at the upstream of the first spur dike and the maximum sedimentation occurs at the end of the inner bank. The maximum scour depth generally occurs at the tip of the first dike wing. The space between the spur dikes should not be more than 5 times of the dike length. In the submerged mode, the maximum scour depth decreased to 22% compared to the non-submerged mode one. Moreover, the location of sedimentation is a little further away from the bend end.

Spur dikes are used for river training purposes. To meet the navigability of rivers, the mean annual flow is considered; hence, in terms of river flooding, spur dikes are necessarily submerged. Considering the importance of submerged spur dikes, this paper studied the effects of a T-shaped spur dike’s submergence ratios on turbulent flow parameters in a 90° bend using the SSIIM as a commercial CFD model. The SSIIM numerical model solves the Navier-Stokes equations with the k- ε model on a three-dimensional, almost general, non-orthogonal grid. Submergence ratios of 0 (non-submerged), 5, 15, 25 and 50% were evaluated for parameters affecting the turbulent flow such as kinetic energy, pressure, eddy viscosity and the Froude number. It was observed that by increasing the spur dike submergence ratio from 0% (non-submerged) to 50%, in addition to changes in the values of pressure and kinetic energy, the Froude number changed in the bend and increased 2.1 times at the inner bank of the bend exit, and the eddy viscosity near the bed, which is the decisive factor of the turbulent flow, reduced by 42%. At the bed near the spur dike wing, the amount and range of kinetic energy reduced by increasing the submergence ratio. Near the bed, for all submergence ratios, the maximum pressure occurred at the upstream end of the spur dike.

Industrial contaminants and chemicals adversely impact surface water quality and may lead to serious health risks to human and ecosystems. Rivers as one of the major surface water resources receive wastewaters and transport dissolved pollutions in water through Advection-Dispersion processes. A minimum distance known as the mixing length is required for complete mixing and dispersion of the pollutants. Since the concentration of pollutants often exceeds the self-purification capacity of rivers within this distance, reducing it decreases the negative impacts on the aquatic ecosystems. Creating turbulent flows with inherent mixing characteristics is an efficient measure in decreasing the mixing length. Spur dikes that are widely used in river engineering are able to reduce the mixing length by virtue of the turbulence made in a stream. Given the fact that entry of pollutants into the surface water is inevitable and the influence of spur dikes on the characteristics of pollution transport has not been meticulously investigated, this study aimed at the numerical simulation of pollution transport in a rectangular channel adjacent to a spur dike. We thus invoked Flow-3D to simulate flow and transport characteristics around an impermeable and non-submerged rectangular spur dike. The findings of this study enhance our understanding of spur dike effects on pollution transport. Notwithstanding the fact that the spur dike effectively decreased the mixing length of the pollution, the location of the pollutant entry also played a prominent role in reducing the length of this region.