The rate of windblown sand in the period with various time scales ranging between geomorphological to engineering time scales was evaluated, taking the Shonan coast extending between the mouth of the Sagami River and Enoshima as the example. The rate of windblown sand necessary for coastal management is discussed. It was estimated from the development of sand dunes after the era of Jomon transgression of sea 6000 years before present. Furthermore, taking the angle between the wind direction and the coastline into account, the rate of windblown sand at typical points was evaluated. Reviewing previous papers related to the rate of windblown sand on the Shonan coast, longshore distribution of the rate of windblown sand was proposed.

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This paper deals with the physical characteristics of three types of beach sediments, carbonate, silica and black sand, taken from natural and nourished beaches in the Philippines and Japan. Nineteen sediment samples were collected and analyzed for basic soil properties. Experimental procedures based on the American Society for Testing and Materials (ASTM, 1958) ¹⁾ standards were applied to determine grain size and coefficient of permeability where the latter was verified by a numerical analysis using Kitamura model (1998) ²⁾ . As a result, this study has confirmed that grain size is directly proportional to coefficient of permeability. In addition, the field of coastal engineering uses median grain size D₅₀ to describe beach sediment size and has been conveniently applied to estimate permeability. However, in the field of geotechnical engineering, D₁₀ proves to be technically and empirically recognized as a better index for permeability determination.

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A method for determining grain size from digital images of sediment proposed by Rubin was applied to field data and experimental data. Its accuracy is poor under sediments with the high sorting coefficient because fine-grained sand may be burned under coarse-grained sand. It is possible to estimate the grain size unless water permeates the sediment surface for the wet grained sand. But the grain size measured by digital images is nearly equal to that by sieving, The experimental data showed that the sorting process would be generated in a short period, and then fine-grained sand is deposited on the offshore side and coarse one on the onshore side under depositional wave actions.

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The relationship between the velocity distribution and the distribution of the suspended sediment concentration inside a wave around the surf zone has not been fully explained. In this study, we studied the time-space distribution of the suspended sediment concentration around the surf zone. Furthermore, we have made observations on the relationship between the velocity distribution and the distribution of the suspended sediment concentration inside a wave. As a result, it has become apparent that the distribution of the suspended sediment concentration was dependent on the flow velocity inside the wave. The suspended sediment concentration is lower during the time period before a wave reaches the breaking point. As a wave approaches the breaking point, the flow velocity at the center of the wave crest becomes greater, the bottom shear force increases, and suspended sediment concentration increases.

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Strong flow generated by bow thruster may cause a severe local scour on the seabed in front of a quay and its countermeasure is required for effective use of port facilities. This study is intended to investigate local scour and its generation mechanism by conducting hydraulic model experiments. Also, countermeasures against local scour using armor stones and filter units are investigated. In the experiments, pore pressure inside seabed is measured as well as flow velocity and bed deformations. Time variation of pore pressure indicates the generation of liquefaction due to strong flow, and this may encourage the local scour. Experimental results clearly show that armoring by filter units is effective to reduce the local scour.

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For planning and operation of shore protection facilities against beach erosion, it is necessary to understand the shoreline change trends.
Conventionally, aerial photographs are used for detection of shoreline changes. However, the major drawback of the aerial photograph is its prohibitive high cost in terms of data acquisition and processing time.
In this study, a shoreline change analysis system using satellite images from ALOS (Advanced Land Observing Satellite) has been developed. In this system, the location of shoreline is extracted as vector data from the ALOS images and previous aerial photographs.
Finally, comparison of shorelines in the vector data is carried out automatically using a GIS (Geographical Information System) system.

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A model for predicting the formation of a sandy beach on a reef flat was developed applying the contour-linechange model. The condition of a sandy beach on the Oku coast with coral reefs in Okinawa was investigated. On this beach, a stable sandy beach with a slope of 1/10 was developed due to the shoreward sand transport, the materials of which were originally supplied from the coal reef. The formative mechanism was investigated using a movable bed experiment. It was confirmed that coarse sand placed on the flat surface is carried shoreward, resulting in the formation of a beach with a steep slope. This mechanism was simulated using the BG model (Serizawa et al., 2006), given the equilibrium slope of sand. Predicted results were in good agreement with the experimental results.

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A foreshore slope changes in response to the variation of incident wave height on a coast composed of fine sand, resulting in seasonal shoreline changes. During storm wave conditions, rapid shoreline recession occurs due to offshore sand transport. Bowen (1980) showed that during storm wave conditions the equilibrium slope is reduced, since the ratio W/uof the bottom velocity of wavesuto the falling velocity of sandWtakes a smaller value under the condition that the suspended sediment load is very high. In this paper, a model for predicting these short-term changes in the foreshore slope and shoreline position in response to changes in the wave intensity was developed on the basis of the concept of equilibrium slope while applying the contour-line-change model.

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A 3-D beach deformation model considering advection-diffusion of suspended sediment has been developed to evaluate the beach topographic changes around a coastal structure. This model includes the sediment transport rate formula under the coexistence of waves and currents, considering the effect of bottom slope and undertow on the sediment transport rate. In the case of a longshore uniform beach, this model has a solution that topographic changes are affected clearly by the grain size and are influenced widespread by the coastal structures.
This model can evaluate topographic changes in terms of grain sizes, and can be available in evaluating total longshore sediment discharge including the effect of tidal and drift currents.

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Coastal erosions in sandy beaches have been serious problems for decades. In general, in order to evaluate the environmental changes in the future, beach evolution model is often used. Although the one-line model is used as a simple practical tool to predict the shoreline changes, the one-line model can not apply the beach nourishments in the offshore region. Therefore contour line change (N-line) model is needed. In this study, a numerical beach evolution model, which can predict depth contour line changes due to beach nourishment, was proposed. The effect of beach nourishment was taken into account by solving two-dimensional advection diffusion equation for nourished sand material. Some model tests of beach evolution due to nourishment were performed. Furthermore, the new N-line model was applied to preservation of eroded beach using a sand recycle method measures, and then the performance of the model was investigated.

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An artificial beach, the purpose of which is the prevention of wave didasters and the encouragement of seashore utilization, is being planned in the Takasa-Mobara area in Fukui Prefecture. When planning an artificial beach, an important issue to consider is the management of the nourishment sand which is strewn over the beach after it is built. The nourishment sand must be reviewed in terms of its grain-diameter during the designing stages of the beach so that it does not flow out into the sea under the conditions posed by the facility structure or the waves. This research sought the grain-diameter of the nourishment sand which is stable on the actual area of the sea by taking into consideration the results of a hydraulic model experiment using a plane water tank, and the value obtained from Horikawa's and Sunamura's beach section classification formula. Also, it reviewed the calmness in the artificial beach, wave height in the surrounding sea area, and the influence of the current velocity before and after the facility was serviced.

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On the Shizuoka and Shimizu coasts in Suruga Bay, many detached breakwaters have been constructed as a measure against beach erosion, originally triggered by the excessive riverbed mining in the Abe River. After the construction of the detached breakwaters, a sand accumulation zone has propagated downcoast from the river mouth with a propagation velocity of 260 m/yr as a sand body. Bathymetric surveys have been carried out yearly to monitor the movement of the sand body, and it was confirmed that the sand body is still evolving. In this study, bathymetric survey data were first analyzed, and the movement of the sand body was quantitatively predicted using the contour-linechange model. Furthermore, a method accelerating the movement of the sand body was investigated. The best way is to carry out beach nourishment with a rate of 2×10⁴m³/yr at a location 1.0km downcoast of the tip of the present sand body.

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The characteristics of the long-term shoreline changes around a delta coastline were analyzed using the contourline-change model, taking the Enshunada coast as an example. The shoreline changes between the mouth of the Magome River and Imakiri-guchi jetty were investigated, where beach changes triggered by the decrease in fluvial sand supply from the Tenryu River has been occurring. It was observed that the shoreline retreated downcoast of the mouth of the Magome River, and at the same time, shoreline advance occurred further downcoast, causing the change in curvature of the shoreline configuration. The cause of this phenomenon was well explained by the numerical model.

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Sand supply from the sea cliff to the coast was investigated, taking the Byobugaura sea cliff as an example. This sea cliff with a 10km length has been retreated for a long time while supplying sand to the Kujukuri coast with a 60 km length. This sea cliff is composed of unconsolidated layers, mostly mud stone with part of sand stone. Grain size of sand supplied from the sea cliff was investigated by the sieve analysis of the samples taken from fallen rocks, as well as the shoreline materials downcoast. The silt content is as high as 42-64% in the sea cliff, but downcoast of the sea cliff, the content of fine sand increases along the coastline, suggesting that a large amount of silt is quickly lost soon after the collapse of sea cliff.

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This paper investigates asymmetric current fields and resulting sedimentation characteristics observed around the Magome River mouth. Field survey was first conducted to obtain detailed bathymetry of the river mouth and to capture spatial current patterns by tracing wooden chips floated on the water surface. Image rectification technique was utilized to track the actual coordinates of wooden tracers. Time-varying water level and flow velocity near the bottom were also measured and, not only yielded time-varying tidal characteristics, did these data support the validity of estimated current patterns using wooden tracers. Circulation current patterns induced by broken waves were clearly observed in the area where the distance between two jetties was widened and local sedimentation was observed in the landward edge of this circulation current. This circulation current also caused asymmetric distributions of tidal current velocity across the narrow river mouth. Numerical analysis was finally conducted to investigate the influence of observed asymmetric current on the sand discharge rate at the river mouth.

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The Seisho-bypass highway runs along the Seisho coast facing the Sagami Bay. On September 6, Typhoon 0709 attacked this coast with rough waves, and the road of this highway was severely damaged over 1.1km length, resulting in full traffic stoppage. During this typhoon, maximum significant wave height reached 6m with a wave period of 14s. Damages of the road were investigated through the field observation. Strong waves attacked the coastline from the Southeast, which is in contrast to the ordinary wave direction of the Southwest. Due to this oblique wave incidence, westward longshore sand transport was developed. Along this coast, the submarine canyons develop at several locations, and part of sand transported by longshore sand transport is considered to be flowed out of the submarine canyons, causing net loss of sand.

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Short-term and long-term topographic changes of Nakatajima Dune associated with beach erosion and coastal forest development were investigated based on aerial photographs and the data of wind and regular field survey. Dynamic properties of the dune development and topographic change were obtained by the field survey showing that the edge of the dune develops 6m-8m per year although the topography of the dune keeps equilibrium. Sand transport rate was discussed by comparing topographic change with estimates by the practical formulae of wind blown sand. The formulae tend to predict smaller amount of sand transport in winter and larger amount in summer, which may be due to rainfall and vegetation.

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Beach erosion of the Shimosakurai coast located in the north part of Ibaraki Prefecture and facing the Pacific Ocean were investigated on the basis of the aerial photographs and field observation. In February 2007, extraordinary oblique waves attacked this coast, resulting in collapsing of the seawall. The direct cause of the collapsing of the structures is due to the attack of the storm waves, but the decrease in the ground level is the indirect cause which was caused by the development of the southward longshore sand transport under the condition that detached breakwaters were installed and waves were incident obliquely. The shoreline next to the detached breakwaters significantly retreated, and the seawall was severely damaged.

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Bisan-Seto Channel, which is maintained and controlled by Ministry of Land, Infrastructure, Transport and Tourism, is a very important main channel ranging from the east and west of Seto-naikai Sea. In the vicinity of the channel the sand bar shallower than 20m is extended from Mitsuko Island to the North West and sand waves on the surface of the sand bar impede safe traffic of vessels in the channel. Dredging work of about 2.2 million m3 was conducted during 1981 and 1983 as the first phase project. For decreasing sand deposits on Inosakinotsugai and maintaining the channel, the second phase dredging of 960 thousand cubic meters was carried out during 2001 and 2005 with constructing trenches at the places for sand deposits likely to be caused.
The paper discusses the influence of dredging on annual average topographic changes around Inosakinotsugai, comparing time-series volume of sand deposits between with- and without-dredging cases. The calculation of the volume with numerical simulation of tidal current is performed by means of the Multi-level Model on the basis of the regular bathymetric survey results and the in-situ observation results of tidal currents and tides during August and September 2004.

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The Immersed Tube Tunnel beneath the Bosphorus Strait is under construction in Istanbul, Turkey. When the tunnel element is immersed and set to the bottom in the trench, the sedimentation might be accelerated due to the converged current between the immersed tunnel element and the bottom. It affects the safety and the accuracy for the tunnel immersion work, significantly. In this study, the flow distributions around the tunnel element and the trench were obtained by the hydraulic physical model test at first. Then, the flow distribution and the sedimentation in the trench were calculated for the tunnel immersion work by using a numerical model. It is shown that the numerical model is capable of studying on the sedimentation for the tunnel immersion work. It is also confirmed that the immersed tunnel element is set to the bottom without the significant sedimentation in the case of the immersion work for the Bosphorus Tube Tunnel.

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Beach changes of the Nochigahama coast in Kyoto Prefecture, facing the Sea of Japan, were investigated on the basis of the aerial photographs and field observation. The Nochigahama coast is a pocket beach with a 1.1km length. This beach had been stable for a long time, but since 1964, beach erosion has become severe. The cause of the erosion was investigated. The Takeno River flows into this pocket beach, and the fluvial sand supply from this river has nourished this beach. However, since 1964, river bed mining had been carried out at the river mouth, resulting in the decrease in sand volume of this pocket beach. This became the main cause of the beach erosion on this coast.

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Beach erosion and accretion of the south Kujukuri coast was investigated based on the aerial photographs and field observation. The sand supply by northward longshore sand transport has been decreasing on this coast, causing erosion of the south part of the coast close to the sand source (sea cliff). In contrast, on the north end of the coastline, a long breakwater of the Katakai fishing port was extended and a large amount of sand has been deposited in the wave shelter zone. Furthermore, the ground subsidence up to 60cm occurred along the coastline due to the pumping-up of the ground water to obtain the water-soluble gas. The coastal situation of the south Kujukuri coast has devastated year by year due to all these impacts. To save the coast, full scale sand nourishment is required.

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Beach changes on the Narusawa, Taga and Kawarago coasts in Hitachi City in Ibaraki Prefecture were investigated on the basis of the aerial photographs and field observation. The shoreline changes between 1984 and 2006 were studied. Sea cliff extends along these coasts, and narrow sandy beaches have been formed mainly by the sand supply from small rivers. The breakwaters of Kawarago port and Ohse fishing port were constructed, resulting in the formation of the wave shelter zone. Longshore sand transport from outside to inside the wave shelter zone was induced, causing erosion outside the wave shelter zone and accretion inside it. In the eroded zone, sea cliff is exposed to waves and abrasion by gravels is underway. To protect these beaches, comprehensive management such as the sand recycling is required.

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Long-term shoreline changes of the Kita-shitaura and Miura coasts were investigated on the basis of the aerial photographs and field observations. Beach erosion has been severe on the Kita-shitaura coast, because of the recurrent dredging of the navigation channel of Kita-shitaura fishing port and the disposal. In contrast, on the Miura coast, dredged materials were placed on the shoreline, resulting in widening of the foreshore. Thus, in this area, sand balance has been lost due to the anthropogenic factors. To improve this situation, the recycling of dredged sand is required instead of constructing hard structures.

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In this research, the Ishikawa-ken area of Kaetsu coastal zone and Enshu-nada coastal zone are selected as the coastal zone where a large-scale sandy beach is left, and sedimentation control of those zones is examined in order to recover the continuity of overall movement of earth and sand, and the following plans are proposed:
1) An efficient countermeasure based on sand recycling by shipping and natural carrying system due to waves and currents in the Ishikawa-ken area of Kaetsu coastal zone.
2) An effective countermeasure based on natural carrying power due to Tenryu river flow and a sand bypass by trucking for short distance in Enshu-nada coastal zone.

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