scholarly journals ON THE SCATTERING OF CONCRETE ARMOUR UNITS OF DETACHED BREAKWATERS DUE TO WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 145
Author(s):  
H. Kohno ◽  
T. Uda ◽  
Y. Yabusaki
Keyword(s):  
Beach Erosion ◽  
Aerial Photographs ◽  
Field Observations ◽  
Suruga Bay ◽  
Change Rate ◽  
Shoreline Position ◽  
The Pacific ◽  
Concrete Blocks ◽  
The Pacific Ocean ◽  
Plane Area

On the Fuji Coast 15 detached breakwaters and 17 wave dissipating breakwaters have been constructed to prevent beach erosion. By virtue of the construction of the breakwaters the retreat rate of the shoreline position has decreased. However a large number of concrete blocks have been scattered due to waves. This study investigates the actual circumstances on the scattering of the concrete armour units of the detached breakwaters through the field observations on the Fuji Coast located in Suruga Bay facing the Pacific Ocean. The change rate of the plane area of the breakwater is examined from the aerial photographs, and the relationships among the parameter, the depth at the offshore foot of the breakwater and the number of the removed concrete armour units are investigated.

scholarly journals STABILIZATION OF COAST BY CONSTRUCTION OF HEADLANDS ON THE KASHIMANADA COAST, JAPAN

1988 ◽  
Vol 1 (21) ◽  
pp. 207
Author(s):  
T. Uda ◽  
M. Sumiya ◽  
H. Sakuramoto
Keyword(s):  
Pacific Ocean ◽  
Beach Erosion ◽  
Wave Direction ◽  
Shoreline Position ◽  
Follow Up Study ◽  
Field Investigations ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Periodic Changes

Eleven artificial headlands were constructed on the OhncKashima Beach facing the Pacific Ocean to prevent further extension of beach erosion and to form the dynamically stable beach. This paper summarizes the results of the follow-up study of the new works applied on the actual coast. Field investigations such as bottom sounding around headlands and aerial photographing were conducted. It was found that the periodic changes of the shoreline configuration correpsonding to seasonal change of the wave direction exist on this coast and these variations of the shoreline position can be reduced by the effect of these headlands.

scholarly journals ANALYSIS OF BEACH EROSION AROUND LARGE-SCALE COASTAL STRUCTURES

1986 ◽  
Vol 1 (20) ◽  
pp. 171 ◽  
Author(s):  
T. Uda ◽  
M. Sumiya ◽  
Y. Kobayashi
Keyword(s):  
Large Scale ◽  
Beach Erosion ◽  
Aerial Photographs ◽  
Coastal Structures ◽  
Large Scale Structures ◽  
Spatial Changes ◽  
The Pacific ◽  
Median Diameter ◽  
The Pacific Ocean ◽  
Ibaraki Prefecture

The coast of Ibaraki Prefecture, facing the Pacific Ocean, has an alongshore stretch of 181 km. On this coast many structures associated with harbors have been constructed since early 1960s. Since then 25 years have passed, and some notable beach changes due to the influence of the construction of the coastal structures have been observed. This study aims to examine the actual situation of the beach change around large-scale structures and the damages of the coastal structures selecting the coast of Ibaraki Prefecture as the study area. For the purpose aerial photographs were taken along the coast, and the topographic surveys and measurements of median diameter of beach-face materials were made. Data of the soundings having been conducted once a year since 1975 around Oharai Port and Hazaki Fishery Harbor were collected in order to study the beach changes around the large-scale coastal structures. For the analysis of these data the comparison of the shoreline changes were performed by using four sets of aerial photographs since 1947 to the present. Moreover, temporal and spatial changes of the beach topography were investigated by the sounding data.

scholarly journals LOCAL MOVEMENTS OF SAND IN THE SURF ZONE

1986 ◽  
Vol 1 (20) ◽  
pp. 91 ◽  
Author(s):  
Kazumasa Katoh ◽  
Norio Tanaka
Keyword(s):  
Fluid Dynamics ◽  
Pacific Ocean ◽  
Surf Zone ◽  
Field Observations ◽  
Time Intervals ◽  
Injection Point ◽  
Core Samples ◽  
Fluid Velocities ◽  
The Pacific ◽  
The Pacific Ocean

The fluorescent sand tracers are injected in a point in the surf zone. Core samples are taken from the sixteen points on the circumference with the time intervals of fifteen minutes for about five hours. At the same time, the horizontal two components of fluid velocities are measured at the injection point by using an electromagnetic currentmeter. The field observations have been carried out three times on two beaches facing to the Pacific Ocean. The relations between the local sand movements and the fluid dynamics are examined on the basis of the data obtained.

scholarly journals BEACH CHANGES CAUSED BY EXTENSION OF OFFSHORE BREAKWATER AND LIMITATIONS OF ARTIFICIAL REEFS CONSTRUCTED AS A MEASURE AGAINST BEACH EROSION

2012 ◽  
Vol 1 (33) ◽  
pp. 117
Author(s):  
Yasuhito Noshi ◽  
Takaaki Uda ◽  
Yukiyoshi Hoshigami
Keyword(s):  
Pacific Ocean ◽  
Protective Effect ◽  
Beach Erosion ◽  
Contour Line ◽  
Artificial Reefs ◽  
Change Model ◽  
Fukushima Prefecture ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Sheltering Effect

Beach changes on a pocket beach of 6.5 km length bounded by Ryugu and Unoko Points facing the Pacific Ocean in Fukushima Prefecture were investigated using the contour-line-change model. The shoreline recession and excess deposition of sand in the central and southern parts of the study area, respectively, between 1980 and the 1990s were triggered by the wave-sheltering effect due to the extension of the offshore breakwater of Hirakata fishing port south of the study area. Although artificial reefs were constructed in the eroded area of the study area as a measure against beach erosion, their protective effect was limited because the wave-sheltering effect of the offshore breakwater of the fishing port is much larger than that of the artificial reefs.

scholarly journals FIELD OBSERVATIONS OF SHORELINE CHANGE BY FREQUENCY-BANDED WAVE ENERGY FLUX AND FORESHORE SHAPE

2012 ◽  
Vol 1 (33) ◽  
pp. 10 ◽  
Author(s):  
Takayuki Suzuki ◽  
Yoshiaki Kuriyama
Keyword(s):  
Wave Energy ◽  
Shoreline Change ◽  
Movement Speed ◽  
Shoreline Erosion ◽  
Field Observations ◽  
Energy Fluxes ◽  
Data Set ◽  
Change Rate ◽  
Shoreline Position ◽  
Wave Energy Flux

In this paper, correlations between shoreline change rates and six frequency-sectioned wave energy fluxes were discussed using a 5-year data set of beach profiles and offshore waves observed at the Hasaki coast. Also, an effect of foreshore beach shape on shoreline backward movement speed was discussed. From the results, it is possible to separate shoreline erosion events from shoreline advance events and shoreline stand still events by using frequency-sectioned wave energy fluxes. Furthermore, the results revealed that the shoreline position and foreshore shape affect shoreline backward movement speed. This indicates that for the estimation of the shoreline change rate, we need to consider not only wave energy but also shoreline position and foreshore shape.

scholarly journals SAND ACCUMULATION IN WAVE-SHELTER ZONE OF OHARAI PORT AND CHANGE IN GRAIN SIZE OF SEABED MATERIALS ON NEARBY COAST

2011 ◽  
Vol 1 (32) ◽  
pp. 63
Author(s):  
Takeo Matsu-ura ◽  
Takaai Uda ◽  
Takayuki Kumada ◽  
Michio Sumiya
Keyword(s):  
Fine Sand ◽  
Beach Erosion ◽  
Annual Rate ◽  
Sand Transport ◽  
The South ◽  
Bathymetric Survey ◽  
Deposition Zone ◽  
The Pacific ◽  
Sand Accumulation ◽  
The Pacific Ocean

Beach changes around Oharai Port facing the Pacific Ocean were investigated using bathymetric survey data collected over 25 years between 1979 and 2004. Between the south and offshore breakwaters of Oharai Port, 1.50×106 m3 of fine sand was deposited in this period, i.e., at an annual rate of 6.0×104 m3/yr, which was originally supplied from the Naka River 3 km north of the port. Also in the wave-shelter zone of the offshore breakwater south of the port, 7.0×106 m3 of fine sand was deposited between 1979 and 2004 at an annual rate of 2.8×105 m3/yr, which was transported by the northward longshore sand transport induced from outside to inside the wave-shelter zone of the offshore breakwater, resulting in severe beach erosion on the south coast outside the wave-shelter zone. Taking into consideration the fact that sand transport to the Kashimanada coast is now completely obstructed by the port breakwaters, sand bypassing and sand back passing to the coast from the sand deposition zone of Oharai Port are required.

Sign in / Sign up

Export Citation Format

Share Document