scholarly journals BEACH CHANGES AROUND DAWU FISHING PORT IN TAIWAN CAUSED BY OBSTRUCTION OF LONGSHORE SAND TRANSPORT AND MEASURES

2012 ◽  
Vol 1 (33) ◽  
pp. 118 ◽  
Author(s):  
Takayuki Kumada ◽  
Takaaki Uda ◽  
Jimmy J. Y. Liu
Keyword(s):  
Grain Size ◽  
Survey Data ◽  
Beach Nourishment ◽  
Contour Line ◽  
Aerial Photographs ◽  
Sand Transport ◽  
Change Model ◽  
Road Tunnel ◽  
Bathymetric Survey ◽  
Wave Overtopping

The Dawu fishing port breakwater has been extending since 1956 in Taitung City located in the southeast part of Taiwan, obstructing southward longshore sand transport. Because of the blockage of longshore sand transport at this fishing port, severe downcoast erosion occurred, resulting in the wave overtopping damage to Route No. 9 extending along the coastline, and urgent measures were required to enhance the safety of the route. As measures, beach nourishment using coarse materials including gravel produced from the construction of a road tunnel was planned, as well as the construction of groins on the downcoast. We first analyzed beach changes around this fishing port using past aerial photographs and bathymetric survey data, and beach changes were reproduced using the contour-line-change model considering changes in grain size. Then, the effect of measures was investigated using the model.

scholarly journals MOVING GRAVEL BODY METHOD TO CONTROL DOWNCOAST EROSION

2012 ◽  
Vol 1 (33) ◽  
pp. 40 ◽  
Author(s):  
Toshinori Ishikawa ◽  
Takaaki Uda ◽  
Shiho Miyahara
Keyword(s):  
Grain Size ◽  
Beach Nourishment ◽  
Contour Line ◽  
Sand Transport ◽  
Change Model ◽  
Body Method

The concept of the moving gravel body (MGB) method, in which topographic changes are controlled by beach nourishment using gravel, was introduced, using the contour-line-change model considering changes in grain size. The model was applied to the Fuji coast, assuming that coarse materials were nourished on a straight coast wherein a predominant longshore sand transport develops. The grain size that is effective for the recovery and maintenance of the shoreline and that does not cause further downcoast erosion was d, which is 5-10 times larger than that of the original sand, d0.

scholarly journals Evaluation of Effect of Beach Nourishment using Fine and Coarse Sand by Contour-line-change Model Considering Change in Grain Size

2007 ◽  
Vol 54 ◽  
pp. 641-645
Author(s):  
Takaaki UDA ◽  
Takayoshi YOSHIZOE ◽  
Yasushi MACHII ◽  
Takeshi YAMAMOTO ◽  
Kou FURUIKE ◽  
...  
Keyword(s):  
Grain Size ◽  
Beach Nourishment ◽  
Coarse Sand ◽  
Contour Line ◽  
Change Model

scholarly journals MECHANISM OF OFFSHORE SAND DISCHARGE INTO SUBMARINE CANYON TRIGGERED BY CONSTRUCTING DETACHED BREAKWATER CLOSE TO SHORELINE

2011 ◽  
Vol 1 (32) ◽  
pp. 18
Author(s):  
Koji Yamada ◽  
Takaaki Uda ◽  
Yoshio Suwa ◽  
Toshiro San-nami ◽  
Kou Furuike ◽  
...  
Keyword(s):  
Survey Data ◽  
Submarine Canyon ◽  
Sediment Supply ◽  
Beach Erosion ◽  
Aerial Photographs ◽  
Sand Transport ◽  
Submarine Canyons ◽  
Bathymetric Survey ◽  
Bed Slope

Several submarine canyons have developed offshore of the Aramata region of the Shimoni-ikawa coast in Toyama Bay, which is one of the three deep bays in Japan. The Kurobe River with a steep bed slope flows into the sea immediately north of this region, and a large amount of sediment has been supplied to this area, which has been transported by southward longshore sand transport. However, beach erosion has occurred owing to the decrease in sediment supply from the Kurobe River. Furthermore, since the construction of detached breakwaters as a measure against beach erosion, offshore sand transport has accelerated and beach erosion has become more severe. In this study, aerial photographs and bathymetric survey data were analyzed, then the mechanism of offshore sand transport was investigated using the BG model proposed by Serizawa et al. (2007).

scholarly journals Contour-Line-Change Model Considering Local Longitudinal Slope Corresponding to Grain Size Composition

2007 ◽  
Vol 54 ◽  
pp. 426-430
Author(s):  
Yasuhito NOSHI ◽  
Akio KOBAYASHI ◽  
Takaaki UDA ◽  
Takayuki KUMADA ◽  
Masumi SERIZAWA
Keyword(s):  
Grain Size ◽  
Size Composition ◽  
Contour Line ◽  
Change Model ◽  
Grain Size Composition ◽  
Longitudinal Slope

scholarly journals POSSIBILITY OF OFFSHORE DISCHARGE OF NOURISHMENT SAND IN TERMS OF SAND VOLUME AND GRAIN SIZE COMPOSITION

2018 ◽  
pp. 47
Author(s):  
Toshinori Ishikawa ◽  
Takaaki Uda ◽  
Toshiro San-nami ◽  
Jun-ichi Hosokawa ◽  
Tetsuyuki Tako
Keyword(s):  
Grain Size ◽  
Survey Data ◽  
River Mouth ◽  
Size Composition ◽  
Beach Nourishment ◽  
Fine Sediment ◽  
Sagami Bay ◽  
Grain Size Composition ◽  
Fine Material

On the Shonan coast facing Sagami Bay, part of the nourishment sand was considered to be transported offshore, devaluing the effect of beach nourishment. Beach changes after the beach nourishment were investigated using the Narrow Multi-Beam survey data, which have been collected since 2002. Analysis of the sand volume and grain size composition in the subareas showed that the effect of the beach nourishment on the deposition of fine sediment in the offshore zone was negligible, and that the fine material in the offshore zone was mainly brought from the erosion of the river mouth terrace.

COASTAL ALTERATION AND CHANGES IN SHORELINE MORPHOLOGY DUE TO ARTIFICIAL STRUCTURES IN MIIRAKU TOWN ON FUKUE IS. IN THE GOTO ARCHIPELAGO

2017 ◽  
Author(s):  
Ryo Sakamoto ◽  
Ryo Sakamoto ◽  
Satoquo Seino ◽  
Satoquo Seino ◽  
Hirokazu Suzaki ◽  
...  
Keyword(s):  
Tang Dynasty ◽  
National Park ◽  
Survey Methods ◽  
Aerial Photographs ◽  
Sand Transport ◽  
The Status ◽  
The Tang Dynasty ◽  
Coastal Changes ◽  
Century Poetry ◽  
Nagasaki Prefecture

A construction of breakwaters and other shoreline structures on part of a coast influences drift sand transport in the bay, and causes comprehensive topographic changes on the beach. This study investigated shoreline and coastal changes, taking as an example of Shiraragahama Beach in Miiraku on the northwestern end of Fukue Island, Nagasaki Prefecture (Kyushu, Japan). Miiraku, adjacent to Saikai National Park, appears in the revered 8th century poetry collection “Manyoshu” and served as a port for a ship taken by the Japanese envoy to China during the Tang Dynasty (618-709). Because of the recent development of breakwaters for a fishing harbor, the shore environments of this beach have changed significantly. In this study, the status of silt deposits and topographic changes on this beach arising from the construction of a harbor breakwater were evaluated by comparing aerial photographs taken in different years. Next, the changes in the shoreline visible from aerial photographs from 1947 to 2014 were analyzed. Lastly, the altitude of the beaches was measured using accurate survey methods. The following results were obtained: 1) coastal erosion made rock cliffs to fall off along the shore and deposited sand on this beach; 2) the more serious advances or retreats of the shoreline took place around shoreline structures; 3) sandbars and beach cliffs were formed.

Image Quality and Target Recognition

1967 ◽  
Vol 9 (1) ◽  
pp. 5-32 ◽  
Author(s):  
Corwin A. Bennett ◽  
Samuel H. Winterstein ◽  
Robert E. Kent
Keyword(s):  
Grain Size ◽  
Image Quality ◽  
Modulation Transfer Function ◽  
Target Recognition ◽  
Recognition Performance ◽  
Aerial Photographs ◽  
Modulation Transfer ◽  
Task Definition ◽  
Subject Selection ◽  
Target Characteristics

The terminology and literature in the area of image quality and target recognition are reviewed. An experiment in which subjects recognized strategic and tactical targets in aerial photographs with controlled image degradations is described. Some findings are: Recognition performance is only moderate for representative conditions. There are wide differences among target types in the recognizability. Knowledge of a target's presence (briefing) greatly aids recognition. Better resolution means better performance. Enlarging the image such that a line of resolution subtends more than three minutes of arc hinders recognition. Grain size should be kept below 20 seconds of arc. It is suggested that the eventual application of the modulation transfer function approach to measurement of image quality and target characteristics will enable a quantitative subsuming of various quality-size relationships. More attention needs to be paid in recognition research to suitable task definition, target description, and subject selection.

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