scholarly journals FIELD STUDY ON SEDIMENT TRANSPORT AROUND RIVER MOUTH OPENING AT THE TENRYU RIVER IN JAPAN

2018 ◽  
pp. 69
Author(s):  
Yuya Sasaki ◽  
Shinji Sato
Keyword(s):  
Sediment Transport ◽  
Coastal Erosion ◽  
Mouth Opening ◽  
River Mouth ◽  
Sediment Supply ◽  
Optimal Management ◽  
Central Japan ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Near Future

The Tenryu River mouth and its surrounding coast, located on the Pacific Ocean side in the central Japan, have been suffered from severe coastal erosion. Although increasing sediment supply from river to coast is planned by sand-bypassing through the upstream dams in near future, a better understanding on morphology change around river mouth is needed to facilitate optimal management of the river mouth. Especially, understanding on sediment transport around the river mouth opening is essential to prevent river mouth closure which leads to many problems. The purpose of this study is to reveal the mechanism of sediment transport around river mouth opening.

scholarly journals Subseafloor basalts as fungal habitats

2012 ◽  
Vol 9 (2) ◽  
pp. 2277-2306 ◽  
Author(s):  
M. Ivarsson
Keyword(s):  
Morphological Characteristics ◽  
Microbial Life ◽  
Ocean Drilling ◽  
Potential Habitat ◽  
The Pacific ◽  
Fungal Hyphae ◽  
The Pacific Ocean ◽  
Life On Earth ◽  
Near Future ◽  
Deep Subseafloor

Abstract. The oceanic crust is believed to host the largest potential habitat for microbial life on Earth, yet, next to nothing is known about this deep, concealed biosphere. Here fossilised fungal colonies in subseafloor basalts are reported from three different seamounts in the Pacific Ocean. The fungal colonies consist of various characteristic structures interpreted as fungal hyphae, fruit bodies and spores. The fungal hyphae are well preserved with morphological characteristics such as hyphal walls, septa, thallic conidiogenesis, and hyphal tips with hyphal vesicles within. The fruit bodies consist of large (~50–200 μm in diameter) body-like structures with a defined outer membrane and an interior filled with calcite. The fruit bodies have at some stage been emptied of their contents of spores and filled by carbonate forming fluids. A few fruit bodies not filled by calcite and with spores still within support this interpretation. Spore-like structures (ranging from a few μm:s to ∼20 μm in diameter) are also observed outside of the fruit bodies and in some cases concentrated to openings in the membrane of the fruit bodies. The hyphae, fruit bodies and spores are all closely associated with a crust lining the vein walls that probably represent a mineralized biofilm. The results support a fungal presence in deep subseafloor basalts and indicate that such habitats were vital between ∼81 and 48 Ma, and probably still is. It is suggested that near future ocean drilling programs prioritize sampling of live species to better understand this concealed biosphere.

scholarly journals Sand Bypassing Methodology For Sustainable River Mouth Opening

2019 ◽  
Vol 8 (2S11) ◽  
pp. 2280-2284
Keyword(s):  
Sediment Transport ◽  
Tamil Nadu ◽  
Mouth Opening ◽  
River Mouth ◽  
The Other ◽  
Natural Sediment ◽  
Water Level Rise ◽  
Model Study ◽  
River Training ◽  
The Impact

River inlets along the Tamil Nadu coast remain mostly closed due to negligible fresh water flow and also due to various structures constructed near to the river inlet obstructing natural sediment transport. Excessive development of the sand spit also causes serious problems such as water level rise during floods and difficulty in navigation through river mouth. To reduce the impact of coastal area flooding and easy navigation it is necessary to keep the river mouth open. River training walls (RTW) are generally constructed to keep the river mouth open. Depending upon the sediment transport direction, sediments get deposited on one side of the RTW, while depleting the sediments from the other side. To prevent the sediment deposit from spilling over to river mouth, it is ideal to bypass the sand to the other side of the river mouth. This study analyses the methodologies for sand bypassing. A numerical model study has been carried out using DHI LITPACK to evaluate the sedimentation. The procedure of sand bypassing using pumps and pipe lines are discussed. Volume of sand bypassed, pump capacity, the number of Booster pumps to maintain critical velocity etc. can be determined based on the procedure discussed

scholarly journals World’s largest dam removal reverses coastal erosion

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jonathan A. Warrick ◽  
Andrew W. Stevens ◽  
Ian M. Miller ◽  
Shawn R. Harrison ◽  
Andrew C. Ritchie ◽  
...  
Keyword(s):  
Coastal Erosion ◽  
Large Scale ◽  
River Mouth ◽  
Dam Removal ◽  
Ocean Waves ◽  
Sediment Supply ◽  
Sediment Budgets ◽  
Self Organized ◽  
Wave Angle ◽  
Mouth Bars

Abstract Coastal erosion outpaces land generation along many of the world’s deltas and a significant percentage of shorelines, and human-caused alterations to coastal sediment budgets can be important drivers of this erosion. For sediment-starved and erosion-prone coasts, large-scale enhancement of sediment supply may be an important, but poorly understood, management option. Here we provide new topographic measurements that show patterns and trends of beach accretion following the restoration of sediment supply from a massive dam removal project. River sediment was initially deposited in intertidal-to-subtidal deltaic lobes, and this sediment was reworked by ocean waves into subaerial river mouth bars over time scales of several months. These river mouth bars welded to the shoreline and then initiated waves of sediment accretion along adjacent upcoast and downcoast beaches. Although the downcoast shoreline has a high wave-angle setting, the sedimentation waves straightened the downcoast shoreline rather than forming self-organized quasi-periodic instabilities, which suggests that simple coastal evolution theory did not hold under these conditions. Combined with other mega-nourishment projects, these findings provide new understanding of littoral responses to the restoration of sediment supplies.

scholarly journals CHANGES DUE TO JETTIES AT TILLAMOOK BAY, OREGON

1976 ◽  
Vol 1 (15) ◽  
pp. 103 ◽  
Author(s):  
Paul D. Komar ◽  
Thomas A. Terich
Keyword(s):  
Coastal Erosion ◽  
New South ◽  
Littoral Drift ◽  
Erosion And Deposition ◽  
Oregon Coast ◽  
The North ◽  
The Pacific ◽  
Tillamook Bay ◽  
Severe Erosion ◽  
The Pacific Ocean

Bayocean Spit, separating Tillamook Bay from the Pacific Ocean on the north Oregon coast, underwent severe erosion following construction of a north jetty at the bay entrance in 1914-17. This erosion ultimately led to the complete breaching of the spit in 1952. Simultaneous to the spit erosion south of the entrance, the shoreline north of the north jetty advanced seaward by some 600 m (2000 ft). This pattern of erosion and deposition following jetty construction has generally been interpreted as the jetty blocking a large north to south net littoral drift in the area, estimated by a previous study at 620,000 m3/yr (800,000 yd3/yr). Our reexamination of the shoreline changes and patterns of erosion and deposition following jetty construction disagrees with this interpretation, and instead we conclude that all of the changes resulted from local rearrangements of the beach due to the disrupted equilibrium following jetty construction, but at the same time maintaining an overall condition of zero net littoral drift. This interpretation is supported by other evidence that indicates a near-zero net drift on this portion of the Oregon coast. Thus severe coastal erosion can result from jetty construction even in areas of zero net littoral drift. A new south jetty has been recently completed (1974). The result has been further realignments of the shoreline with accretion and shore-: line advance immediately south of the south jetty. This provides further confirmation that a zero net littoral drift exists in the area. This study also demonstrates the effects of building only a single jetty rather than a pair of jetties. Following construction of the north jetty, the outer bar or ebb-tide delta at the Tillamook Bay inlet grew appreciably in size.

scholarly journals Prediction of Shoreline Change for the Calculation of the Integrated Littoral Sediment Budget

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 232
Author(s):  
Yeon-Joong Kim ◽  
Jong-Sung Yoon
Keyword(s):  
Sediment Transport ◽  
Coastal Erosion ◽  
Evaluation System ◽  
Shoreline Change ◽  
Sediment Budget ◽  
Prediction Performance ◽  
Sediment Supply ◽  
Sediment Runoff ◽  
Observation Data ◽  
Sediment Volume

The severe coastal erosions are being accelerated along the east coast of South Korea owing to the intermittent erosions and depositions caused by the imbalance between the effective sediment volume supplied from coasts and rivers and the sediment transport rate. Consequently, many studies are being conducted to develop coastal-erosion reduction measures. To accurately determine the cause of coastal erosion, the causes of the erosion and deposition should be accurately diagnosed, and a comprehensive evaluation system for the sediment transport mechanism in the watershed and sea while considering regional characteristics is required. In particular, realizing the evaluation of the effective sediment volume that flows from the river to the sea through observations is a highly challenging task, and various research and developments are required to realize it, as it is still in the basic research stage. The purpose of this study was to systematically analyze the comprehensive sediment budget for coastal areas. First, an analytical system was developed. Then, a shoreline model was constructed by considering the size of the mixed particles. The parameters required for developing the model were determined using the observation data to improve the shoreline model. A sediment runoff model was applied to evaluate the effective sediment volume supplied from the river to the sea, and the applicability of this model was evaluated by comparing it with the sediment supply volume according to the soil and water assessment tool model. The representative wave and the input parameters of the model were set using the observation data of several years. It was found that the prediction performance of the shoreline change model improved when the effective sediment volume was considered, and the particles of the sediment on the shore were assumed to comprise multiple sizes. In particular, the prediction performance improved when the balance of the sediment budget was adjusted by applying a groin having a structurally similar performance to take into consideration the geographic features of the Deokbongsan (island) in front of the river mouth bar. The model demonstrated a good performance in reproducing long-term shoreline changes when the characteristics of the sea waves and the effective sediment volume were considered.

Larval Konosirus punctatus(Clupeidae) in a brackish river mouth on the Pacific coast of central Japan

2006 ◽  
Vol 68 (5) ◽  
pp. 1362-1375 ◽  
Author(s):  
M. Kawasaki ◽  
Y. Watanabe ◽  
N. Shirafuji ◽  
M. Chimura ◽  
M. Moku ◽  
...  
Keyword(s):  
Pacific Coast ◽  
River Mouth ◽  
Central Japan ◽  
The Pacific ◽  
Konosirus Punctatus

Postglacial environmental change of the Pacific Ocean off the coasts of central Japan

1987 ◽  
Vol 11 (4) ◽  
pp. 273-291 ◽  
Author(s):  
Kiyotaka Chinzei ◽  
Kantaro Fujioka ◽  
Hiroshi Kitazato ◽  
Itaru Koizumi ◽  
Tadamichi Oba ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Environmental Change ◽  
Central Japan ◽  
The Pacific ◽  
The Pacific Ocean

scholarly journals Microplastics Pollution in Chile: Current Situation and Future Prospects

2021 ◽  
Vol 9 ◽  
Author(s):  
Esteban Paredes-Osses ◽  
Karla Pozo ◽  
Andrés Opazo-Capurro ◽  
Paulina Bahamonde ◽  
Jaime R. Cabrera-Pardo
Keyword(s):  
Microbial Communities ◽  
Environmental Policies ◽  
Future Research ◽  
Future Prospects ◽  
Research Directions ◽  
Industrial Activities ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Future Research Directions ◽  
Near Future

Millions of tons of plastics enter wild habitats, especially the oceans, every year. Despite extensive efforts, this amount is predicted to increase over in the near future, leading to a catastrophic damage to the environment. Small plastic fragments, including microplastics, are currently widely distributed in different environments and contribute significantly to pollution of the oceans. This problem is particularly poignant in Chile, a country with more than 4,000 km of coastline along the Pacific Ocean home to diverse environments, industrial activities and unique biodiversity. In this review, we compile information regarding microplastics pollution in Chilean environments in terms of transport, distribution and bioaccumulation along the country, societal actions such as environmental policies and education to tackle the plastic problem, and the Trojan effect associated with it. Finally, we identify critical scientific gaps, such as the transport of harmful chemicals and microbial communities associated, and define potential future research directions.

scholarly journals Long shore sediment transport computation for Hai Hau beach-Nam Dinh province

2003 ◽  
Vol 25 (1) ◽  
pp. 39-48
Author(s):  
Nguyen Manh Hung
Keyword(s):  
Sediment Transport ◽  
River Mouth ◽  
Wave Climate ◽  
Large River ◽  
Sediment Supply ◽  
Red River ◽  
Transformation Model ◽  
Wave Transformation ◽  
Random Wave ◽  
Red River Delta

Several stretches of shore line in the Red River Delta (RRD) are suffering from severe erosion, especially an area between too large river mouths Balat in the North and Day in the South, known as Hai Hau beach. Several different hypothesis have been put forward to explain this erosion. The cut off of the Ha Lan river mouth (in 1955) which discharged sediment at the upstream end of the beach, possibly affects Hai Hau beach. Also, the construction of Hoa Binh dam in the upstream part of Red river has reduced the sediment supply to the area. In this study, it is shown that the prevailing wave climate in connection with the complex topography of Balat river mouth and Hai Hau beach promotes erosion along the coastal line. A two dimensional random wave transformation model was used with 20-year time series of hindcast waves to compute the long shore sediment transport along the study beach.

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