scholarly journals CHANGES OP SEA BED DUE TO DETACHED BEEAKWATEES

1976 ◽  
Vol 1 (15) ◽  
pp. 91 ◽  
Author(s):  
Osamu Toyoshima
Keyword(s):  
Flood Control ◽  
Sandy Beaches ◽  
Sediment Supply ◽  
Beach Erosion ◽  
Sea Bed ◽  
Open Sea ◽  
New Type ◽  
Japanese Islands ◽  
Coastal Land ◽  
Sea Cliffs

Since most of the coast lines of Japanese Islands are faced on the open sea and are always attacked by severe waves, beach erosion is one of serious problems in the coastal engineering field. Although Japan has all types of coastal land-forms except the glacial shoreline, remarkable recessions of coast line have been observed at sea cliffs and sandy beaches. The recession of sea cliffs has been found at several districts in Japan since old times. But, beach erosion has become increasingly severe since the early 1950's. The main causes of beach erosion are the reduction in sediment supply from rivers and the interception of the longshore paths of sediment. The former is caused by the river improvement works and by the construction of dams and debris barriers or Sabo works. The later is caused by the coastal structures, such as jetties, groins, breakwaters, and flood-control outlets. In addition a new type of beach erosion has been observed at the coast where coast protection works such as seawalls and bulkheads exist. The beach erosion defence works are being executed at more than 300 sites in Japan. Considerable number of the works were commenced in the 1960's.

scholarly journals MARINE SEDIMENT CHARACTERISTICS AT KARIMUN JAVA SEA BASED ON STRATIGRAPHIC PROFILE ANALYSIS, TOTAL SUSPENDED SOLID (TSS) AND GRAIN-SIZE ANALYSIS (GRANULOMETRY)

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Suryantini Suryantini ◽  
Aris Ismanto ◽  
Indarta Kuncoro Aji ◽  
Dwi Fajar Saputri ◽  
Helfinalis Helfinalis
Keyword(s):  
Grain Size ◽  
Sea Water ◽  
Total Suspended Solid ◽  
Suspended Solid ◽  
Sediment Supply ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Research Activities ◽  
Sea Bed ◽  
Java Sea

A sedimentology survey was conducted during “Pelayaran Kebangsaan” research activities with a marine vessel of "Baruna Jaya VIII" in Karimun Java Sea. The objectives of the research were to determine the characteristics of marine water and its sediment, which are important control for coral reef growth in the study area. The survey acquired samples of Total Suspended Sediment (TSS) and gravity coring. Several analyses were then carried out on those samples; TSS analysis to determine the amount of suspended sediments in sea water that reflect the water quality for marine ecology, stratigraphic profile and sediment thickness pattern analyses to determine the sources of sediment, and grain-size analysis based on granulometry to determine deposition energy and grain-size distribution in the area. Those analyses were both conducted on-board Baruna Jaya VIII research vessel and P2O LIPI laboratory in Jakarta. The results showed that in Java Sea nearby Karimun Java Islands, the sediment supply came from the surrounding islands. Two sedimentary units were found in this area. The first units has thickness of tens centimeter from sea bed surface. It is characterized by grayish green color, grain size variation from clay to coarse sand, soft or low density and abundance with shells. The second unit is located beneath the first one, indicated by sharp contact. It is characterized by brownish color, higher density resembling the density of rock, less compacted and can be broken easily by hand, with occasionally thin carbon lenses or remnant of decomposed vegetation, and less shell or fossil At sea surface, TSS distribution shows value between 0.018 and 0.034 gr/l, with average of 0.025 gr/l, whereas at near bottom sea, it ranges between 0.024 and 0.030 gr/l, with average value of 0.027 gr/l. The granulometry shows that more than 50% of sediment is characterized by the abundance of grain size greater than 3 phi. It suggest that sea water around Karimun Java Islands was clear and the current was relatively calm. These conditions were relatively stable for a long time span. Those sea characteristics were important for successful growth of coral reefs and its complementary marine biotas. However, further studies and researches based on chemical and physical characteristics of sea water, and plankton and microbiology variation and abundances are necessary to confirm those presuppositions.Keywords: total suspended solid, gravity coring, stratigraphic profile, granulometry, Karimun Java Sea

scholarly journals NEW TYPE BLOCKS FOR SEAWALL SLOPE PROTECTION

1984 ◽  
Vol 1 (19) ◽  
pp. 170 ◽  
Author(s):  
Osamu Toyoshima
Keyword(s):  
Coastal Areas ◽  
Beach Erosion ◽  
Shore Protection ◽  
Land Preservation ◽  
New Type

Japan is a mountaineous country, and coastal areas have been looked upon quite valuable. In most cases, shorelines were slightly advancing until 1950, although there are some exceptional coasts which have been under continuous erosion for more than a thousand years. However, in the last thirty years, beaches began to be eroded one after another, and the countermeasure against beach erosion has become one of the most important problems in the national land preservation. Since the early 1960's, many seawalls against the beach erosion have been constructed. The table shows the amounts of the shore protection works constructed in the last twenty years.

Recovery Assessment of Two Nearby Sandy Beaches with Contrasting Anthropogenic and Sediment Supply Settings

2016 ◽  
Vol 75 (sp1) ◽  
pp. 462-466 ◽  
Author(s):  
Nadia Senechal ◽  
Jonathan Pavon ◽  
Remy Asselot ◽  
Mohammed Taaouati ◽  
Sophie Ferreira ◽  
...  
Keyword(s):  
Sandy Beaches ◽  
Sediment Supply ◽  
Recovery Assessment

scholarly journals Relating Hydrodynamic Forcing and Topographic Response for Tide-Dominated Sandy Beaches

2020 ◽  
Vol 8 (3) ◽  
pp. 151 ◽  
Author(s):  
Evelien Brand ◽  
Anne-Lise Montreuil ◽  
Rik Houthuys ◽  
Margaret Chen
Keyword(s):  
Intertidal Zone ◽  
Spring Tide ◽  
Field Measurements ◽  
Sandy Beaches ◽  
Tidal Currents ◽  
Sediment Supply ◽  
Wave Steepness ◽  
Natural Sediment ◽  
Order Of Magnitude ◽  
Study Sites

To relate hydrodynamic forcing and topographic response for a tide-dominated sandy beach, extensive field measurements were carried out in the intertidal zone. Hydrodynamics and beach topography were monitored during a total of 12 weeks at two different study sites: one with a featureless intertidal zone and one with intertidal bars. The results of both study sites indicate that the intertidal beach grows when wave steepness is small, whereas it erodes when wave steepness is large. Spring-neap variations in tidal current direction heavily distort this trend: strong spring tidal currents transport sediment away from the beach, resulting in enhanced erosion. Tide-induced beach volume changes are on the same order of magnitude as wave-induced changes. Besides waves and tides, the effect of variations in the amount of sediment supply is substantial, with enhanced accretion when the sediment supply is large. The effect of variations in sediment supply on the intertidal beach topography is subordinate to the effect of waves and tide, though. From this study, it is concluded that larger waves are primarily erosive, but they can also enhance the natural sediment supply. Furthermore, it is found that tidal currents can be equally important as waves in shaping the beach topography, especially during spring tide on macrotidal beaches.

Flood Disaster in Japan

2007 ◽  
Vol 2 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Kazuya Inoue ◽  
Keyword(s):  
Social Factors ◽  
Urban Areas ◽  
Flood Control ◽  
Control Policy ◽  
Material Damage ◽  
Urban Flood ◽  
Flood Disasters ◽  
Development Accounting ◽  
New Type ◽  
Area Development

Progress against flood disasters since the end of Word War II has shown that although human casualties have sharply decreased, material damage has not, despite improvements in flood control facilities. This is partly due to the increased concentration of buildings, infrastructures, and other assets in urban areas. Both natural and social factors are listed, and the implementation of suitable flood control policies is indispensable to saving lives and mitigating disasters in the future. Urban flood disasters are focused as a new type disaster explained in detail, stressing a combination of structural and non-structural measures and wide-area development accounting for both rivers and their entire basins to distribute the load in terms of flood control policy.

scholarly journals Are saltflats suitable supplementary nesting habitats for Malaysian Plovers Charadrius peronii threatened by beach habitat loss in Thailand?

2007 ◽  
Vol 17 (3) ◽  
pp. 211-223 ◽  
Author(s):  
Maï Yasué ◽  
Allison Patterson ◽  
Philip Dearden
Keyword(s):  
Hatching Success ◽  
Low Cost ◽  
Sandy Beaches ◽  
Beach Erosion ◽  
Breeding Habitat ◽  
Success Rates ◽  
Large Area ◽  
Air Temperatures ◽  
Aquaculture Ponds ◽  
Resort Development

AbstractResort development and coastal beach erosion have led to declines in beach breeding habitat for the near-threatened Malaysian Plover (Charadrius peronii) in the Gulf of Thailand. Semi-natural saltflats may provide supplementary nesting areas. We compared the environmental conditions, incubation behaviour and nesting success of plovers breeding on sandy beaches and saltflats in Thailand. In total we monitored 21 and nine nesting attempts in 2004 (beaches and saltflats, respectively) and 26 and 22 nesting attempts in 2005. Despite higher air temperatures in the saltflats (P < 0.0001), we detected no significant differences in nest attendance (P = 0.542 and P = 0.885 for 2004 and 2005, respectively), number of incubator changes between parents (P = 0.776 and P = 0.823) or number of parental nest departures (P = 0.087 and P = 0.712) during 120 incubation observations on 55 nests. There was also no difference in hatching success between beaches in 2004 (beach = 0.65, saltflat = 0.55; P = 0.692, n = 26) and 2005 (beach = 0.46, saltflat = 0.35; P = 0.539, n = 41). These results suggest that saltflats may provide nesting habitat for Malaysian Plovers and could help enhance overall hatching success rates by reducing nesting densities on beaches. Although there are few remaining intact saltflats in coastal Thailand, there are currently vast areas of abandoned tiger prawn aquaculture ponds that could be rehabilitated into saltflats at relatively low cost. Given the large area of disused aquaculture ponds throughout Thailand and South-East Asia and the substantial human pressure on coastal habitats, there could be considerable conservation benefits to the restoration of aquaculture ponds.

scholarly journals Beach Erosion and Consequential Impacts Due to the Presence of Harbours in Sandy Beaches in Greece and Cyprus

2015 ◽  
Vol 2 (S1) ◽  
pp. 55-71 ◽  
Author(s):  
V. K. Tsoukala ◽  
V. Katsardi ◽  
K. Ηadjibiros ◽  
C. I. Moutzouris
Keyword(s):  
Sandy Beaches ◽  
Beach Erosion

scholarly journals Assessment of island beach erosion due to sea level rise: the case of the Aegean archipelago (Eastern Mediterranean)

2017 ◽  
Vol 17 (3) ◽  
pp. 449-466 ◽  
Author(s):  
Isavela N. Monioudi ◽  
Adonis F. Velegrakis ◽  
Antonis E. Chatzipavlis ◽  
Anastasios Rigos ◽  
Theophanis Karambas ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Spatial Information ◽  
Eastern Mediterranean ◽  
Sediment Supply ◽  
Coastal Development ◽  
Beach Erosion ◽  
Coastal Protection ◽  
Intergovernmental Panel ◽  
Economic Resource

Abstract. The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean archipelago (Greece), a critical resource for both the local and national economy, and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR) under different scenarios. Spatial information and other attributes (e.g., presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the archipelago were obtained on the basis of remote-sensed images available on the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing, and SLR scenarios were estimated using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically derived estimations of wave run-up induced flooding, were then compared with the recorded maximum beach widths to provide ranges of retreat/erosion and flooding at the archipelago scale. The spatial information shows that the Aegean pocket beaches may be particularly vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths (about 59 % of the beaches have maximum widths < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection. Modeling results indeed project severe impacts under mean and episodic SLRs, which by 2100 could be devastating. For example, under MSLR of 0.5 m – representative concentration pathway (RCP) 4.5 of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) – a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29–87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily. Our results suggest a very considerable risk which will require significant effort, financial resources and policies/regulation in order to protect/maintain the critical economic resource of the Aegean archipelago.

scholarly journals A Design Method to Assess the Primary Strength of the Delta-Type VLFS

2021 ◽  
Vol 9 (9) ◽  
pp. 1026
Author(s):  
Roy Gafter ◽  
Nitai Drimer
Keyword(s):  
Critical Load ◽  
Assessment Tool ◽  
Design Method ◽  
Axial Stress ◽  
Bending Moment ◽  
Initial Assessment ◽  
Floating Structure ◽  
Open Sea ◽  
Load Effects ◽  
New Type

Very large floating structure (VLFS) is a sustainable concept centered around creating solid platforms at sea. The Delta is a new type of VLFS, designed to withstand open-sea conditions and to form, in addition to a broad deck areas, a sheltered basin of year-round operability. The design of this unique hull relies on direct calculations in order to identify critical load cases and assess their load effects. This study formulates a theoretical procedure for the initial assessment of the primary strength. The procedure analytically integrates the floatation loads while the hull rests at hydrostatic equilibrium on a wave surface and obtains the vertical and horizontal bending moment. This preliminary assessment tool enables a fast review of many load cases and provides the basic insights necessary for a reasonable initial design. Using the procedure, we conducted a primary load assessment for the design of Delta. By calculating the load response to 588 load cases, we identified the critical load scenario and the maximal axial stress. As the stress was too high, we improved the geometry in order to reduce loads and assessed proper scantlings for the critical section. We present the formulation of the procedure, the validation of the results, and the implementation for the structural design of the Delta VLFS.

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