• Journal of Environmental Science International
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• v.9 no.1
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• pp.49-55
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• 2000

An EMERGY analysis of the main energy flows driving the economy of humans and life support systems consists of environmental energies, fuels, and imports, all expresses as solar emjoules. Total EMERGY use(720.0 E20 sej/yr) of the Nakdong River Basin is 96 per cent from imported sources, fuels and goods and services. EMERGY flows from the environment such as rain and geological uplift flux accounted for only 4 percent of total EMERGY use. Consequently, the ratio of outside investment to attracting natural resources was large, like other industrialized areas. EMERGY use per person in the Nakdong River Basin indicates a moderate EMERGY standard of living, even though the indigenous resources are very poor. Population of 6.66 million people in 1996 is already in excess of carrying capacity of the basin. Carrying capacity for steady state based on its renewable sources in only 0.226 million people. EMERGY yield ratio and environment loading ratio were 1.07 and 28.52, respectively. EMERGY sustainability index, a ratio of EMERGY yield ratio to environment loading ratio, is therefore less than one, which is indicative of highly developed consumer oriented economies. This study suggests that the economic structure of the Nakdong River Basin should be transformed from the present industrial structure to the social-economic structure based on an ecological-recycling concept for the sustainable use of the Nakdong River.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.101-114
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• 2019

In this study, we carry out the numerical simulation to trace the yearly shoreline change of Mang-Bang beach, which is suffering from erosion problem. We obtain the basic equation (One Line Model for shoreline) for the numerical simulation by assuming that the amount of shoreline retreat or advance is balanced by the net influx of longshore and cross-shore sediment into the unit discretized shoreline segment. In doing so, the energy flux model for the longshore sediment transport rate is also evoked. For the case of cross sediment transport, the modified Bailard's model (1981) by Cho and Kim (2019) is utilized. At each time step of the numerical simulation, we adjust a closure depth according to pertinent wave conditions based on the Hallermeier's analytical model (1978) having its roots on the Shield's parameter. Numerical results show that from 2017.4.26 to 2017.10.15 during which swells are prevailing, a shoreline advances due to the sustained supply of cross-shore sediment. It is also shown that a shoreline temporarily retreats due to the erosion by the yearly highest waves sequentially occurring from mid-October to the end of October, and is followed by gradual recovery of shoreline as high waves subdue and swells prevail. It is worth mentioning that great yearly circulation of shoreline completes when a shoreline retreats due to the erosion by the higher waves occurring from mid-March to the end of March. The great yearly circulation of shoreline mentioned above can also be found in the measured locations of shoreline on 2017.4.5, 2017.9.7, 2017.11.7, 2018.3.14. However, numerically simulated amount of shoreline retreat or advance is more significant than the physically measured one, and it should be noted that these discrepancies become more substantial for the case of RUN II where a closure depth is sustained to be as in the most morphology models like the Genesis (Hanson and Kraus, 1989).

• Water for future
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• v.27 no.2
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• pp.73-83
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• 1994

The unproper development of the nearshore zone can enhance the diffusion of pollutant in the nearshore zone resulting in unbalanced sediment budget of beach which causes alteration of beach topography. Therefore, it is required to predict the effects of the envirnmental change quantitatively. In this paper, the depth-averaged and time-averaged energy balance equation is selected to acount for the wave transformation such as refraction, shoaling effect, the surf zone energy disipation, wave breaking index and bore, due to wave breaking in the shore region.(Numerical solutions are obtained by a finite difference method, ADI and Upwind. For the calculation of the wave-induced current, the unsteady nonlinear depth-averaged and time-averaged governing equation is derived based on the continuity and momentum equation for imcompressible fluid.) Numerical solutions are obtained by finite difference method considering influences of factors such as lateral mixing coefficient, bed shear stress, wave direction angle, wave steepness, wave period and bottom slope. The model is applied to the computation of wave transformation, wave-induced current and variation of mean water leel on a uniformly sloping beach.

• Journal of Korean Society of Forest Science
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• v.96 no.3
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• pp.300-306
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• 2007

This study was carried out to analyze the characteristics of forest environmental and stream morphological factors by using the quantification theory (I) for prediction of the suitable dam site. The results obtained from this study were summarized as follows; The selection of suitable site for erosion control dam was estimated by normalized score of each category. And the prediction method of suitable site for erosion control dam divided into class I (Very suitable site), II (Suitable site), and III (Poor suitable site) for the convenience of use. In conclusion, if we select the suitable site for construction of erosion control dam for disaster prevention, we could save the loss of tremendous budget, avoid the poor suitable site due to subjective judgment, and it would promote the functions of erosion control dam.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1445-1449
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• 2004

Even though there can be a relative long-term or short-term change of their size in natural beaches due to various changes of sea condition such as the location, weather condition (wind and rain) and sea water flow, the budget of deposits in a specific area is generally regarded to be in a condition of equilibrium in terms of technology. However, as coasts are developed by many different kinds of ways (such as construction of sea walls and estuarine, dredging for gathering the aggregate and shore protection construction for establishing a structure) and sources of silt and gravel from rivers are decreased in balanced beaches, the beaches are in a serious danger of lack of sand and sand sources which are one of the maul elements to consist of them. Many swimming beaches in East Sea are directly exposed by waves generated and transmitted from outer seas. On the other hand, the Song-Do sandy beach which is this study's target area has a great condition for beach development because it locates the deepest place that is relatively shallow in Young-Il Man and there is big energy decrease given to waves from outer seas while the waves are reaching the Song-Do beach. Nevertheless, it is considered that artificial condition changes such as dredging for site extension by POSCO, getting straight of Hyoung-San Gang river flow and extension of Po-Hang harbor caused the sand loss of the beach. Therefore, some recovery plans of Song-Do sandy beach will be presented in this study and they will be compared and examined each other by numerical modeling experiment. After that, the best plan will be recommended.

• Journal of the Korean association of regional geographers
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• v.8 no.1
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• pp.98-109
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• 2002

The long term land-cover changes and the pattern of morphological changes in foredune ridges and unvegetated dunes were investigated for about 30 years through analysing aerial photographs in Shinduri coastal dunefield, Korea. As a result, forested dune area increased while unvegetated dune area decreased continuously since 1967. Foredune ridges retreated landward about 80m away from the former coast-line in the middle part while they advanced seaward after construction of dike in the northern part during last 3 decades. Unvegetated dunes in the middle part of the dunefield were eroded at seaward side and moved landward away. These facts mean not only coastal dune area has been affected by man-made effects such as afforestation and coastal developments but also shinduri coastal dune area has been stabilized by plants and has been negative sediment budget.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.485-491
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• 2018

Because of the increase in coastal erosion problems, many studies have been conducted to prevent coastline retreat by developing low-cost, highly effective countermeasures. We developed the artificial coral reefs (ACRs) method as part of this research trend. To verify its coastal protection performance, we carried out performance tests on its wave attenuation and beach sand capture ability, which are the key barometers for this newly developed technology. In this study, three different types of methods, including natural beach, TTP, and ACRs, were used to determine the coastal protection efficiency under both ordinary and storm wave conditions. Based on the results of this study, ACRs were found to have the best wave attenuation performance and captured more than 20% of the total erosion area. This means the ACR method can be applied as a reliable countermeasure to protect a coastal zone.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.663-666
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• 2005

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately $300\times500m$ area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.228-237
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• 2015

Field observations were conducted to collect hydrodynamic and morphological data, which are needed to account for mechanisms of bathymetry changes caused by physical forcings, in Haeundae beach. In order to quantitatively describe characteristics of wave transformations and current patterns in space in winter and summer, in-situ sensors for measuring waves and current profiles were installed at three locations in the cross-shore direction and also three locations in the along-shore direction. As for the results of wave measurements, waves with main direction from the east dominate in winter while waves are incident from the S and the ESE in summer. Analysis of current data reveals that currents over the study domain are considerably influenced by a pattern of tidal motions, thereby, mainly oscillating in the direction of tidal currents, i.e., east-west directions, in both winter and summer. Currents tend to be influenced by local bathymetry in the shallow water region, with the direction changed along the depth contours and the magnitude reduced as they approach the shoreline. The results analysed from the hydrodynamic data through this study can be further combined with the morphological and bathymetry data, leading to the quantification of seasonal sediment transport rates and sand budget changes.

• Ocean and Polar Research
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• v.26 no.2
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• pp.245-253
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• 2004

The Intertropical Convergence Zone (ITCZ), where the southeast and northeast trade winds converge, is the effective climatological barrier that separates the southern and northern hemispheres in dust budget. Asian and N. American dusts dominate in fhe Pacific north of the ITCZ, while Central and S. American dust prevails south of the ITCZ. In order to understand the nature of latitudinal and depth-related variations of mineral composition in terms of relative position to the ITCZ, deep-sea core sediments were collected from $9^{\circ}N$ to $17^{\circ}N$ at a $2^{\circ}N$ interval along the $131.5^{\circ}W$ meridian and analyzed for mineral composition. The amount of illite in surface sediments decreases gradually from 65% at $17^{\circ}N\;to\;31^{\circ}N$ to 31% at 9f. In contrast, smectite increases from 11% to 56% southward. The observed mineralogical variation toward the ITCZ is attributed to the increased supply of volcaniclastic material transported via the southeast trade winds from the Central and South America source regions. Smectite-illite transition, a phenomenon that the amount of smectite increases over illite, occurs at around $10^{\circ}N$, the northern margin of the ITCZ. This result indicates that the change in latitudinal position of the ITCZ in geologic past could be recorded as a form of smectite-illite transition in deep-sea cores. The studied cores show down-core variation of mineral composition from illite-rich at the surface to smectite-rich clay suit at depths, similar to the latitudinal variation. The smectite-illite transitions observed in these cores are likely the records of changes in latitudinal position of the ITCZ. The depth and age of smectite-illite transition is getting shallower and younger toward equator, implying that the ITCZ was located farther north during late Tertiary and has shifted southward to the present position of $5^{\circ}N-10^{\circ}N$.