Field observation and modeling of wave set-up on a macrotidal beach: the Malipo Experiment

Choi, Jin-Yong,Park, Jun-Yong,Cho, Kyoung-Ho,Hyun, Sang-Kwon,Yoo, Jeseon,Lee, Dong-Young,Jun, Ki-Cheon BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>Korea Research Ocean & Development Institute (KORDI: now renamed the Korea Institute of Ocean Science & Technology, KIOST) conducted a field observation experiment (the Malipo Experiment) using a variety of wave gages and current meters simultaneously at the Malipo Beach, South Korea, from December 2009 to March 2010 in order to understand the coastal processes in a macrotidal environment. The Malipo Beach has a typical macrotidal beach environment characterized by a very gentle beach slope of 1/50 and strong tidal currents corresponding to the extreme tidal range of 7 m. As a part of this program, we observed the intertidal-zone wave set-up using a wave-rider buoy moored at 20 m water depth and seven pressure-type wave gages perpendicularly aligned to the shore at the intertidal zone for 17 days beginning from December 17th, 2009 in order to understand wave breaking and set-up characteristics in the macrotidal environment. Based on the observation data analysis, the relationship between the wave set-up and wave height at offshore (H-s,H-0) is eta= 0.11H(s,0) showing that influence of alongshore tidal currents on the wave set-up was negligible. It was analyzed that, however, wave set-up might be influenced by shore-normal currents. The wave set-up at the study site was smaller than previous researches. It might result from its low breaking index and the wave characteristics of short wave period and wide-spreading directional spectra at the study site. Results of model simulation by combining a wave model with a circulation model showed that simulated wave set-up heights were generally lower than the measurements.</P>

Estimation of storm surge inundation and hazard mapping for the southern coast of Korea

Yoon, Jong-Joo,Shim, Jae-Seol BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>The coastal area of Korea is damaged by the approach of typhoons every year. The most serious inundation damage, with loss of lives and properties, was caused by typhoon Maemi in September 2003. After this event, there has been increased interest in addressing these coastal zone problems. It is therefore desirable to accurately forecast the storm surge height. In this study, using a numerical finite-volume coastal ocean model (FVCOM), a storm surge was simulated to investigate its inundation characteristics for the coastal area at Masan, Yeosu and Busan cities on the southern coast of Korea. In the model, a moving boundary condition (wet-dry treatment) was applied to examine inundation propagation by storm surge. The model grids were extended up through the lowland area by applying the DEM, made by precisely combining the airborne-LiDAR survey and bathymetry data. A minimum 30 m resolution unstructured triangular mesh was applied to calculate the storm surge and inland inundation. Simulated inundation range and depth were compared with the inundation map made from field measurements after the typhoon event. The results of inundation simulations in this study show good correspondence with not only the observed inundation area but also inundation depth. We also estimated the special inundation level distributions for each return period. The numerical model system adopted in this study could be a useful tool for analyzing storm surges, and for predicting coastal inundation. In addition, it is necessary for preparing detailed evacuation plans, including hazard maps for associated storm surge inundation problems.</P>

Outlier detection and missing data filling methods for coastal water temperature data

Cho, Hong Yeon,Oh, Ji Hee,Kim, Kyeong Ok,Shim, Jae Seol BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>Outlier detection and missing data filling (imputation) processes are essential first step in the statistical analysis of coastal monitoring data. Here, we suggest methods for completing these key processes. An outlier detection method that uses approximate and detailed components is suggested. The decomposition of the time-series data is performed by harmonic analysis. Next, the modified z-score method is applied to the residuals (detailed component) to detect outliers. After removing the outliers in the residuals, the filling process for the missing and removed outlier data is conducted by summing the random and the approximate components. Among the environmental monitoring data, this method is applied to the coastal water temperature data. We used hourly interval coastal water temperature data provided by the NFRDI (National Fisheries Research & Development Institute). In these datasets, the dataset of the Yeong-Deok Geomuyeok (36.58 degrees N, 129.40 degrees E) station, Korea, is only used for this method application. This dataset contains some outliers and missing data. To test the model performance, this method is applied to a daily interval modeling dataset from the HYCOM (Hybrid Coordinate Ocean Model). This method provides reasonable results for outlier detection and for filling in missing data in coastal water temperature datasets.</P>

Evaluation of Sub-aerial Topographic Surveying Techniques Using Total Station and RTK-GPS for Applications in Macrotidal Sand Beach Environment

Lee, Jeong-Min,Park, Jun-Yong,Choi, Jin-Yong BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>Accurate documentation of monitoring beach topographic changes is an essential component of coastal process research and management. Thanks to rapid development of technology, accuracy and quality of recent beach land surveying data have improved accordingly. As increasing demand for detailed beach topography, the adoption of a proper survey design and data collection strategy is also a crucial factor in order to collect high-density data accurately and efficiently within a given time. Especially, an efficient topographic surveying technique, by which the required time and manpower for a survey can be minimized, should be considered in the case of macro-tidal beach environment having a limited daytime for surveying the exposed intertidal zone. As a part of the Coastal Erosion Monitoring And Prediction (CEMAP) system development program of the Korea Institute of Ocean Science and Technology (KIOST), we conducted accuracy and efficiency tests for four different beach-profile surveying methods of: 1) spot measurement using a total station; 2) spot measurement using a RTK-GPS system; 3) continuous walking measurement using a RTK-GPS backpack system; and 4) continuous measurement using a RTK-GPS system mounted on an all-terrain vehicle (RTK-GPS ATV system) at the Gosapo macro-tidal sand beach, South Korea. Test results indicate that the RTK-GPS spot measurement method have the lowest vertical error of about 2 cm, which includes equipment and operation errors, while the rest of them have similar vertical errors with a range of 3 - 6 cm. In terms of survey efficiency, the RTK-GPS ATV system have advantages in surveying time and operational manpower with a reasonable vertical error of about 3 cm over the other surveying methods. As a result, The RTK-GPS ATV system is the most suitable surveying method for examining the beach volume and morphologic changes in a macrotidal sand beach, while the spot measurement methods using the total station or the RTK-GPS system are adequate for accurate beach-profile change analysis.</P>

Preliminary 3D Assessment of Coastal Erosion by Data Integration between Airborne LiDAR and DGPS Field Observations

Song, Dong-Seob,Kim, In-Ho,Lee, Hyung-Seok BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>The airborne Light Detection And Ranging (LiDAR) system has been allowed in monitoring various natural hazards, so highly accurate and airborne LiDAR data have been used in the field of oceanic sciences, including a digital terrain modeling and bathymetric mapping. In this study, we adopted airborne LiDAR measurements to assess coastal erosion for the first time. The airborne LiDAR data were acquired along the east coastal zone of Korea (shoreline is about 205km). The 3D topographical data and digital orthophotos, which were obtained from aerial LiDAR with a digital camera, were integrated with the beach profiles conducted by the VRS-based DGPS surveying. The integrated dataset were relocated into a developed flight simulator module, which is a Dynamic geographical information system solution with Digital AirScape (D-DAS), for the 3D visual analysis of erosion status. The 3D visual result of seasonal and yearly variability with respect to beach width is validated to understand the evolution trends of the coastal environment on the test areas. Preliminary result from this study shows the potential availability of LiDAR data and the additional opportunities within the 3 dimensional monitoring of coastal evolution, for a detailed evaluation of erosion supported by the Coastal Erosion Monitoring Program (CEMP). Additionally, we expect that the early introduction of the airborne LiDAR Bathymetry (ALB) system in Korea, such as Scanning Hydrographic Operational Airborne Lidar Survey (SHOALS), will be used for more effective and deliberative monitoring of coastal erosion in the coastal zone management program.</P>

Adverse Effect of Planting pine on coastal dunes, Korea

Choi, Kwang Hee,Kim, Yoonmi,Jung, Pil Mo BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>Forestation on the coastal dunes has been regarded as one of the best programs that help to stabilize the dune landscapes and protect the residential area from strong winds, blown sands, and salt spray. Introducing exotic species for dune stabilization was very common in the past. However, it could deprive coastal land of its ability to naturally recover, causing a retreat of coastline as well. As a typhoon passed through the Korean Peninsula early September in 2010, coastal dunes along the west coast of the peninsula were severely damaged during the storm. Some dunes retreated landward more after erosion, while others recovered their original profile through aeolian transport processes mainly in winter season. Vegetated dunes with pine trees recovered relatively less after the erosion than grass-covered dunes. Planting pine trees may interfere in these interactions, weakening natural recuperative power. We compared the characteristics of wind environment, morphology, and vegetation between the grass-covered dunes and the dunes covered with pine trees, for the purpose of the effectiveness of planting trees on dunes. The pine forest decreases the wind velocity on the front side of the dune to less than 50% of the grass-covered dune. Especially, the velocity of the strong winds faster than 4.5 m/s diminished to 25% of the control sites, resulting in decreased blown sand supply. Flora is also changed in the forested area. Terrestrial plants have invaded after pines were planted. In contrast, natural flora gets disappeared after the introduction of alien and exotic species. This study suggests that planting tree is likely to lead negative impact on coastal dunes. It may result in a retreat of coastline, loss of land, and devastation of dune ecosystems.</P>

Variability of Residual Currents and Waves in Haeundae Using Long-term Observed AWAC Data

Lim, Hak Soo,Kim, Chang S.,Lee, Hee Jun,Shim, Jae Seol,Kim, Seon Jeong,Park, Kwang Soon,Chun, Insik BioOne (Coastal Education and Research Foundation) 2014 JOURNAL OF COASTAL RESEARCH Vol.72 No.special

<P>The Haeundae in the southeastern Korean Peninsula is a famous beach which is one of the most popular tourist attractions of Korea in summer. It is about 1.6 km long and 40 m wide facing the southeastern sea of Korea and Korea Strait. During strong winds in winter and severe typhoons in summer, the beach is significantly eroded by waves and nearshore currents in the surf zone. Thin intensive coastal developments during last 30 years have caused substantial beach erosion and bathymetric changes in the nearshore area, despite various beach restoration projects, including beach nourishments. Recently, the government decided to construct two submerged breakwaters near both ends of the beach to enhance the preservation potential of the beach replenishments. We estimated the seasonal variations in residual currents from one-year flow measurements using the Acoustic Wave and Current (AWAC) meter, at two locations of Haeundae at approximately 15 m and 22 m in depths. Short-term flows were measured in the surf zone during summer and winter. The moving average method was applied fortnightly to estimate the residual currents. In addition, waves measured with the AWAC were analyzed to characterize seasonal variations in the beach environment of Haeundae. The observed residual currents were well matched with the simulated counterpart from a wave and current coupled model. These simulated nearshore currents appear well correlated with seasonal variations in beach erosion and accumulation. The wave and current data were also used to validate an operational coastal modeling system for the prediction of hydrodynamics. These observations will be incorporated in simulations of sediment transport in Haeundae coastal waters for developing coastal erosion control system.</P>

Comparison of Geostrophic Current Estimation around the Korean Peninsula from Remote Sensing-based MSS Models

Cho, Jaemyoung,Lee, Dongha,Lee, Miran,Cho, Jungho,Yun, Hongsik,Jeong, Taejun,Jang, Am,Kim, Taeyun BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>Altimetry satellites like Geosat, ERS-1/2, Envisat and Topex-Poseidon, which have been developed and deployed since the 1970s, have collected immense arrays of data on the sea, and the data thus gathered have been used in oceanography as well as in a variety of scientific disciplines, such as geophysics and geodesy. The mean dynamic ocean topography or Sea Surface Topography (SST), obtained by calculating the difference between the Mean Sea Surface (MSS) and the geoid surface, plays a critical role in determining the earth's shape and geoid as well as in the precision modeling of the earth's gravity field, ocean currents, and tidal waves. In the study, the MSS_CNES_CLS10 (Centre National d'Etudes Spatiales Collectre Localisation Satellites 2010) and DTU10MSS (Danmarks Tekniske Universitet 2010) MSS models calculated with the data obtained by a number of altimetry and gravity observation satellites, such as Topex/Poseidon, CHAMP, and GRACE, as well as a geoid model calculated from the EGM2008 gravity field model, were employed to determine the SST around the Korean Peninsula and to calculate its geostrophic current, the key source of the sea surface current. The SST and geostrophic current were also calculated using the MSS_CNES_CLS10 and DTU10MSS MSS model calculated from the satellite data, as well as a geoid model calculated from the EGM2008 earth's gravity field model, with a maximum degree and order 20 In the study, comparing calculated velocity with measured data and previous researches, calculated velocity of current is as 2 to 4 times faster than measured velocity at the East Sea which changes depth rapidly. However, it is similar to velocity and direction at over 40km far from the coastal area and the Yellow Sea which changes depth gradually. Also, as a result of comparison with two MSS models, MSS_CNES _CLS10 model is more accurate than DTU10MSS model, but the difference was trivial. If it is possible to estimate the movement of oceanic current which are affected by wind, pressure, density, tides and temperature of ocean, and add onto method of estimating geostrophic current used in this research, we will be able to estimate in more detail at the oceanic current This study would provide some useful data for maritime voyage and fishery.</P>

High-Resolution Operational Coastal Modeling System for the Prediction of Hydrodynamics in Korea Using a Wave-Current Coupled Model

Lim, Hak-Soo,Chun, Insik,Kim, Chang Shik,Park, Kwang Soon,Shim, Jae Seol,Yoon, Jong Joo BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>We have developed a high-resolution operational coastal modeling system for the coastal waters of Korea using a wave-current coupled model ROMS. The operational oceanographic system consists of operational modeling and monitoring modules. The modeling system comprises atmospheric and hydrodynamic models coupled with three-dimensional hydrodynamics, wave, sediment transport, and water quality model. The hydrodynamic variables are forecasted on a 72-hour basis. The real-time monitoring system is comprised of buoy, HF-radar and geostationary Communication Ocean Meteorological Satellite (COMS). The web-GIS-based coastal information system provides predicted results with real-time monitoring data for dissemination to the public and validation of the predicted results. The operational coastal modeling system uses the ROMS hydrodynamic model coupled with SWAN, a wave model. WRF is used for meteorological modeling of atmospheric forcing, NAO.99jb is a regional tide model used for the tides, and CE-QUAL-ICM is an eutrophication model that is used for simulating the water quality. The atmospheric forcing is derived from the predicted results of the WRF atmospheric model, which has been operated for forecasting in the East China Sea and East Sea. The ocean boundary condition is derived from data-assimilative ROMS, which has been in operation for the Yellow Sea. The hydrodynamic variables were calibrated with tidal surface elevation and verified with current data observed by a bottom-mounted ADCP and AWAC. To validate the predicted results, we use real-time monitoring data from hydrodynamic measurements observed by the operational AWAC and buoy, 1-h averaged surface currents measured by HF-radar, and suspended sediment concentration (SSC) obtained hourly and derived from the Geostationary Ocean Color Imager (GOCI) of COMS. The wave-current coupled ROMS-SWAN modeling system shows enhanced wave-current interaction for the coastal waters of Korea, especially for the prediction of storm surge height and variation of suspended sediment transport. This operational coastal modeling system has been originally developed for the prediction system of coastal waters of Korea and used for the development of an Integrated-Maritime Prediction System (I-MAPS) supporting the operation of the major ports system of Korea such as Incheon and Gunsan on the western coast of Korea, and Yeosu, Masan and Busan on the southern coast of Korea. I-MAPS will also provide monitoring and predicted data to governmental agencies and to the public to support ship navigation and marine activity and to solve problems associated with coastal accidents, such as storm surge, inundation, search and rescue, and oil-spills, as a part of the Korea Operational Oceanographic System (KOOS) which will be in operation by the end of 2013.</P>

Application of GOCI Satellite Data to Ocean Modeling

Kim, Chang S.,Park, Young-Je,Park, Kwang Soon,Shim, Jae Seol,Lim, Hak-Soo BioOne (Coastal Education and Research Foundation) 2013 JOURNAL OF COASTAL RESEARCH Vol.65 No.-

<P>This study demonstrates possible application of satellite data to numerical modeling, and vice versa, to improve the quality of the processed information. A new geostationary satellite with the three missions of communication, ocean and meteorology was launched in June 2010. The ocean mission part, GOCI (The geostationary Ocean Color Imager), is now in data service of ocean color images at every hour during daytime with a spatial resolution of 500 m. The scanned data covers the north Pacific with focusing on Korean Peninsula and adjacent seas. Using the optical sensors, the GOCI images usually contain the cloud-blocked zone. We investigate a method to acquire the cloud-free images of environment information by using the operational 3-D ocean model, the ROMS. The clear-image data are used as boundary condition to the numerical modeling, and then the model results are used to recover the cloud-covered area. The hourly varying image data are also excellent data for the ocean numerical modeling in terms of temporal and spatial variation of the ocean environment. By close examination of hourly producing images from GOCI, the temporal variation is very useful for operational purpose along with the three-dimensional ocean model such as ROMS. Being in operational mode, the ROMS ocean model produces temporal and structural variation of coastal features by using the compatible GOCI data, or the GOCI images can be improved by using the model results for cloud-free images. This study shows some excellent test cases on various coastal phenomena, such as a river plume of highly turbid waters, coastal upwelling, transport of algal bloom, typhoon tracking and the distribution of surface suspended sediment concentration. A method for the convergence of GOCI data and ocean model results has been introduced. The clouding network system for the convergence of satellite data and ocean model data is a promising method that combines two different media, thus yielding dynamically validated products.</P>