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A high-resolution or complete bathymetric map of shallow water based on sparse point measurements (depth soundings) is often needed. One possible approach to such maps is passive remote sensing of water depth by using multispectral imagery in the popular method proposed by Lyzenga et al. [2006]; however, its application has been limited due to insufficient accuracy. To improve accuracy, we have developed 3 extensions of Lyzenga's method by addressing unrealistic optical and statistical assumptions in the method. The purpose of this paper is to compare the accuracy of Lyzenga's method, the 3 extensions, and the combination of the 3 extensions. The accuracy comparison test was performed for 2 coral reef sites by using cross validation.

The results indicated that for both sites, the extended methods were more accurate than Lyzenga's method when sufficient training data were available. The most accurate extension was the one derived by modeling the spatial autocorrelation in the error term of the regression model used in Lyzenga's method. The combination of the 3 extensions was even more accurate than the extensions.

The implementations of the extended methods are not difficult in terms of software availability and computational cost.

A hypothetical continuous rigid frame bridge was used to study the dynamic characteristics of deep-water bridges. The dynamic characteristics of the bridge under anhydrous conditions were first calculated. The fluid-solid interaction between piers and water was then simulated and finite element models under different water depth condition were established. The dynamic characteristics analysis for the hydrous condition was then carried out and compared with that of the anhydrous condition. The results show that an increase in water depth has a significant impact on the bridge's dynamic characteristics. The natural frequencies are lower than that of anhydrous condition. As the water depth increase, the natural frequencies of the structure decrease faster and the higher order frequencies decrease more dramatically. The first order natural frequency decrease approximately 5% and some higher frequencies decrease 27% when the water depth is 50m. Therefore during the design stage, the impact of water depth on the dynamic characteristics of the bridge should be taken into account, especially for the deep-water bridges.

Storm surge is influenced by many factors including environmental and geographical conditions. However, laboratory experiments and filed measurements were not easy to carry due to danger and difficulties. In this study, we conducted a numerical study with a verified storm surge model. Storm surge was impacted by track, tide, water depth and sea level rise. The track of storm is related to size of storm and the range of impact could be estimated by their relationship. One of the characteristics on storm surge is that storm surge is strongly affected by water depth and surface elevation. We found that variation of storm surge could be different at each tide and depth and it makes a big difference in the western sea of Korean Peninsula whose averaged depth is about 40 m and tidal range is about 10 m. An increasing sea level rise by climate change can cause a little reduction of storm surge by its own characteristics.