Abstract
This study focuses on the large sand waves in the Taiwan Banks. Our goals are to observe the sand waves as completely as possible, to obtain their direction, wavelength, density, and ridge length, to analyze their spatial distributions, and to understand the effects of the current field and water depth on the sand waves. This study demonstrates the possibility of using HJ-1A/1B sun glitter imagery with a large swath width and rapid coverage in studying sand waves. Six cloud-free HJ-1A/1B optical images with sun glitter signals received during 2009 to 2011 were processed. The sand waves were mapped based on their features in the images; their direction, wavelength, density, and ridge length were measured and analyzed. We identified 4604 sand waves distributed in an area of 16,400 km2. The distributions of sand waves and their characteristics were analyzed, and the differences of sand waves between the northwestern subregion and the southeastern subregion are reported. Further analysis and discussion of the relationships between spatial distribution of the sand waves and both the tidal current field from a numerical simulation and water depth led to some interesting conclusions. The current field determines the orientation of the sand wave, while the hydrodynamic conditions and water depth influence the shape, size, and density of sand waves to a certain degree.
Highlights
Marine sand waves are a bottom morphology widely distributed in shallow marine environments
The sand waves in the Taiwan Banks (TB) are determined and mapped using the six HJ-1A/1B images listed in Table 1, leading to the identification of a total of 4604 sand waves, which are within 117°14’ and 119°26’E, and 22°32.5’ and 23°49’N, with an east-west span of up to 228 km and a north-south span of 145 km (Fig. 5)
The spatial distribution of the sand-wave direction in the TB is illustrated in Fig. 6(a), and its histogram and probability rose diagram are shown in Figs. 6(b) and 6(c), respectively
Summary
Marine sand waves are a bottom morphology widely distributed in shallow marine environments. Their formation, migration, and spatial distribution have important influences on seabed stability, navigation safety, and pipeline engineering. A multibeam bathymetry (MB) system is currently the most effective way of determining bathymetry and is becoming the standard instrument for hydrographic survey.[1] The MB data have been widely used in various marine research projects.[2,3,4,5] the sonar (sound navigation and ranging) method is expensive in terms of manpower and material resources for conducting a complete investigation. Remote sensing has become an important and useful tool for observing and monitoring marine environments. Avoidance of the influence of sun glitter has, become an important consideration for the design and application of ocean
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