The Analyses of Seafloor Drainage System Offshore Southwest Taiwan
Date Issued
2016
Date
2016
Author(s)
Lin, Yung-Chun
Abstract
This study utilize the geographic and hydrological method of the Geographic Information System (GIS) to analyze the distribution and characters of the submarine system offshore southwest Taiwan. The study area is from 119°E to 121°E and 21°N to 23°50’N, where many submarine canyons such as Penghu, Kaoping, Fangliao and Formosa canyon have developed calculate the slope, aspect, numerical analysis on drainage, drainage density and spatial analysis on drainage pattern of seafloor topography, geomorphology theory is then applied to describe the regional characteristics and the features of the drainage related to the submarine canyons, and to discuss the relationship among the topography, structure and river developments. The bathymetry data with gird size 200×200 meters produced by the Ocean Data Bank in 2010 is used to this study. The results show that the drainage pattern of submarine canyons in the study area could be divided into 5 systems: Penghu (A), Kaoping (B), Formosa (C), Penghu East (D) and Penghu West (E). The B, D and a small part of A systems located on active margin are dominated by the parallel, lattice and rectangular drainage pattern. It is inferred that the parallel drainage pattern occurred in restricted areas on continental slope, while the lattice drainage pattern is possibly developed with the fractures or joints on seafloor. As for the rectangular drainage pattern, it could be related to the enlargement of fold or fault structures. The C, E and most parts of A system located on passive margin are dominated by the parallel and tree-like drainage pattern. We explained that submarine channels along the slope is easily developed on the steeper terrain, such as the continental slope in this area while the tree-like system pattern is mainly distributed on the flat continental shelf. The hydrological analyses reveal that the drainage density is on the average of 0.34 km-1 in A,C and E river drainage is a little higher than that in B and D river drainage (0.3 km-1). The average slope 2.8 degree at A, C and E river drainage is smoother compared to that 4.3 degree at B and D river drainage. 661 river numbers on the average for A, C and E are greater than that 556 river numbers on the average for B and D. The major aspects of A, C and E reflect the direction of canyons and sediment waves while the aspects of B and D may relate to the regions structure trend. The results of hydrological analyses show that the significant lineation or features are controlled by the steep seafloor caused from tectonics in the active margin off SW Taiwan. The topography will affect deeply the drainage pattern, the number and length of submarine channel, and the slope and aspect of topography. This study demonstrated that GIS could be successfully applied to analyze the drainage data of submarine canyon system and then to discuss the relationship between the development of the submarine anyon systems and regional structures.
Subjects
Geographic Information System
hydrological analyses
seafloor topography
submarine canyon
SDGs
Type
thesis
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