ABSTRACT
A preliminary study on bank erosion of Sittaung River estuary in Myanmar is conducted based on satellite image analysis, field survey and numerical computation. The estuary is open with a trumpet shape to the Gulf of Martaban, and invites tidal bore with strong currents in full moon and new moon periods. Bank line retreat of 10 km in last 10 years in active zones is encountered owing to strong currents associated with the occurrence of tidal bore. Figure 1 shows bank line changes resulted from erosion these ten years. Such bank erosion and associated sediment issues are discussed with attention focused on sediment particles sizes in river reach and estuary as well as on mechanism of bank erosion owing to tidal currents. Present results are summarized as follows: (1) Sediment sizes of bed material along the reach change discontinuously at the boundary of the upper and lower reaches. Sediment composed of beds in lower reach as well as in estuary are supplied by bank erosion of river reach and estuary. (2) Bank erosion of estuary is caused mainly by strong tidal currents following the passage of a bore head. (3) Bank erosion constitutes a cyclic process such as bank collapse and associated sediment supply to the base of bank, elimination of deposited sediment and erosion of base material by tidal currents. (4) Macro-structure of tidal currents can be reproduced by means of numerical computation based on depth-averaged two-dimensional governing equations. However, fine resolutions of tidal currents are desired to discuss the relation between currents and bank erosion.
