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In order to develop geomorphic criteria for distinguishing and locating abandoned channels and meandered belts, in this paper we examined geomorphologic characteristics from the Mun River, one of the main rivers in the Khorat Plateau, northeastern Thailand. Upstream of Mun River originated at southwestern rim of the Khorat Plateau where the river now cuts through sandstone basement. Meandering process shaped meander from upstream ending at low-lying plain about 30 km downstream from the Mun Bon Dam reservoir, and this process displays given values of geomorphic parameters including sinuosity index (SI), channel width (W) and radius of curvature (Rc). Sinuosity index was calculated to express the sinuosity of the channel. The relationship between W and Rc helps to predict channel stability and also comprehend the possibility of cutoff process. As a result, paleo- and recent flow directions of the Mun River are similar from southwest to northeast. Geomorphic parameters from eight river reaches have changed through time since 1974-2015. Two abandoned channel belts were identified, and they own an average channel width of 35 and 16 m, whereas the Mun River nowadays is of 12.7 m. SI values of two abandoned channel belts are categorized as meandering river system. Relationship between meander migration rate and bend curvature suggests that the Mun River possesses low erosion rate between 0.71 and 2.64 m/year since 1974 to the present. This rank of Rc/W ratio suggests stable state of river bank migration. Different migration indicates discontinuous meandering process from individual belt. Lateral migration rate was also decreased after Mun Bon Dam was constructed upstream. [ABSTRACT FROM AUTHOR]

The devastating December 26, 2004, tsunami produced abundant geologic effects along the Andaman coast of Thailand. The tsunami inundated the numerous sandy beaches and flowed over the adjacent aeolian dunes. On some of the dunes, the tsunami scoured circular holes 10-30 cm in diameter, and in its waning phases, it coated the holes with mud. The tsunami locally deposited a sand sheet that ranged from 0-30 cm in thickness, with an average thickness of approximately 10 cm. Sedimentary structures within the sand sheet include ripples from inflow and outflow, graded bedding, parallel lamination, and double-layered deposits. Erosion, locally severe, affected sand beaches and tidal inlets. We use these erosional and depositional features to infer the main processes that acted during inundation from the tsunami. [ABSTRACT FROM AUTHOR]