Abstract

• About fourty-six rivers and many streams run along the coast of Myanmar. Among them Sittaung and Bilin rivers have wetland character and enter into the Mottama Gulf. Bilin river has about 212.43 kilometers (132 miles) long. It originates from the mountainous region of the Kayin State and it flows from north to south. Since the last two decades, upstream of Bilin river has started gold mining economy (Aung Swe, 2017). Lower course of the Bilin river experiences the accelerate deposition from the headwater sources and effect of tidal action from the Mottama Gulf. Due to gradual increase of tidal range, surface saline water intrusion also gradually increased around the lower course of the Bilin river. This paper presents wetland characteristics of the Bilin riparian area by relation to the relief, climatic condition, soils and geology of the Bilin catchment area, morphological conditions of upper and lower Bilin river course, bathymetry condition of Mottama Gulf, tidal condition of Yangon river and Mawlamyine tidal gauge stations. In this research, Normalize Difference Water Index (NDWI) method used to classify deep water (active channel), shallow water and intertidal zone area. Gradually change to wetland characteristics of the lower course of the river has been identified using a time series satellite images (1990-2018) by using Geographic Information Systems (GIS) and Remote Sensing (RS) techniques. After analyzing based on the NDWI method, lower Bilin riparian area is more influenced mud flat character than the wetland character.