tFluviomarine areas are promising for development of new paddy fields if fragile soil properties, naturalwater logging and tidal behaviors receive strategic management to avoid environmental degradation.Three transects were established to investigate the complexity of sediment and tidal attributes. Soilswere sampled from each horizon of profiles and key mineralogical and chemical properties analyzed.An upper fluvial derived zone was characterized by exchangeable Ca as the dominant cation (decreasingconcentration with depth) and pyrite was absent. A lower zone derived from marine sediment was domi-nated by exchangeable Mg (increasing concentration with depth) accompanied by pyrite. The dominanceand distribution of Ca and Mg indicate the origin of sediment in tidal areas. These acid sulfate soils havelimited nutrient reserves being dominated by quartz in the sand fraction. The clay was dominated bykaolinite and illite and a variable proportion of vermiculite, resulting in variation of CEC values, beinghigh with vermiculite. Pyrite position from soil surface varied from 25 to 100 cm (mostly 50–60 cm)depending on thickness of fluvial zone and local slope morphology. Significant variations in tidal ampli-tudes led to the separation of fluviomarine areas into neap-spring tide zone (NSZ), spring tide zone (SZ)and non-flooding tide zone (NZ). Zoning allowed the selection of the SZ with low tidal amplitude andNZ as being suitable for new paddy field development. A potential drop of soil pH from 5 to 2 may occurwith serious consequences for paddy field and watercourses (huge acidity and dissolved metals at toxiclevels) if pyrite is exposed to oxidation conditions (e.g. drainage system lowering water level below pyriteposition). Water management through “controlled drainage” should be applied to avoid pyrite oxidation,soil degradation and poor water quality. This includes dimension (depth and width) of drainage canalsand maintaining water levels above the pyrite zone through control using floodgates thereby ensuringpyrite zone remains under reducing conditions