Abstract: Several studies on the continental Quaternary sedimentation, stratigraphy and landscape evolution of the Mahi River basin exist, however, the microbial activity including its relation with soil physical and chemical properties has not been explored. In the present investigation, estuarine and alluvial soil microbial activity (as an index of soil enzymes i.e., dehydrogenase and protease) and its relation with soil properties such as Soil Organic Matter (SOM), Soil Moisture Content (SMC), soil texture (sand, silt and clay) and soil pH has been addressed. The study was conducted at 7 sites spread over 3 locations (2 were from alluvial zone and 1 was from estuarine zone), each sampled at various depths along a 30 km long stretch of the Mahi River in western India. High microbial activity was noticed in estuarine soils than in alluvial soils. Dehydrogenase activity in both alluvial and estuarine soils indicated positive correlations with SOM, SMC and a moderate correlation with clay content. On the contrary, the protease activity showed poor correlation with SOM, SMC and clay content of alluvial soils however, significant positive correlations were noticed in estuarine soils. No correlation was observed between these two enzymes. A negative correlation existed between soil depth and both the enzymes in alluvial soils. The findings demonstrate that SOM and SMC, clay content and soil depth are the important determinants for dehydrogenase activity (indicative of organic matter transformation) in both alluvial and estuarine soils, whereas the soil depth is the lone determinant for protease in alluvial soils and its correlation with other properties in estuarine soils is site specific.