Assesment of transportation of sediment in aquatic ecosystems originating from watersheds is essential to due to its potential role as vectors for contaminants, heavy metals, nutrients, and microplastics. In Kochi, open waste disposal at Brahmapuram has polluted the river Kadambrayar which is in close proximity to this site. An analysis of leachate collected from Brahmapuram showed presence of Arsenic, Cadmium, Chromium, Lead, Mercury, Copper, Zinc and Tin in significant concentrations (Robert et al., 2023). An analysis of river water and sediments from River Kadambrayar also showed presence of these heavy metals (Robert et al., 2023). River Kadambrayar is also reported to contain microplastics in both sediments and top soil near the waste dumping yard at Brahmapuram (Luckins et al., 2022). The study conducted confirmed the presence of an average of 100 microplastic pieces per 100 g of sediments of Kadambrayar river bordering the waste dumping yard at Brahmapuram. Accurate assessment of sediments transport from the catchment to the river will help in identifying and managing the pathway for heavy metals and microplastic transport from the top soil to the river. However, no study has been made to assess the transport of sediments in Kadmbrayar watershed. To address this gap, a numerical hydrological model was developed to simulate runoff, erosion, and sediment transport from the Kadambrayar Catchment into the Kadambrayar River using rainfall-runoff and soil erosion modeling, and sediment routing. The sediment load of 3024 tonnes of sediment for the year 2023 was obtained from the HEC-HMS software. The study conducted would serve as a tool to understand and manage the transport behavior of heavy metal and microplastics in sediments in river Kadambrayar.