The coastal sediment supply of insular basins involves a dynamic process influenced by intermittent rivers and has a crucial role in shaping beaches. In the Mediterranean, many areas are semi-arid and have intermittent rivers with low sediment regimes. The nature of sediment delivery from these rivers influences coastal stability and ecosystem services. The coastal area of Coral Bay, Potamia, west Cyprus (~10 km in length) is a tourist zone facing coastal erosion issues, according to previous studies. The sediment budget depends on four small intermittent rivers that flow into this coastal zone, covering a total drainage area of ~66.0 km². Human actions impact the sediment balance; for example, the Mavrokolympos stream has been dammed upstream, trapping sediments in the reservoir. Estimating the amount of sediment transported from the watershed to rivers is vital for evaluating catchment erosion, as well as for understanding the supply dynamics to the adjacent coastal zone. This study uses the empirical method of USLE (Universal Soil Loss Equation) to estimate soil erosion from basins to rivers. Subsequently, the SDR (Sediment Delivery Ratio) module estimates river sediment supply to their outlet. Sediment yield is of particular importance because it is directly related to the quantity of sediment that is transported and accumulated on the beach. The annual soil loss for the basin is 9.23 t ha⁻¹ yr⁻¹, and the annual sediment yield deposited at the basin’s outlet is 325 t km⁻¹ yr⁻¹. The results reveal the relationship between watershed processes and coastal zones in terms of sediment transport and coastal conservation. By balancing sediment supply, we can mitigate negative impacts and promote sustainable development in coastal and riverine environments.