Dam-systems are critical for water security and flood protection in arid region watersheds, yet their performance is often compromised by rapid reservoir sedimentation. Traditional planning often prioritizes individual site capac ity, neglecting the cascading sediment fluxes through the dam-system within drainage networks of the watershed. This study presents a comprehensive modeling and optimization framework for sediment-informed dam-system planning. The methodology integrates the WaTEM/SEDEM model, which quantifies spatially distributed erosion and sediment delivery to the drainage network, with StoDyM+ (Storage Dynamics Model Plus), a directed-network model simulating cascading sediment routing through the dam-system. This approach quantifies annual variations in reservoir sediment trapping, remaining storage, and dam lifespans. To solve this high-dimensional problem-characterized by the simultaneous optimization of spatial locations and storage capacities across five competing objectives of system longevity, sediment retention capacity, and functional resilience-the framework utilizes a multi-objective optimization approach powered by the advanced evolutionary algorithm, NSGA-III. Applied to the Wadi Baysh watershed (7076 km2), Saudi Arabia, using the same number of dams and cumula tive storage as the existing system, results demonstrate that a connectivity-based redistribution of locations and storage configurations substantially improves dam-system performance. The optimized configuration achieved a mean dam lifespan of 77 years, compared to 47 years for the existing infrastructure, showing improved siltation resilience by better balancing sediment inflows to the reservoirs with their respective storage volumes. The frame work provides a scalable decision-support tool for cost-effective planning and sustainable water infrastructure management in data-scarce, erosion-prone arid watersheds.