What are the main types of dams based on material and structure?

Dam types include: Gravity dams - concrete mass resisting water by weight, triangular cross-section. Arch dams - curved concrete, transfer load to abutments, suitable for narrow valleys. Buttress dams - concrete face supported by buttresses, economical for wide valleys. Embankment dams - earth or rockfill with impervious core or facing, most common worldwide. Selection depends on valley topography, foundation conditions, material availability, and purpose (storage, diversion, flood control).