There are several types of spillways used in dam construction based on their prominent features. The most common types include overflow spillways, which guide water smoothly over an arched crest; side channel spillways, where flow passes over a weir and into a parallel channel; open channel spillways used when there is no space for others; tunnel spillways, where flow is conveyed around the dam within an enclosed channel; and shaft spillways, with a vertical drop shaft connecting an overflow weir to a downstream tunnel. Spillways provide a safe path to release excess reservoir water and prevent dam overtopping and failure.