Consonant ㄷ and consonants ㅅ, ㅈ, ㅊ, ㅌ, ㅎ, ㅆ, when in the final position of a syllable, are all pronounced as [t]

낫, 낮, 낯, 낱, 낳, 났 (= 낟)

This many different orthographies are used for only one sound for the simple reason that Korean has evolved and all the different sounds have merged into one at the final position.