One of a series of platforms in a stream valley, flanking and more or less parallel to the stream channel, originally formed near the level of the stream, and representing the dissected remnants of an abandoned flood plain, stream bed, or valley floor produced during a former state of erosion or deposition. Erosional surfaces cut into bedrock and thinly mantled with stream deposits (alluvium) are designated "strath terraces. " Remnants of constructional valley floors thickly mantled with alluvium are termed alluvial terraces.