Lecture 3: Bed Forms

MIT RES.12-003 Fluid Motions, Sediment Transport, and Current-Generated Sedimentary Structures, Fall 2025 Instructor: John Southard View the complete course: https://ocw.mit.edu/courses/res-12-003-fluid-motions-sediment-transport-and-current-generated-sedimentary-structures-fall-2025/ YouTube Playlist: https://www.youtube.com/playlist?list=PLUl4u3cNGP60q1Ib4pyz_FBs_lYUPr9MN Prof. John Southard builds on earlier concepts by examining how different flow conditions, sediment properties, and dimensional analysis combine to produce distinct bed configurations such as ripples, dunes, and plane beds. He uses laboratory data and conceptual models to map out how these features vary with flow velocity, depth, and grain size, highlighting patterns like the transition between flow regimes and the presence of spectral gaps between ripples and dunes. The lecture then expands to oscillatory flows and wave-generated bedforms, explaining how ripple geometry changes from two-dimensional to three-dimensional forms and how complex patterns emerge under natural wave conditions. Southard also introduces the added complexity of combined flows, where currents and waves interact, emphasizing the challenges of predicting resulting structures. The session concludes by linking these physical processes to sedimentary structures preserved in rocks, setting the stage for interpreting past flow environments from geological records. License: Creative Commons BY-NC-SA More information at https://ocw.mit.edu/terms More courses at https://ocw.mit.edu Support OCW at http://ow.ly/a1If50zVRlQ We encourage constructive comments and discussion on OCW’s YouTube and other social media channels. Personal attacks, hate speech, trolling, and inappropriate comments are not allowed and may be removed. More details at https://ocw.mit.edu/comments.