John Southard, in MIT's RES.12-003 (Fluid Motions, Sediment Transport, and Current-Generated Sedimentary Structures), covers how flow conditions, sediment properties, and dimensional analysis together produce bed configurations like ripples, dunes, and plane beds. Using laboratory data and conceptual models, he maps how these forms shift with flow velocity, depth, and grain size, and discusses the spectral gap separating ripple and dune scales. The lecture then turns to oscillatory and wave-generated bedforms, tracing how ripple geometry moves from two-dimensional to three-dimensional shapes under natural wave action, and to combined flows where currents and waves interact, a case Southard flags as especially hard to predict. He closes by connecting these physical bedforms to the sedimentary structures geologists find preserved in rock, framing the whole discussion as groundwork for reading ancient flow environments from the geologic record.