If you're wondering what this pregnant belly business is about, you have to know that mpreg (or male impregnation) is another popular trope of knotting. And while that deserves a whole post on its own (it exists both inside and outside the world of knotting and fan fiction) its connection to knotting can't be denied.
The term levocurvature of the lumbar spine means leftward deviation of the lumbar spine. The curvature is greatest (apex) at l4. Dextrocurvature or dextroscoliosis would refer to a rightward deviation of the spine. Would you like to video or text chat with me?
Also, as a river builds up its levees and raises itself over the floodplain, the slope and the transport power of the stream decrease, the channel fills gradually with sediment, and finally (often during a flood) the river will breach its levee (this process is called avulsion) and follow a steeper path down the valley.