In a pattern sense, swales deal with pulses of energy also seen as a wave, just as sound frequency moves in waves. Their shape is a ditch and a mound and one summer in Portugal we built a swale at the beach to demostrate the technique and take advantage of the easily moved substrate for teaching purpose. This reflection, seen in a picture below, became so evident after the onlookers stopped staring intently and we sat back and enjoyed our earth scultping in the soft material. In nature now, there are pulses of energy, wave in form and disturbance in function, flowing down landscapes often causing spirals of erosion. Water runoff in rain events lifts soil particulates which has a cascading affect of negativity in watersheds below and farm fields above. Hence the Permaculturists attitude that swales are so great as they can help to reinforce the pattern of the overbeck jet- growth and return, true regeneration. They infiltrate water that normally would runoff thus supporting perennial vegetation and a flourishing soil food web which helps to rebound bio-diveristy in general.
via Permaculture Swales | A Permaculture Design Course Handbook.