The Constructal Law predicts that flows of anything will evolve to maximize the flow through them. The principle works for all scales and mechanisms of operation. Here, we see a beach, saturated with water during high tide.
After the tide goes out, water drains through the wet sand down to the ocean.
Water flows in unseen rivulets below the smooth surface of the sand, merging and flowing into larger and more energetic flow channels. At the point where the beach drops a few inches, the flow reaches a boundary condition where the grains of sand break away from each other and start flowing with the water, breaking through the surface and forming a visible flow channel. More water spills out from tributaries along the banks and bottom of this channel, joining and adding to the more efficient flow of the narrow and fast current.
As the slope of the beach returns to its normal value, the speed of the flow slows down, In order to carry the same volume of water at a lower speed, the channel must spread out horizontally, creating a delta design using the same law of nature that creates the design of the mighty Amazon and every other river system in the world or on other worlds.
The origin of the fast flowing channels is not random. They start at relatively even intervals, revealing the unseen structure of the sub-surface tributaries that created them.
These flow dynamics work identially in every flow system in which energy is available to morph the sructure of the flow, allowing it to carry more of the flow.
For example, the roots of a tree collect water from myirad tiny root endings, merging together into the large channel of the trunk, then spreading out once again to be expired through myriad small stomata on the undersides of each leaf. This evaporation creates a pressure difference which provides the energy to draw water all the way up from the roots. The tree is a living engine which grows and onfigures itself to maximize the efficiency and volume of the water that flows through it.
From this, we can see that the patterns and designs we see in nature are not random at all, whether they are a supposedly inanimate riverbed or the architecture of living creatures or even the business, economic and social systems of human society, including the myriad of technical life forms. All of the natural world is co-evolving together in a majestic dance of life. And all animated by a simple law of nature that was hiding in plain sight waiting to be discovered by Dr. Adrian Bejan in 1996.