Natural drainage patterns are created where stream courses follow the lead of a landscape’s geological history and features. Characteristics of the underlying rock, steepness of slope, faults and joints in the Earth’s surface, the speciﬁc shape of particular geological formations, and the soil’s susceptibility to erosion are among the factors that affect the pattern established for the ﬂow of water in a particular place. Drainage patterns, generally rectangular to circular, might be elongated like a feather, braided at certain points like a net, or broken up by natural impoundments like lakes. They might, like the spokes of a wagon wheel, radiate from a center such as a peak, or converge toward a point, as in a closed basin. The pattern might fan out over a delta or collect myriad, many-pronged branches into a central stem. Because the shape of the pattern is determined by the land itself, it’s a useful image in analyzing and understanding the rocks and geologic structures of a particular drainage.