After five years of historic drought, Californians have come to view water as a valuable natural resource. But there is another resource they probably haven’t thought about that may be just as valuable: Mud. Or more specifically, sediment. Water makes sediment by the process of erosion, and the two are intimately connected by natural laws. We have been slow to realize that, and we’ve spent centuries trying to separate them. Dams are the most obvious example. Dams cause