the flood that rushed into portland twenty years ago after nearly two months of straight rain , that hurtled up beyond the labs and damaged more than a thousand houses , swept up tires and trash bags and old , smelly shoes and floated them through the streets like prizes , that left a thin film of green mold behind , a stench of rotting and decay that did n't go away for months , began with a trickle of water , no wider than a finger , lapping up onto the docks .