Over time, the land surface is shaped by uplift from within the earth, and the effects of water, wind, and ice. Hydrology is the science dealing with the properties, distribution, and circulation of water. A stream's physical appearance and character are the result of its adjustment to the quantity of water and extent of erosion within its watershed. A reach is a continuous section of a stream or river. The stage of a flow is the elevation of the water surface.
Stream channels contain alternating regions of riffles and pools.
During low flows, riffles are regions of shallow, rapid flow. The velocity of water in pools is lower than in the riffles. Meanders are freely-swinging, winding stream channels. Meandering stream Topography describes the shape of a portion of the earth's surface including its elevations and the position of physical and cultural features. At bankfull stage , water flow fills a stream channel to the top of its banks just to the point where water begins to overflow onto the adjacent floodplain.