CHAPTER 16 Focus Points
16.1 Stream Patterns
Drainage basins: Drainage basins are composed of tributary streams and a trunk stream. They are delineated by topographic relief.
Drainage and continental divides: Drainage divides separate different drainage basins. Continental divides separate drainage basins that empty into different oceans.
Drainage patterns: Stream tributaries form different geographic patterns. The most common pattern is dendritic drainage.
Stream order: Most streams are third-
16.2 Downcutting by Streams: Fluvial Erosion
Fluvial erosion: Fluvial erosion is the most important and widespread agent of erosion on Earth.
Stream discharge: Stream discharge is determined by climate, stream order, season, and ground permeability. High-
Stream rejuvenation: Entrenched meanders, stream terraces, and antecedent streams all result when a stream is uplifted.
16.3 Building by Streams: Fluvial Deposition
Stream sorting: Streams drop large sediments first and the lightest materials last.
Aggradation landforms: Floodplains and braided streams are formed through aggradation.
Meanders: Streams migrate across their floodplains as they form meanders and meander cutoffs.
Flooding: Streams overflow their channels and cover the floodplain with a sheet of standing water. Sediments drop out of the still water.
Delta subsidence: The input of new sediments with flooding in a delta naturally keeps pace with the natural rate of subsidence through sediment compaction. Artificial levees prevent flooding and disrupt this equilibrium.
16.4 Rising Waters: Stream Flooding
Types of flooding: Flash floods and seasonal floods are the two modes of stream flooding.
Flood mitigation: Dams, levees, and stream bypasses help reduce flooding events.
16.5 Geographic Perspectives: Dam Pros and Cons
Dam pros: Dams provide many benefits to human society, including flood control, water availability, and hydroelectricity generation.
Dam cons: Dams create many problems for people, including destruction of habitat, farmland, and human communities and beach erosion resulting from sediment starvation.