GEOG 1114 1st Edition Lecture 25 Outline of Last Lecture Weathering Weathering processes Biological Weathering Mass wasting Outline of Current Lecture The Fluvial process Stream organization Stream erosion Stream patterns Fluvial Landforms Current Lecture Introduction to Fluvial Processes Latin Fluvious meaning river Process involving running water both overland flow and stream flow Effective as an agent of erosion and deposition Contributes more to shaping landforms than all other external agents Smooth s irregularities carves sediments These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Unchanneled downslope movement of water overland flow Channeled movement of water stream flow Fluvial Landforms Stream Organization Drainage Basin or Watershed all streams are part of an organized drainage network Work can remove surface run off from a certain area Areas that drain to the valley Drainage divide Stream Order Hierarchy in order within a drainage network Smaller streams join larger ones Feed into successfully larger streams down slope Larger numbers are longer in length and watershed order Smaller drainage basins feed into larger basins Drainage patterns Each basin has a unique pattern which is related to the geology and relief of the area Dendritic tree like pattern with random merging of streams most common Trellis forms in areas of hard and soft bedrock in close contact Ride and valley province of Appalachians and Ouachita Mountains Shape modified by structure of bedrock Radial Develop around an elevated central point volcano Pikes Peak Centripetal Streams converge into a uniform basin Annular Forms in areas of hard and soft domes or basins Flow follows soft bedrock and is confined by hard bedrock Downcutting creates a v shaped valley or enriched stream Deranged develop from a disruption of a pre existing drainage pattern No coherent pattern Fault line San Andreas Fault Glaciation Canadian Shield Stream Efficiency Drainage networks evolved in a way that maximizes system efficiency so that a minimum of energy will be expended Equilibrium theory Perennial and Intermittent Streams Perennial streams are permanent in humid regions Intermittent streams arroyos wash Wadi seasonal carry water only during and immediately after a rain Valleys result when drainage basins become well established Can be broad like the Canadian or steep like the Washita River Interfluve The Shaping and Reshaping of Valleys Valley Widening as gradient decreases stream flow meanders and lateral erosion occurs Water moves fastest on outside of curves cut bank Slowest water on onside of curves accumulates alluvium Stream Energy Erosion Amounts of erosion and types of landform that develop are largely a result of Stream Energy Energy Forces Potential Energy Increases in slope increases potential energy influences stream discharge Kinetic Energy Energy of Motion of stream flow Velocity Laminar Slow Turbulent Fast Gravity Assists Flow enhances velocity Friction Nature of sides and bottom of channel Smooth faster velocity less friction Rough retards the velocity more friction Two Factors of Stream Energy Influence how much erosion and deposition will occur Stream Discharge Volume of water Carried Changes in response to PPTN Stream Velocity How fast it is moving Effected by stream gradient and friction Streams As Geomorphic Agents Stream energy affects how much erosion will take place and how much material is transported and deposited to downstream locations Erosion picking up material deepening of valleys canyon development Once channeled erosion is greatly Transport moving of sediments influenced by discharge and velocity Dissolved load fine particles dissolved in water Suspended load particles carried in suspension Bed load heavy particles rock and boulders bounced an rolled along the bottom Deposition deposition of sediments Stream Channel Patterns In response to erosion transport and deposition Straight Channels Sinuous Channels Meandering Braided Channel Fluvial Landforms Floodplains Wide low laying areas around a river River Terraces When elevation is changed due to tectonic uplift there is an increase in gradient The river is rejuvenated has more energy and begins to downcut creating a new flood plain of deposition The abandoned flood plain above the new stream channel is called a river terrace Levees Low banks that suffice to keep the stream in its channel during normal flow Bluffs or Escarpment As rivers cut deeper through sediments they can leave behind bluffs or escarpments steep slopes at the outer edge of a floodplain Alluvial Fan Fluvial Landform in Arid Regions Fan Shaped landform that develops when a high velocity streams carrying large bed loads discharges the load into a broad flat valley floor Fan shaped sediments often develop from a mountain canyon Delta Fluvial Landform in Humid Regions Similar process High velocity stream discharges its load in broad slower moving body of water Mississippi Delta