RUNNING WATER (RIVERS)

• Anatomy of a River System
• head or headwaters
• trunk or channel
• mouth

• 5 features that are characteristic of all rivers
• discharge - volume of water is flowing by a point in a given period of time
• velocity
• laminar vs. turbulent flow
• in addition to velocity, the depth and viscosity of the water determines whether water flow is laminar or turbulent
• laminar - shallow and smooth channel, viscous and slow moving fluid
• turbulent - deep and rough channel, less viscous and fast moving fluid

• channel configuration
• gradient - slope of stream
• shape is concave upwards (why?)
• longitudinal profile - due to...
• topography
• climate
• stream flow
• resistence of rock to erosion
• base level
• ultimate base level?
• intermediate base levels?

• load - what it carries

• Sediment Movement - dependent upon type of flow
• Erosion and transport
• erosion occurs due to:
• abrasion
• chemical and physical weathering
• undercutting

• transportation of sediment can be broken into:
• suspended load
• bed load
• competence - the size particles that a stream can move
• capacity - total volume of sediment that a stream can carry

• dissolved load

• saltation - a particle is picked up when turbulent forces are great enough, and dropped when they decrease slightly
• settling velocity - speed at which particles settle to the bottom of a channel
• Dunes and ripples - form at the bottom of a channel and represent sediments that are in transit (requirements ?)
• gentle slope faces upstream, and steep slope faces downstream

• Stream Valleys, Channels and Floodplains
• stream valleys are the entire area from the top of the slope on one side of the river to the top of the slope on the other
• usually V-shaped

• channels are the trough along the bottom of the valley that in which the stream flows
• channels can have patterns that are nearly straight to extremely circuitous
• most streams that flow across flat areas develop curves that are called meanders
• not well understood, but once they start they migrate across the floodplain due to differences in the streams flow and velocity in the channel
• velocity is greatest on the outside of the bend, this cuts into the bank on the outside bend and the river migrates in that direction
• at the same time, the slower flow around the inside of each bend allows the stream to deposit a part of its load on the point bar
• oxbow lakes are created when a meander encounters its own course and cuts itself off from the rest of the river

• floodplains are the flat area along either side of the channel onto which water overflows during a flood
• produced by the migration of the river
• during floods, the overflowing water rapidly loses energy as it escapes from the channel thereby depositing sediments on the nearby floodplain
• the greatest amount of sediment is deposited adjacent to the channel thereby creating a natural levee
• if the natural levee get too big, it can constrict and confine the rivers course

NOTE: SINCE THE FACTORS THAT CREATE RIVER FEATURES ARE DYNAMIC, RIVERS CHANGE WITH TIME.....AND DISTANCE

• examples: longitudinal profiles and recurrence intervals

• Drainage Networks
• a ridge that separates two streams serves as a divide
• divides establish drainage basins
• stream piracy
• drainage patterns show the shape and interconnection of streams and tributaries that form a particular drainage network
• types of drainage patterns
• dendritic - most popular and resembles the root system of a tree (uniform bedrock)
• rectangular- faulting controls runoff
• trellis - faulting controls runoff
• radial - mountains or hills control runoff

• Delta's
• all streams eventually empty into a large body of standing water and as the streams current dies, sediment is deposited
• as the stream becomes an obstacle to flow, the stream streams course changes and forms lobes of the delta
• the stream deposits its heaviest load near the mouth and carries the finer material out to sea