Fluvial Systems GPH 111

What are Fluvial Processes?  Collection of surface water into organized sequence of channelized forms whereby sediment is transported from the continents to ocean basins.

Fluvial Processes within Geomorphology Sierra Estrella Mountains and the Gila River

Fluvial Deposition Fluvial Deposition - Mountains weather and erode, rivers then transport the debris to the sea. Delta The Amazon River Delta Brazil, South America

The Longitudinal Profile! Maintains an “Equilibrium Gradient” Rivers only want the energy to transport their water and supplied sediment to ocean basins, and nothing more!

Key Concepts! Discharge - Amount of water flowing in a river Slope– The inclination of the river channel Sediment Load – Sediment transported Vegetation – Along and within the channel Rivers only want the energy to transport their water and supplied sediment to ocean basins, and nothing more!

How do rivers adjust over time? Similar to an airline that tries to fill all seats for their flights, no MORE or LESS. Equilibrium Happy Company! Equilibrium - Just enough fuel to carry planes full of passengers to their destinations and nothing more – Happy Company! Too Full! not enough Too Full! – Upset passengers, not enough fuel or flights to transport customers Too Empty! too too Too Empty! – Upset passengers, too much fuel or too many flights to transport customers.

How do rivers adjust over time?

Channel Aggradation Massive sediment input leads to extreme aggradation. teepens channel to increase available energy “Steepens channel to increase available energy”

Channel Incision  Commonly takes place through knickpoint retreat!! Let’s go outside!!! Lowers available energy “Lowers available energy”

Channel Incision

Channel Widening and Narrowing  The role of width to depth ratios in fluvial energy  Higher width to depth ratios the more energy loss to friction  The role of width to depth ratios in fluvial energy  Higher width to depth ratios the more energy loss to friction

Channel Widening Increase width to depth ratios… “Decreases available energy”

Channel Narrowing Decrease Decrease width to depth ratios… “Increases available energy”

Channel Meanders Lengthening and Shortening - Channel Meanders Areas of maximum velocity causes erosion generating meander bends that move in a downstream direction

Channel Meanders Lengthening and Shortening - Channel Meanders

Famous Oxbow Lake in the Making!

Channel Meanders Lengthening and Shortening - Channel Meanders Lowers available energy Channel develops more meanders – “Lowers available energy” Increases available energy Channel develops less meanders – “Increases available energy”

Key Concepts! Discharge - Amount of water flowing in a river Slope– The inclination of the river channel Sediment Load – Sediment transported Vegetation – Along and within the channel Rivers only want the energy to transport their water and supplied sediment to ocean basins, and nothing more!

How do rivers adjust over time? Let’s do the Lab!!!

What do rivers do?

Things to Know:  HortanianSaturation  Hortanian versus Saturation overland flow  Stream Order, drainage basins, drainage divide fluvial sediment transport  Types of fluvial sediment transport  What is a river’s equilibrium gradient?  What alters a river’s equilibrium gradient?  How can river’s respond to channel change?  HortanianSaturation  Hortanian versus Saturation overland flow  Stream Order, drainage basins, drainage divide fluvial sediment transport  Types of fluvial sediment transport  What is a river’s equilibrium gradient?  What alters a river’s equilibrium gradient?  How can river’s respond to channel change? Help: Chapter FS