Fluvial Systems GPH 111 What are Fluvial Processes

Fluvial Systems GPH 111

What are Fluvial Processes? w 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 - Mountains weather and erode, rivers then transport the debris to the sea. 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? Too Full! – Upset passengers, not enough fuel or flights to transport customers Equilibrium - Just enough fuel to carry planes full of passengers to their destinations and nothing more – Happy Company! Too Empty! – Upset passengers, too much fuel or too many flights to transport customers. Similar to an airline that tries to fill all seats for their flights, no MORE or LESS.

How do rivers adjust over time?

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

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

Channel Incision

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

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

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

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

Lengthening and Shortening Channel Meanders

Lengthening and Shortening Channel Meanders Famous Oxbow Lake in the Making!

Lengthening and Shortening Channel Meanders Channel develops more meanders – “Lowers available energy” energy Channel develops less meanders – “Increases available energy” 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: w Hortanian versus Saturation overland flow w Stream Order, drainage basins, drainage divide w Types of fluvial sediment transport w What is a river’s equilibrium gradient? w What alters a river’s equilibrium gradient? w How can river’s respond to channel change? Help: Chapter FS