Section 14: River Systems and Landforms

SLOs: fluvial processes and drainage basins, flow and channel characteristics, floods.


Lesson 1:

Instruction

Fluvial, or river, processes erode, transport, and deposit sediments (alluvium) along waterways.  Every waterway has a drainage basin, or watershed, in which water and sediments are eroded, transported, and deposited into the same general location.  These watersheds can be small or large, and can be subdivided based on the scale at which analysis takes place.  In Ventura County, an example of a relatively small drainage basin is that which supports the Ventura River.  In the United States and Canada, an example of a relatively large drainage basin is that which includes all waterways and sediments on the west side of the continental divide (characterized by the highest elevations of the Rocky Mountains).  Both of the watersheds described empty into the Pacific Ocean.                 

Photos and Images
 (small watershed)     (large watershed)

Quiz

Use Google Earth, or go to the Ventura County Watershed Management District (http://www.vcwatershed.org), to find other small watersheds in Ventura County.  Name three.

 


Lesson 2:

Instruction

Discharge is the rate of a waterway's flow: Q = wdv (where Q = discharge, w = channel width, d = channel depth, and v = stream velocity).  Using this equation, hydrologists can determine many things about a river, stream, creek, or other waterway.  If a waterway has a large channel (width and depth), as well as a high velocity, then it will surely have a large amount of discharge.  There are also multiple flow and channel characteristics.  The two types of flows are laminar and turbulent.  Laminar flows occur in waterways with low velocity that exhibit parallel flows of water.  Turbulent flows occur in waterways with high velocity that exhibit non-parallel flows of water.  The three types of channels are braided, straight, and meandering.  Braided and straight channels are named after the physical appearance of the water flows, whereas meandering channels appear snake-like (with large curves and banks).  In Ventura County, braided and straight channels are predominant.          

Photos and Images

 

 

 (braided channel, Santa Clara River) (straight channel, Ventura River)

Quiz

Given the equation: Q = wdv, where a hypothetical channel width, depth, and velocity is large/high; what type of flow would you expect to have?

 


Lesson 3:

Instruction

Flooding is a big concern for people during winter storms here in Ventura County.  A flood happens when water levels rise to overflow the levees (banks) in any waterway.  To determine flood hazards to people, waterway management agencies create hydrographs (stream discharge graphs).  These graphs help management agencies to determine peak flow rates that are predicted to occur during major storms.  All terrain that becomes inundated by water during peak flows is termed a flood plain.  Thus, when flooding is eminent, the flood plains become very dangerous ground.       

Photos and Images
   (flood plain) 

Quiz

Because of housing shortages in Ventura County, the city of Santa Paula recently allowed a developer rights to build homes in the Santa Clara River flood plain.  Do you think this is a good or bad idea?  Why?    


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2006 Jessica Douglas