DETERMINING WHETHER RIPPLES WERE DEPOSITED BY A CURRENT, WAVE ACTION, OR COMBINED FLOW...


 

Copy of Starting  Photo 1: Dr. Isbell explains the different types of ripples and how to calculate ripple indices to Jim, Carrie, Quinton, and Joe.  Ripples may be deposited  by:
  • A Current
  • Wave Action
  • Combined Flow--may be current-dominated or wave-dominated
 We can determine how  ripples were deposited by:
  • Calculating the ripple index
  • Calculating the average ripple index
  • Interpreting the results

 Photo 2: (Left to right) Joe, Jim, Quinton, and Gina try to find ideal ripples to measure at  Laurel Lake Spillway in Kentucky.		 STEP 1: Choose a good ripple to measure.  A good ripple is an "average" ripple, or a ripple that is representative of a particular location.

ripple1_drawing STEP 2:
Determine the stoss and lee sides of the ripple. The stoss side has a gentle slope, and the lee side has a steep slope.  The stoss and lee sides also help you determine the direction of flow.

ripple2_drawing STEP 3:
Take the measurements of the stoss side length, lee side length, and  height.  Our class made pencil marks on the actual ripples so we knew where to start and end our measurements. 

Reading_height
 Photo 3:  Measuring ripple height using the "Ripple Measuring Instrument." 		 How To Take Measurements:


Ripple length and height can be determined by using the "Ripple Measuring Instrument" as shown in the photo on the left.  The ripple height in the photo is about .75 cm.

table_RI STEP 4:
Calculate the ripple indices where: 

L = ripple length (stoss side + lee side) 

H = ripple height 

L / H = ripple index 
 
 

Note: all of our measurements were taken in centimeters.

Interpreting_results
Photo 4: Kim recording and interpreting data.		 STEP 5:
Interpret your results. 

If the average ripple index is: 

  •  < 4, the ripples were deposited by wave action.
  •  > 15, the ripples were deposited by a current.
  • 4-15, the ripples were deposited by combined flow.


Our Conclusions for the ripples found at Laurel Lake Spillway: 

**The average ripple index was 8.33, which means they were most likely deposited by combined flow.
 

This page was created by: Carrie Elizabeth Check (10-28-03).

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