Bonneville Flood Walters Bar Area
suggested grade levels: 9-12
view Idaho achievement standards for this lesson
View the map and answer the following questions:
1. Determine the maximum water level height of the Bonneville Flood at high water stand.
2. Locate the pendant bar on Walters Bar. How did the pendant bar form and the resulting Jensen Lake?
3. Provide an explanation for the thick deposits of sand on the north side of Walters Bar.
4. Use the following photographs: * wb#4wabu.jpg * wb#5wabu.jpg * wb#9wabu.jpg
to determine the height of the boulders that were deposited on Walters bar by the Bonneville Flood. (Use Sara for scale, height = 5'5" Note you will need to convert feet to meters.) Click here for some useful conversion tables.
5. Use Hjulströms diagram to determine velocity of water needed to move boulders that were deposited on Walters Bar. Note: You may have to extrapolate on the Hjulströms diagram to determine the velocity.
6. Conduct a survey of boulder size on Walters Bar demonstrating water velocity decreased from proximal to distal portion of bar. (note: may want to incorporate the boulder size database).
7. Measure the width of the canyon at the Can-Ada Counties border. Measure the width of the canyon on the western most portion of the map near Walters Ferry. What is the difference between these two measurements? How did the canyon width control flood water flow and how does this relate to the production of the resultant features?
8. See figures wb#2wabu and wb#3wabu. Define festoon crossbedding. How are festoon cross stratification formed? Determine the relative thickness of the entire gravel unit and also the thickness of one cross bed. (You can use Sara once again for scale) Describe the flood mechanism that formed this deposit. Determine the velocity of the flood water that deposited such a thick series of cross stratification.