A flash flood is a heavy flow of water over a river's banks that occurs faster and with more force than typical flows. Flash floods can cause significant erosion and deposition. Experiments using stream tables show that flash floods lead to faster, deeper, and more extensive erosion and deposition compared to typical flows. Increasing the slope of a stream table results in faster water flow that causes greater erosion.

1. Experiments in Erosion and Deposition Flash Floods and Slippery Slopes!

2. What is a flash flood? Both slides were taken at 30 seconds. Which one shows a flash flood? That’s right. The one on the right.

3. A flash flood is a very heavy flow of water which is greater than the normal flow and goes over the banks of the stream or river’s normal channel.

4. The Jamestown Pennsylvania Flood 1889 This famous flash flood was cause by days of extremely heavy rains and the failure of a dam upstream. Over 2200 people lost their lives.

5. How do flash floods affect erosion and deposition? Faster ! Deeper ! Bigger! Erosion happens faster. Channels are straighter. Canyons are deeper and wider. Deltas are wider and longer. Control Flash flood

6. Time Elapse Log 10 seconds Flood plain forms. Cliff edge beginning to slump. 30 seconds No change. 1 minute Delta begins to form. 10 seconds Hole under water source. Cliff edge crumbling. 20 seconds Steep canyons form. 30 seconds Large delta forms. 1 minutes Water has drained from the hole. Control Table Flash Flood Table

7. Which is the flash flood? Which is the control? control Flash flood!

8. Two Flash floods, one control Flash Flood! Flash Flood! control

9. The Effect of Slope on Erosion and Deposition This slide shows how the stream table looked after about 30 seconds. This slide also shows a stream table after 30 seconds. What differences do you notice? What could account for these differences? control slope

10. What happens when water falls down a incline or runs over a tilted surface? It goes faster and has more force to increase the speed and degree of erosion .

11. Faster, deeper, bigger These two slides were both taken at about 3 minutes elapsed time. Which stream table do you think was level? Which one was placed on a slope? slope

12. One slope, one control Slope Control

13. Conducting Experiments What do you think would happen if we increased the slope and had flash flood conditions? What else might you want to learn about erosion and deposition? How can we find out?