Experiments in Erosion and Experiments in Erosion and DepositionDeposition

Flash FloodsFlash Floods and Slippery Slopes!

What is a flash flood?What is a flash flood?

Both slides were taken at 30 seconds. Which one shows a Both slides were taken at 30 seconds. Which one shows a flash flood? flash flood?

That’s right. The one on the right.

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.

The Jamestown Pennsylvania The Jamestown Pennsylvania Flood 1889Flood 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.

How do flash floods affect erosion How do flash floods affect erosion and deposition?and deposition?

Faster! Deeper! Bigger!Erosion happens faster. Channels are straighter.Canyons are deeper and wider.Deltas are wider and longer.

Control Flash flood

Time Elapse LogTime 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

Which is the flash flood? Which is the control?Which is the flash flood? Which is the control?

control Flash flood!

Two Flash floods, one controlTwo Flash floods, one control

Flash Flood!

Flash Flood!

control

The Effect of Slope on Erosion and The Effect of Slope on Erosion and DepositionDeposition

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

What happens when water falls down a incline or What happens when water falls down a incline or runs over a tilted surface?runs over a tilted surface?

It goes It goes faster faster and has more and has more

force force to to

increase the increase the

speedspeed andand

degreedegree of of

erosionerosion..

Faster, deeper, biggerFaster, 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

One slope, one controlOne slope, one control

Slope Control

Conducting ExperimentsConducting 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?