Purpose: Discover conditions needed for water to move stones of various size.
Materials:
Procedure: Pick an easy public access area on a river, preferably one with riffles and fairly fast-flowing water, and one not frequented by others (to minimize the risk of stones getting kicked or moved by humans). Attach surveyor tape to a tree, or stick it into the ground on a metal rod, if there is no permanent close-by fixture to use for compass readings. Students place the three stones in the river, taking careful measurements of the distance and compass reading of each stone from the surveyor's tape. Visit the site at intervals and remeasure the position of the stones. The students should also measure the river's velocity on the day they place the three stones and when they come back to check on the movement of the stones.
A data sheet might look something like this:
| date | velocity (fps) | from marker: | 4" stone | 1.5" stone | 0.5" stone |
| distance | |||||
| compass reading | |||||
| distance | |||||
| compass reading | |||||
| distance | |||||
| compass reading |