Students conducted physical geography fieldwork to investigate downstream changes along a river channel. Below is a summary of the data they collected at 4 sample sites from the source downstream.
| Site | Distance from Source (km) | Channel Width (m) | Mean Velocity (m/s) |
|---|---|---|---|
| 1 | 1.2 | 1.4 | 0.25 |
| 2 | 4.5 | 3.8 | 0.42 |
| 3 | 9.1 | 7.5 | 0.58 |
| 4 | 15.3 | 12.1 | 0.72 |
Identify two further pieces of primary physical data that the students could collect at these sites to investigate fluvial processes and channel characteristics.