DRAINAGE BASIN EVOLUTION IN RESPONSE TO OVERLAND FLOW AND RAINFALL SIMULATION

How sediment flux varies as a drainage basin evolves is an interesting question which has inspired decades of research. This study looks at sediment flux in a small (0.5 m x 0.5 m) experimental basin where the basin evolved around a single base level drop. Two sets of experiments were performed to distinguish if any differences exist between an experimental set up using rainfall simulation and an experiment using overland flow. The results showed that while there are some differences between basin evolution in an overland flow model and a rainfall model, in general sediment flux decreases or remain constant in response to a single base level drop. Increases in sediment load occasionally occur in response to stream piracy or mass wasting events, yet after these events sediment flux quickly returns to the previous constant value. The sediment flux measurements made during these experiments indicate that in watersheds evolving in tectonically inactive areas, where base level is not constantly changing, increasing sediment flux is unexpected and may be a result of anthropogenic influences.