FLUVIAL PROCESSES

1. FLUVIAL PROCESSES • STREAM FLOW • STREAM HYDROGRAPH • EROSION, TRANSPORT & DEPOSITION

2. STREAM FLOW • Stream flow (discharge) usually expressed in Cubic Meters per Second (CMS) or CFS. • Discharge commonly measured in the field. • Stream width (m or ft), depth (m or ft), and the flow of water (m/s or ft/s) at a cross-section of a stream. (Q = WDV) • Stream flow is a rate of the amount of water moving past a given location per unit of time.

4. DISCHARGE: Q=AV • discharge = area (WxD) x velocity

5. Erosion, Transportation and Deposition

7. Stream Erosion • Detachment of material from the bed or sides of the channel • Flowing water erodes in three ways • Solution (Corrosion) • Abrasion (Corrasion) • Attrition • Hydraulic action

10. Stream Hydrograph

11. Stream Transportation • Transportation is the movement of earth material, in this case, by water. • As particle size increases, so does the velocity needed to transport it. • Transport depends on an appropriate balance of forces within the transporting medium.

12. Besides velocity what else might play a role in the particle size that is moved? • Slope • Steeper the gradient larger the particle sizes • Less steep gradients smaller particle sizes

13. SEDIMENT TRANSPORT

14. Once a particle is entrained, it tends to move as long as the velocity of the medium is high enough to transport the particle horizontally. Transport can occur in four different ways: • Suspension • Saltation • Traction • Solution • Particle weight, size, shape, surface configuration, and medium type are the main factors that determine the process.

15. Stream DEPOSITION • Reduction in slope, velocity and discharge results in fall of ability to move sediments and hence deposition. • Deposition results in distinct landforms (We’ll discuss these in next class).

16. Normal Flow Flood: Increased discharge and erosion! Post-flood; new bars deposited

17. GENERAL CONCLUSIONS Low Order Streams Intermediate Order Streams High Order Streams