Surface Water Movement & Stream Development

1. Surface Water Movement & Stream Development Chapter 9.1 - 9.2

3. Surface Water Movement • Once water reaches the Earth, what happens to it? • Runoff – water flowing downslope along Earth’s surface • Can reach a stream • Can evaporate • Can infiltrate Earth’s surface to become groundwater

4. Surface Water Movement • What conditions determine whether water will infiltrate the surface? • Soil composition • Pore spacing & percentage of particles • Soils w/ lots of sand, infiltrate; lots of clay – harder to infiltrate • Rate of precipitation • Light, gentle infiltrates more than heavy downpour. • Vegetation – more is better • Slope – gentle to no slope is better for infiltration

5. Stream Systems • Streams – surface water channels • Tributaries – streams that flow into other streams • Watersheds – all of the land area whose water drains into a stream system

6. Georgia Riverbasins

7. Stream Load & Carrying Capacity • Stream Load: the amount of material a stream carries • Load is carried in 3 ways • Materials in suspension • Particles small enough to be held up by the turbulence of the moving water • Bed load • Sediment too big to be suspended, but is rolled or pushed along by the moving water • Materials in solution • Materials dissolved in the stream’s water • Expressed in parts per million (ppm) • Carrying capacity is the stream’s ability to transport material. • Depends on velocity and amount of water in stream • affected by channel’s slope, depth, and width

8. Stream Development • Headwaters – region where water first accumulate to supply a stream • Usually high in mountains • Stream channels – the path of a stream, with water held within its banks • Meanders – bend or curve in a stream channel caused by moving water

9. Visualizing Erosion & Deposition in a Meander Click on picture to animate

10. Visualizing Stream Development Click on picture to animate

11. Deposition of Sediment • The velocity of a stream determines how much sediment it will transport and subsequently the loss of velocity dictates how much of that sediment will deposit out of the stream • Alluvial fans – in mountainous regions where the gradient suddenly decreases, the sediment is dropped quickly at the base of the mountain in a fan-shaped deposit. • Deltas - triangular deposit that forms where a stream enters a larger body of water