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4.1 Surface Water Objectives: Identify the causes of runoff. Compare rill, gully, sheet, and stream erosion. Identify three different stages of stream development. Explain how alluvial fans and deltas form.

Module G, Chapter 4: Water Erosion and Deposition

Runoff Runoff is water that does not soak into the or . ground It flows into streams, lakes or oceans. ground evaporate

Factors that Effect Runoff: amount of rain time vegetation slope

Gravity Earth energy erodes Gravity pulls water toward the . As the water moves, it builds and the surrounding rock and soil. energy erodes

After heavy rains, form and Rill Erosion ________________ ________ the land. small streams erode

deeper and wider forming . Gully Erosion Over time, become deeper and wider forming . rill channels gullies

water flows into lower elevations carrying sediments with it. Sheet Erosion Over a , rain water flows into lower elevations carrying sediments with it. flat area

Stream Erosion When a stream forms, the water continues to pick up sediments from the and of the channel. bottom sides

River System Development gullies Water from __________, __________ and ______________ located upstream flow into larger streams which flow into rivers. rills small streams

Drainage Basins land area A drainage basin is a from which a or gets its water. The largest drainage basin in the USA is the . stream river Mississippi River

Stages of Stream Development!!! 1. Young 2. Mature Old 3.

Young Streams quickly flow ______________ have ________ sides whitewater rapids water falls have a high level of ___________ erode the ____________ steep energy bottom

Mature Stream Mature streams flow _____________ and most of the larger rocks have eroded away. It also erodes away at the ____________ rather than the bottom. This causes it to develop curves also known as ___________. less swiftly sides meanders

Old Stream Old streams flow ___________. They are __________, ___________ and flow into flood ___________ . slowly broad flat plains

Deposition by Surface Water alluvial fan An ___ is made by sediments being dropped as a river flows on a level surface and slows down.

Named after the Greek letter Delta = ∆ Deltas Named after the Greek letter Delta = ∆ Sediment that is deposited as water empties into an _________ or __________ forms a triangular, or fan-shaped deposit called a __________. ocean lake delta Nile Delta

Check for Understanding 1. Explain how the slope of an area affects runoff. 2. Compare and contrast rill and gully erosion. 3. Describe the three stages of stream development. 4. Compare and contrast the formation of deltas and alluvial fans.