Water Erosion

• Where does a river get its water?• Where does this water ultimately come from?

• Moving water is the major agent of erosion that has shaped Earth’s surface

• Water can pick up soil particles and move them (erosion) or drop them off (deposition)

• Water that moves over Earth’s surface is called runoff

• Five factors that affect amount of runoff:– Amount of rain– Amount of plants– Type of soil– Shape of land– How people use the land

• A gully is a large groove, or channel, in the soil that carries runoff after a rainstorm

• A stream is a channel along which water is continually flowing down a slope

• A tributary is a stream that flows into a larger stream

Gully

Tributary

Erosion by Rivers

• A river creates valleys, waterfalls, flood plains, meanders, and oxbow lakes

• Rivers create “v-shaped valleys”• The flat, wide area of land along a river is

called a flood plain

• A bend in a river is called a meander • Sometimes a meander can be cut off to form

an oxbow lake

Deposition by rivers

• Deposition creates alluvial fans and deltas

Alluvial Fanwide, sloping deposit of sediment formed when stream leaves

mountain

Delta Sediment where a river meets the ocean

• How can water move soil and sediment?• In what ways do rivers flow?• Where would you find a delta in the United

States?