1. River System Development
runoff eventually works its way into a river system
water runs off the ground and enters a small stream
small streams (called tributaries) join to form a large stream

2. where large streams join, a river forms
this joining of tributaries into a single large river occurs in a drainage basin
tributary

3. drainage basin: land area where all the water runs into one large river

4. different drainage basins are separated by a divide
divides tend to be high elevation areas like the top of a mountain

5. beginning of a stream is called its headwaters
end of a stream (where it enters a large body of water) is called its mouth

6. will see fan-shaped sediment deposits called deltas at the mouths of rivers

7. fan-shaped sediment deposits ON LAND are called alluvial fans
these form in dry regions when there are temporary streams

8. Stages in River Development
can classify rivers in one of three stages:
Young
Mature
Old

9. young: “V” shaped valley
straight, narrow channel
steep slope (called the gradient)
many rapids

10. carries all sizes of sediment
due to fast water flow & high volume of water (called discharge)
down cutting erosion making river deeper

11. mature: valley widens
begins to curve (called meanders)
begins to develop a floodplain, the flat area next to banks of channel

12. carries medium & fine sediment due to lower discharge
side cutting erosion making the river wider

13. old: “U” shaped valley
valley walls replaced by floodplain
large meanders (curves)

14. many oxbow lakes which are cut off meanders that form when the river floods
this happens because water wants to go in a straight line!

16. carries only fine sediment due to very low discharge
forms many natural levees which are wall-like sediment deposits along banks