1. RIVERS!!!!!!!! (and valleys)
Chapter 12 (page 39)

2. Because Bill Nye always makes things better…

3. Drainage Basins, Streams, Rivers
A drainage basin (watershed, catchment) is a piece of land where water (rain and melting ice) drains into a larger body of water. Includes the streams, rivers and channels  OPEN SYSTEM separated by divides
When water accumulates upland, and flows along a definite course, they are called streams
Small streams  tributary streams
Tributary streams flow down and join together to connect to a river

4. Drainage Basin

5. Types of drainage patterns
The hardness of the rock layers in the region determines the formation of certain drainage pattern that results
There are three types of drainage patterns

6. Drainage pattern #1: Dendritic
Most common pattern
Resembles vein or tree branch pattern
Forms on flat surfaces where the rock layers are of uniform hardness
Form in v-shaped valleys where many small tributaries join together and then join onto a main river, giving it the appearance of a tree

8. Drainage pattern #2: Trellis
As a river flows down a valley, smaller tributaries flow into it from steep mountain slopes
Tributaries enter the main river at approximately 90 degree angles, causing a trellis-like appearance of the drainage system
Trellis drainage is characteristic of areas with alternating parallel valleys and ridges, and folded mountains

10. Drainage pattern #3: Radial
The streams radiate equally outwards from a central high point
Volcanoes (as well as domes and laccoliths  Cone-shaped mountains) usually display excellent radial drainage

11. River Valley shapes Dry (arid) regions  steep slope  forms canyons
(vertical erosion)
Wet regions  gentle slope  heavy sediments in water

12. Four stages of a River development
Youth stage
Mature stage
Old age stage
Rejuvenated stage

14. Stage #1: Youth Stage
River cuts a deep V-shaped valley (steep gradient)
Flows in highlands of mountainous areas with very little shifting of its channel
Usually small in size
Dominated by erosion  fast, violent water  little deposition
Little floodplain, but rapids, waterfalls, and boulders may be found

15. Stage #2: Mature Stage Receives the waters of many tributaries
River increases in size and slows in velocity  more deposition
Eroded the bed downward and gotten closer to the base level
Though it is still eroding downwards, it mainly erodes laterally to form meanders and eventually flood plains

16. Stage #3: Old Age stage Extensive meandering forms oxbow lakes
Its gradient and speed are very slow,
Because of this it has lost the power to erode downwards and carry as much sediment load  deposits rich alluvium on the floodplain

17. Stage #4: Rejuvenated stage
River returns to the youthful stage
Vertical erosion creates v-shaped valley and process starts again

18. The four stages

19. Erosional action of rivers (4 types)
THIS SHOULD BE FAMILIAR!!! 
Hydraulic action
Abrasion
Attrition
Corrosion

20. Ways that rivers transport sediments
THIS SHOULD BE FAMILIAR!!!
Solution
Suspension
Saltation
Traction

21. Rivers PART TWO!!

22. Landforms associated with upland rivers
Steep gradient (steep slope)
Water flows swiftly with vertical erosion
Waterfalls occur where rocks have eroded quickly
Igneous rock wears out much slower than others (e.g. sedimentary rock)

23. Potholes, Gorges and Canyons
Potholes develop along river beds
Pebbles get trapped
Water spins and abrasion deepens the hole
Eventually a gorge or even a canyon may result (narrow slot in landscape)

24. Landforms associated with lowland rivers
When the river has reached an elevation close to the sea level, a flood plain may result
Lateral erosion and energy
River can flow overflow and deposit rich alluvium (ideal for farming)

25. Meanders, undercut banks and slip-off slopes
Erosion is greatest and fastest along the outer edge of a meander (bend)
Undercut bank (outer edge)
Point bar/ slip-off slope (inner bank)

26. Levees and dikes
Levees: mounds of sediment that slowly build up along the river bank
Hold in flood water
Natural dikes
Common in valleys where river cannot carry all of its load
Dikes: artificial levees created to minimize flooding

27. Mississippi River floods of 1993

28. River terraces
Lowland regions sometimes uplift and the meandering river begins vertical erosion again
Once uplifting stops and a flood plain is formed, lateral erosion is once again dominant
The old, uplift flood plain sits high above river banks
These ledges are called river terraces
Let’s draw it out!!! 

29. Braided river channels
Sand and gravel “islands” may break up the water flow, so rivers take on a braided appearance
Transport large volumes of debris  when deposited, creates sand bars and islands

30. River deltas
A river carries sediment from its drainage basin into the ocean
Current carries them into the ocean before they are deposited
Sand (heavy)  silt  clay (light)
Large rivers have broad deltas with shallow water extending far into the sea
Very gentle slope
Waves cannot erode as effectively

31. 3 main types of delta Arcuate delta Bird’s foot delta Estuarine delta
LOOK ON PAGE 190 OF BLUE GEOGRAPHY BOOK FOR AWESOME ILLUSTRATIONS FO DELTAS AROUND THE WORLD!!! 

32. Arcuate delta
Carries water and sediment across a symmetrical delta in distributaries
Inverted cone shape
EX. Nile River Delta

33. Bird’s foot delta
Many distributary channels branch out from main river channel
Bird’s foot shape
EX. Mississippi River Delta

34. Estuarine delta
Forms when river sediment is deposited in a submerged river mouth
Estuary shape