Notes: Ch 13 Rivers
 Almost half of the water that falls to the Earth’s surface eventually ends up in a stream or river (RUNOFF) where it travels overland to the oceans.
 Rivers account for most of the erosion of EARTH’S SURFACE
 Rivers can be divided into 3 main sections.
 Rivers usually begin in the MOUNTAINS (source)
 They flow downhill onto flat land and into the
OCEANS (mouth)
3 STAGES OF RIVER DEVELOPMENT
YOUTHFUL – STEEP SLOPE
MATURE - MODERATE
OLD - GENTLE
YOUTHFUL RIVER STAGE

STEEP slope or gradient

STRAIGHT narrow channel

VERY FAST moving water

‘V’ - shaped valleys
 Many rapids & waterfalls – caused by STEEP SLOPES &
DIFERENTIAL EROSION

Youthful Rivers will carve a V-SHAPED valley
 [Glaciers will carve a U-SHAPED valley]
MATURE RIVER STAGE
 River channel starts to WIDEN

Some rapids and WHTIEWATER

FAST flowing water
FORMATION OF A MEANDER
SLOW moving water
INSIDE curve
Deposition will occur on the inside of a meander to create a POINTBAR
 River starts eroding OUTWARD

MEANDERS and floodplain start to develop
FAST moving water
OUTSIDE the curve
Erosion on the outside of a meander will create a CUT BANK

OLD RIVER STAGE
 Move very SLOW
 Has a nearly FLAT slope
 Wide FLOODPLAIN
 Lots of MEANDERS
 OXBOW lakes
MEANDER & OXBOW LAKE FORMATION
A river wants to find the shortest, straightest way to the ocean, so it will change paths along the floodplain cutting off wide loops leaving behind a curved body of water called an OXBOW LAKE.
FLOODS!

Rivers may overflow its banks as a FLOOD. The floodwater may cover part or the entire valley floor where the river runs eroding and depositing sediments.

This part of the valley floor is called the FLOODPLAIN.

Floods can ERODE or DEPOSIT.
FROM VALLEY TO FLOODPLAIN
 Flooding speeds up erosion and deposition creating a broader floodplain on the valley floor.
 Elevated ridges along stream banks are called
NATURAL LEVEES.
PARTS OF A RIVER SYSTEM

A TRIBUTARY is a stream that runs into a larger stream.

The main river will eventually drain into the OCEAN

A river and all of its tributaries is called a RIVERSYSTEM

The beginning of a river is known as the SOURCE. Begins from a spring or precipitation.

When the mouth of a river finally reaches its destination, be it ocean or lake, the water slows down & deposits its sediment, forming a DELTA.

An ALLUVIAL FAN is similar to a delta, but forms on land where a river emerges from a mountainous area and flows out onto a more gently sloping plain.

Notes: Ch 13 Rivers (page 2)
DRAINAGE BASINS or WATERSHEDS
 The drainage basin, or WATERSHED, of a river includes all the land where rain falls that drains into the river directly or through its tributaries.
 A watershed is like a PRECIPITATION COLLECTOR!
 Every drop of water or POLLUTION that falls into the watershed goes into that river.
 There is an INCREASE in storm water RUNOFF with urbanization.

There is a DECREASE in INFILTRATION with urbanization.
DIVIDES

High land (mountains) that separates one drainage basin from another is called a DIVIDE.
 The major divide in the U.S. is called the CONTINENTAL.

The MISSISSIPPI Drainage Basin is the largest watershed in the U.S.
DRAINAGE PATTERNS
DENDRITIC is the most common
DENDRITIC RECTANGULAR
RADIAL
3 MAJOR WATERSHEDS OF VIRGINIA:
1. CHESAPEAKE BAY
2. GULF OF MEXICO (via MS River)
3. NORTH CAROLINA SOUND
Largest Localized Watershed in Virginia: JAMES RIVER
TRELLIS