Chapter 16 Floods

most common ares to find a braided stream or river

- broad, sloping plains that flank mountain ranges - flat-bottomed valleys between mountains

channel beds erode faster than channel sides in ____ streams and rivers

- highly turbukent - high velocity - high gradient

what factors of a drainage basin influence the flow response to rainfall

- shape - size - slope

chracterists of a braided river system

- steep gradient - variable flow - abundant sediment

rank in order from the beginning the process necessary to create entrenched meanders

1. a meandering river flows across a floodplain 2. a tectonic event causes uplift, causing the river to erode downward 3. further incision by the river creates more entrenchment

particle sizes transported by water from the smallest to largest

1. clay 2. silt 3. sand 4. cobbles 5. boulders

the formation of terraces by rivers from the first stage at the top

1. deposition of sediment occurs on the floodplain 2. a drop in the base level of the river results in downcutting through deposits 3. fruther downcutting occurs, and the river abandons the previously formed floodplain 4. the oldest floodplain becomes isolated as the river downcuts, leaving a terrace

two ways that mountain streams obtain their sediments

1. soil and/or sediment slides down into the drainage area 2. tributaries bring sediments into the drainage area

lowest discharge by season to the highest for a river in the upper midwest

1. winter 2. fall 3. summer 4. spring

the erosion base levels of a river are

a closed land basin an ocean a lake

what is a drainage divide

a ridge or strip of high ground separating one drainage basin from another

point bar

a sandbar deposited along the inside of a stream meander due to lower velocity

braided stream

a stream that flows in a network of many interconnected rivulets around numerous bars

the lowest level to which a river can erode is its

base level

flat bottomed valleys between mountains would be good places to look for ____ rivers or streams

braided

tectonism

can increase the slope and supply of coarse sediments

dam

changes the base level because of the sediment buildup

dissolved

chemically soluble ions transported by the river

suspended

clay and silt carried indefinitly above the riverbed

besides sea level and rock type, the other two primary factors that influence a stream or rivers profile are

climate tectonics

formed as rivers slow down when they reach their mouth and empty into an ocean

deltas

_____ drainage patterns are associated with ares where rocks have the same resistance to erosion

dendritic

the amount of water flowing through a channel over a given amount of time is called

discharge

radial drainage pattern

drainage is found on symmetrical mountains like volcanoes

structurally controlled pattern

drainage occurs on eroded layers or structures and then cuts across a ridge to follow a differnt weak layer

the water velocity is faster and causes____, and the water velocity is slower, which causes ____

erosion; deposition

a broad strip of land on either side of a stream channel that is covered by water during a flood and replenished by sedimentation

floodplain

viscosity is the resistance to ___ exibited by fluids

flow

the change in elevation for a given stream or river over a horizontal distance

gradient

the force behind a rivers flow from high to low elevations

gravity

the area of the origin of a river is its ____, and the ____ the end of the river

headwaters; mouth is

runoff

increase flow, causing flooding

bed

material carried on the bottom of a river by pushing, bouncing, rolling, and sliding; usually sand and gravel

a stream or river that flows all year long is referred to as

perennial

_____ drainage pattern are found on symmetrical mountains

radial

measurements needed to calculate discharge of a river at a certain point

river width river depth velocity of the water

erosion and deposition by ____ are the principle processes that sculpt earths landscape

rivers

the type of sediment transport that involves a series of leaps or bounces off the bottom of a steamed is known as

saltation

the amount that a river or stream channel curves in a given length

sinuosity

factors of a drainage basin influence the flow response to rainfall

slope size shape

a river ____ is formed as a river incises into the surrounding rocks and sediments, leaving a record of the rivers historical size and location

terrace

river ____ are relatively flat benches that are perched above a river or stream and that stair-step upward and outward from the active channel

terraces

sinuosity

the amount that a river or stream channel curves in a given length

dendiritic drainage pattern

treelike pattern developed on rocks with similar resistance to erosion

flowing ____ is the most important geologic agent in eroding, transporting, and depositing sediment.

water