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