FLOOD Flashcards
Described as the volume of water moving
through a channel over a given time interval,
commonly measured in units such as cubic
feet per second (ft 3 /s)
Stream Discharge
to drain water off the landscape and to transport sediment
role of streams
a process where water flows through
stream channels
Runoff
precipitation reaching the land
surface moves downslope in thin sheets
Overland Flow
discharge of
groundwater into the surface environment
Groundwater baseflow
provide information about a
river or stream by simply plotting the discharge versus
time
Stream hydrographs
are a result of less deep infiltration in
arid areas resulting in a water table that is below the
level of most stream channels
Losing streams
are generally small and relatively fast
moving and occupy narrow valleys, but then evolve
Headwater streams
Individual systems are separated from one another by a
topographic high or crest in the landscape called a
drainage divide
represents the land area that collects water for an
individual stream or river.
drainage basin
are any smaller streams that feed larger streams within a
drainage basin
Tributaries
A method of classifying or
ordering the hierarchy of
natural channels
Strahler Stream Order
reflects downstream trade off between discharge
and slope in setting transport capacity (and thus ability to move
sediment and incise rock)
Longitudinal Profile
The
level below which a river or stream cannot incise
Base Level
Most commonly formed on horizontally
bedded and uniform sediments or on
uniformly resistant crystalline rocks.
Dendritic
Usually develops on moderate to steep slopes,
but also where regional structure, such as
outcropping resistant rock bands, are
elongated and parallel. All forms of transition
Parallel
Patterns most commonly on dipping or folded
sedimentary or weakly metamorphosed
sedimentary rocks; also areas of joints and
Trellis
Usually have a more or less
perpendicular turns mainly
caused by criss crossing
fractures.
Rectangular
Occurs around domes or cones, and
particularly common on volcanic areas.
Radial
Patterns also develop around domes, where
there exists alternating resistant and weak
beds, so that the major channels cut through
Annular
Can occur in a variety of conditions where local
hummocks and depressions inhibit a continuous
channel network.
Multibasinal
Incised into rocks with complicated structural
patterns. Associated with crystalline metamorphic
rocks with a history of intense folding, jointing,
intrusions, alterations, and faulting.
Contorted
all year agas na river
perennial
mo agas lang during heavy rain
ephemeral
naay month range para mo agas ni na river
intermittent
are loose rock particles/sediments
deposited on a stream.
Alluvium
One of the key factors in a stream’s ability
to erode the landscape is the
velocity of
the water
are unstable overhang located
at the outer bank which is produced by the
velocity increase on the outer bank which
subsequently enhances the ability of the
water to cut (erode) into the bank.
Cutbanks
On the inner bank where velocity decreases,
sediment tends to accumulate and form a
deposit known as a
point bar
the sediment that physically scrapes
or wears away rock in a process called
abrasion
Evidence for stream abrasion in solid rock can be seen in
potholes
The velocity of a particular stream segment is controlled
by the steepness of the channel, called
stream
gradient
is used to describe the lowest
level to which a stream can erode
base level
often referred to as ultimate base level
because the oceans represent the end or low point of
most rivers (exceptions include isolated areas below sea
level, such as the Dead Sea and Death Valley)
Sea level
describes the fraction of solid particles that is
in a suspended state and moving at the same velocity as the
water suspended material is what makes streams appear
muddy
Suspended load
The process whereby water separates sediment grains based
on their size, shape, and density is called
called hydraulic sorting
are mound shaped channel deposits consisting of sorted material ranging in size from boulders to
coarse gravel to fine sand.
Bars
develop on the inside of meander bends where water velocity
decreases.
point bars
are formed when a river enters a lake or ocean and splits into smaller channels and begins to
deposit sediment due to a decrease in velocity.
Deltas
are large fan shaped deposits that form where steep mountain streams empty
out onto valley floors at the mouth of rivers.
Alluvial fans
Streams also transport considerable amounts of dissolved ions (charged atoms) in what scientists refer to as the
dissolved load
produces wider valleys over time, whereas deposition on the
inner
banks helps to build a flat plain on the valley floor called a
natural floodplain.
are pair of ridges that run parallel to the bank
which are formed due to the deposition of sediment, commonly
sand, at the edge of the bank.
Natural levees
are areas on the floodplain that are poorly
drained and can remain wet long after a flood.
Back swamps
are old floodplain left high and dry as river
migrates.
Stream terraces
The potential for flooding in a given area naturally increases as the_________ and _______ of rainfall
increases. Rainfall events range from light, steady rains that may last for days to heavy, and torrential rains
intensity and duration
The ability of the ground to absorb water, referred to as
infiltration capacity,
are floods that have short duration
with relatively high peak discharge; small
streams and rivers tend to rapidly overflow
their banks.
Flash Floods
can be defined as one where a river
leaves its channel farther down in its drainage
basin, flowing out onto its floodplain and
inundating large areas of the valley floor.
Downstream Floods
normally dry areas of
the land become inundated
flood
the height at which a river
begins to overflow its banks.
Flood stage
straightening and deepening a stream channel
Channelization
temporarily stores some the excesses water in a
series of depressions
Retention Basins
type of barrier in which
vegetated strips line the banks of stream channels,
Stream buffers
made of a synthetic
fabric that is fi ne enough to trap sediment,
silt fences,
Wetlands (swamps) are commonly found in
topographic depressions and adjacent to river channels, in
which case they are called
riparian wetlands
Large pipes called _____ are typically used
for small streams that flow intermittently.
culverts
