Hydrologic cycle
a continuous transfer of Earth's water from the ocean to the atmosphere to continents back to the ocean
Streams-fluvial environment
running water confined within a channel or a series of channels
Laminar flow
Smooth flow of fluid in parrallel layers with no disturbance between the layers; this can be a smooth straight line flow or curvilinear flow
Stream discharge
the quantity of water that passses a cross-sectional area in a given interval of time
Discharge=
channel width x channel depth x stream velocity = m cubed per sec/ or ft cubed per sec
stream transportation list
load:
1. Dissolved load
2. Suspended load
3. Saltation
4. Bed load
Dissolved load
comprises half of the total world load
Suspended load
sediment carried above the stream bed by flowing water
Bed load
sediment is physically shoved, rolled, bounced on stream bed
Aggradation
stream deposits its excess load in the stream bed
Degradation
stream erodes its own channel
base level def: and list:
lowest level at which a stream can erode its own channel
1. local base level
2. sea level
local base level
lake, pond, reservoir, or juncture (confluence) of two streams
sea level
ultimate base level
Stream discharge lists
1. "normal flow"
2. bank full discharge
3. flooding
flooding
overbank deposition during floods causes vertical accretion
flood discharge
the point where the water overflows the channel
what are the 3 major paths by which water on slopes can be transported to the stream environment and exported from the drainage basin?
1. overland flow
2. throughflow
3. groundwater flow
throughflow
a type of shallow subsurface flow above the groundwater table
drainage basin
an area of ground in which any precipiation falling in the watershed will leave in the same river or stream
drainage density equation
D=L/A
D (drainage density)
L (total length)
A (total area)
D is expressed as
having units of the reciprocal of length (1/L)
drainage density is a measure of?
how well or how poorly a watershed is drained by stream channels.
A high value of drainage density would indicate?
a relatively high density of streams and thus a rapid storm response
typical drainage density values range from?
1.5 to 6 mi/mi sq
floodplain
area adjacent to the stream channel which is periodically inundated by water and sediment
floodplain features
meanders, point bars, cut-banks, cut-offs, oxbow lakes, oxbows, Yazoo streams, delta
delta
depositional plain formed at the mouth of a river
distributaries
stream braks up into many channels across a delta
what happens to distributaries during floods?
during floods when the river overflows its banks, it loses velocity as it spreads out and drops a portion of its sediment load to form levees
the length of a stream is increased by?
headward erosion, progressive meander development, and delta building
headward erosion
upslope stream erosion resulting in an increase in the length of the valleys until the streams reach the divide
perennial stream
stream which flows only during part of the year
baseflow
supplies water to the stream when the water table is high but the channel becomes dry when the water table is lower than the stream channel
ephemeral stream
stream which flows in response to rainfall; typically in arid and semi-arid regions
meandering streams
river confined to a single channel and channels are sinuous
pools
at low flow these are deep areas characterized by relatively slow water flow (produced by scour at high flow)
riffles
at low flow these are shallow areas recognized by relatively fast water flow (produced by depostional processes at high water flow)
well developed pool-riffle sequences are repeated approximately?
5 to 7 times the channel width
streams with well developed pools and riffles tend to have considerable?
gravel in the stream bed and relatively low slope
streams with finer materials or steep slopes tend to lack?
regularly spaced pools and riffles
pools and riffles are also developed in?
bedrock channels
characteristic features of meandering streams:
1. river confined to a single channel and channels
2. bank composed of tough material
3. rivers have high suspended load-silt, clay
4. channels can be shallow or deep
Braided streams characterisitic features:
1. stream consists of many channels seperated by numerous bars and islands
2. channels are typically challow
3. channel and bank materials are loose, unconsolidated; these include sand and gravel
4. streams are characteristically bed load
influent stream
stream which flows above water table and adds water to the ground
effluent stream
stream fed by groundwater
Where are effluent streams found?
typically in humid, temperate regions (streams tend to be perennial)
where are influent streams found?
typically in arid regions (streams are intermittent or ephemeral)
upstream floods
occur in upper parts of drainage areas and are generally produced by intense rainfall of short duration over a relatively small area
downstream floods
cover wide area and are usually produced by storms of long duration that saturate soil and produce increased runoff
sheet flooding
occurs in areas of very low to flat topography and few streams; flood waters run off the land surface in the downslope direction