Exam #1 Flashcards
Drainage density
Reflects spacing of stream channels
D= length of channel (km) / basin area (km2)
Stream order and 3 methods
Way to describe stream size
Horton, shreve, strahler
Horton stream order
Looks at entire stream length
Strahler stream order
Just stream reach
Shreve stream order
Just stream reach but additive
Basin magnitude (m)
Of first order streams in a basin
Magnitude=shreve stream order
Ruggedness Number
Drainage density x relief
Relief = max elev - min elev
Reynolds’s number
Describes properties of flow
Re <_ 500 = laminar
Re>_ 2000 = turbulent
Ke = 500-2000 = transition from L to T
Reynolds’s Number equation
Re=vle/u
V=flow velocity
L= length→ a/Pw
e= density of water
u= viscosity of water
Hydraulic radius
Ratio that describes how efficient water flow is
Rh= A/ pw
A-cross sectional area
Pw- wetted perimeter
Froude Number
Ratio of water velocity (v) and surface wave propagation velocity (vw)
→ measures how erosive flow is
Fr= v / vw =v/ square root (gh)
V-velocity of water
G-accel of gravity
H-height of water column
Supercritical
V> vw → fr> 1
Shallower flow, more erosive energy
Critical flow
V= vw → fr =1
Ripple wave moving upstream would be stationary
Subcritical flow
V< vw → fr <1
Tranquil, deeper flow.. Little erosive energy
Q-H relationship for critical flow @dip
Q = WcHcVc
Q → river discharge
Wc →width
Hc →height
Vc → square root ( gh)
Water flow over a spillway
Q=Wc (square root of 8/27 g)H^ 3/2
Wc = width of water@top of dam
H= height of water just above dam
Q=v2WcH2
V2= velocity@ dip
H2=height of water at dip
Weirs
Man-made structure designed to force flow to become critical so Q can be calculated
Two main types of weirs
Rectangular→ flow through rectangular opening
Q = CWcH^ 3/2
V-notch → flow through v, more accurate
Q=ctan(0/2)H^5/2
Major water reservoirs
→ lakes/streams/river/ponds
→glaciers (ice)
→aquifers:ground water
→ atmosphere
→ soils
Hydrology
Mainly surface water concerned w/origin, circulation, distribution, properties of water on earth
Hydrography
Stream discharge (Q) over time
Infiltration capacity
Rate @ which water can be absorbed into ground
IC>P= No OF
IC<P=OF
Saturated overland flow
Antecedent moisture
Ground already saturated
Make things flashier
Subsurface storm flow
Moves through uncomplicated upper layer of soil/regolith
Annular
Structural domes + basins
Radial
Volcano, domes
What controls drainage patterns
Variable weathering by bedrock
Tectonics
Volcanism
Fractures, jointing
Slopes
Drainage density
Network of progressively larger channels that drain water from an area bounded by drainage divides
Watershed
“Catchment”
Area of land where water collects and drains through an outlet
Stage
Height above reference point
Staff gauge
Scale placed in water
Water balance
Way to track movement of water within and between a certain reservoir
In= out + s/t
Flowing water
Moving
Streams, runoff, rivers
Stagnant water
Lakes, ponds, wetland
Storage
Laminar flow
Flow that happens in thin, smooth, parallel layers with no disturbance
Turbulent flow
Velocity and direction of water particles vary erratically at any given point
Runoff/ Horton overland flow
Water flowing over ground surface directly into stream channel
Occurs where there is a barrier to infiltration
Creates flashy flows
Evapotranspiration
Vegetation uses water through root system
Excess water lost by evaporation directly from plant
Interception
Vegetation captures precipitation
Never reaches ground
Rate of 10-50 % of precip
Conformal
Mix of patterns
Multibasinal
Hummocky
Smile-like shapes
Rectangular
Joints @right angles
Trellis
Dipping or folding
Parallel
Moderate to steep slopes
Dendritic
Tree-like
Laser beams
Mounted on bridge or other overhead structure
Linked to data recorder
Laser beams
Mounted on bridge or other overhead structure
Linked to data recorder
Float recorder
Float dropped into stilling well and level is recorded
Analog or digital
Water needs to be relatively calm
Pressure transducer
Measures atmospheric pressure just above water level and water pressure below water surface to get depth change
May use stilling well
Stilling well
Well directly connected to stream channel
Good for measurements because effects of turbulence or flow variations are limited
Float
how long it takes for an object to move down channel at known distance
V =(0.65vfloat)
Thalweg
Fastest part of stream channel
Flow meter
Electronic device with impeller that is submerged to a certain depth
Measures total depth and take velocity from average point
Accoustic Doppler current profiler
Sonar technology that records velocity at different depths
Velocity profile
Ave. velocity approximated at 60% of water depth or 40% of water height
V=(V0.2h +2V0.4h +V0.8h)/4
Velocity area method
Cross section of a stream channel divided into sections and are added together
