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## Hydraulics for Hydrographers Channel Dynamics and Shift Corrections

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### Hydraulics for HydrographersChannel Dynamics and Shift Corrections. AQUARIUS Time-Series Software Aquatic Informatics Inc. – PowerPoint PPT presentation

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Title: Hydraulics for Hydrographers Channel Dynamics and Shift Corrections

1
Hydraulics for HydrographersChannel Dynamics and
Shift Corrections
AQUARIUS Time-Series Software Aquatic
Informatics Inc.
2
Preview
• Concepts, terms and definitions
• Fluvial Processes
• Hydraulic Geometry
• EcoHydraulics
• Shift Corrections

3
Fluvial Processes
• Mechanics of transport
• Solution
• Flotation
• Suspension
• Saltation
• Traction

4
• For a sediment particle to be held in suspension,
the settling velocity must be less than or equal
to the turbulent velocity
• As discharge increases, the suspended load
increases at a more rapid rate than the
discharge.
• The enhanced concentration is due to erosion of
the drainage basin, not of scouring of the
channel.

5
Revised Universal Soil Loss Equation
• Where A soil loss R is rainfall erosivity K
is soil erodibility LS is topography (length of
slope and slope) P is a conservative practices
factor and C is a cover factor
• Most sediment originates from the landscape
• Understanding the landscape upstream of your
gauge can help in interpreting Shift Corrections

6
Stokes Law for settling velocity of supended
particles
• Where Vs is settling velocity ?p is density of
the particle ?f is density of the fluid g is
gravity r is radius of particle and m is
viscosity

7
• Saltation refers to low extended trajectories of
sediment particles of particles with less mass
than the tractive force.
• Traction is the movement of larger particles by
rolling or sliding

8
Sixth power law
• The radius of the largest particle that can be
set in motion by a given velocity is
• Where r is radius k is a constant that includes
gravity and grain density and v is flow velocity
• Therefore a small increase in velocity can have a
large increase in the size of particle that can
be moved

9
Hydraulic lift and the critical tractive force
• The steep gradient of velocity near the stream
bed lowers the pressure on the top of particles
resulting in hydraulic lift
• The column of water supported by a particle
exerts as critical tractive force
• Where Ft is critical tractive force r is density
of water g is gravity d is depth of water and
s is the gradient of the stream

10
Erosion, transport and deposition
11
Fluvial Landforms
12
Dynamic equilibrium
13
Hydraulic Geometry
14
Hydraulic Geometry
• Channels with resistant bank-forming material
such as cohesive silts have large values for f
and low values for b
• Whereas channels with weak bank forming material
such as sand have low values for f and high
values for b

15
Hydraulic geometry
16
Hydraulic Geometry
17
EcoHydraulics
• Beavers
• leaky weirs
• Vegetation
• Biofilms
• Submergent
• Emergent
• Riparian and LWD

18
EcoHydraulics
• Stage data are more indicative of reach storage
than of discharge
• Beavers regulate flow to control water table
(e.g. To expand riparian zone) or to regulate
water level (e.g. For protection of lodge
entrance from predators)

19
Beaver Dams
• Simplistic Hydraulic solutions are invalid
• Hydrologic solutions include
• Estimation of flow from representative gauged
basins (e.g. using Empirical modeling toolbox)
• Interpolation between measurements with
adjustments for runoff processes (e.g. using
Data Correction Toolbox)
• Use of rainfall-runoff modeling (e.g. using
custom toolboxes)

20
River ice
• The effects of river ice are discussed in the
lesson River Ice Processes and Dynamics

21
Biofilms
• Biofilms are thin layers of algae that form under
favourable conditions
• They are slippery - affecting the coefficient
in the rating equation - use a time-based to the
right.
• If thick enough - the dominant effect may be on
PZH, which can be temporarily be handled with a
time-based shift to the left.

Note Rock Snot (Didymosphenia geminata) is
transferred from watershed to watershed on waders
dont want to be responsible for its spread
22
Submergent Lotic Vegetation
• Vegetation that does not break the water surface
affects both the PZH and the Head- Area relation
• Note that the effect varies with stage because
high velocities flatten the weeds. At low
velocities the weeds have a greater effect on PZH
• Use a time-based knee-bend shift to the left

23
Emergent Lentic Vegetation
• In addition to all the effects of submergent
vegetation Emergent vegetation (e.g. lily pads)
affect the wetted perimeter -fundamentally
altering the Hydraulic Radius upon which the
rating curve is based.
• Use a time-based, truss shift to the left.
• Knowing the timing of emergence is crucial.

24
Riparian vegetation - overhanging
• Riparian vegetation competes for sunlight in
forests by growing out over the stream channel
• Overhanging vegetation may only come in contact
with the water during high flows
• Overhanging vegetation affects wetted perimeter,
and will result in an abrupt stage change at time
of contact
• Use an upside down knee-bend shift to the left

25
Riparian Vegetation floating LWD
• Sweepers alter the wetted perimeter, PZH, and the
• Use a time-based shift correction because they
are floating - the effect is more or less uniform
with respect to stage.
• If the sweeper is nasty full of green branches
etc. it may not be possible to accurately
estimate discharge using simplistic hydraulic
assumptions in which case hydrologic methods may
be required

26
Riparian Vegetation spanning LWD
High water critical flow
Log spanning streambanks
Abstraction and obstruction of flow
Normal rating curve
Stream bed
Use a combination of the base rating curve at
low-water, hydrologic (coefficient and exponent
are unrelated to base rating curve) estimation
from first contact to submergence of the log and
a new rating curve at high water
27
Other types of channel dynamics
• Variable backwater
• Estuaries
• Confluences
• Anthropogenic effects - Shopping carts, bicycle
frames etc.
• Evaluate the hydraulic parameters affected and
shift according to the type (time-based if the
coefficient is affected stage-based if the
exponent is affected time-based, stage-based if
PZH is affected)

28
Rating Curve Shifts
• Natural River Channels are seldom static
Growth)
• Even artificial controls are subject to shifts
(debris / algae)

29
Fluvial dynamics
affects the exponent, which calls for a
degradation of the bed primarily affects PZH,
which usually indicates a time-based, stage-based
correction
30
Shifts in AQUARIUS
• Can be developed in three ways
• Typing in shift points in the Shift Manager
• Adjusting points in the Shift Diagram
• On the rating curve zoom plots
• Shift dates can be specified in
• The Shift Manager
• The Time Series Pane (Shift Period Bars)

31
Shifting by Time
• Sometimes Shifts are not static
• Weed growth, fill, and scour can take place
• AQUARIUS lets you prorate a shift by leaving the
end date unspecified.
• An unspecified end date shift will pro-rate
into the next shift

32
Preview
• In the next lesson River Ice Processes and
Dynamics we will look at hydraulic and
hydrologic approaches to estimating winter
streamflow.

33
Recommended, on-line, self-guided, learning
resources
USGS GRSAT training http//wwwrcamnl.wr.usgs.gov/s
ws/SWTraining/Index.htm World Hydrological
Cycle Observing System (WHYCOS) training
material http//www.whycos.org/rubrique.php3?id_ru
brique65hydrom University of
Idaho http//www.agls.uidaho.edu/bae450/lessons.ht
m Humboldt College http//gallatin.humboldt.edu/