Hydraulics for Hydrographers Channel Dynamics and Shift Corrections AQUARIUS Time-Series Software™ Aquatic Informatics Inc

Hydraulics for HydrographersChannel Dynamics and Shift Corrections

AQUARIUS Time-Series Software™Aquatic Informatics Inc.

www.aquaticinformatics.com | 2

Concepts, terms and definitionsFluvial ProcessesHydraulic GeometryEcoHydraulicsShift Corrections

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Mechanics of transportSolutionFlotationSuspensionSaltationTraction

Fluvial Processes

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.

Suspended Load


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 landscapeUnderstanding the landscape upstream of your gauge can help in interpreting Shift Corrections

Revised Universal Soil Loss Equation


CPLSKRA

Where: Vs is settling velocity; ρp is density of the particle; ρf is density of the fluid; g is gravity; r is radius of particle; and m is viscosity

Stoke’s Law for settling velocity of supended particles


9

)(2 2grV fps

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

Bed Load: Saltation and Traction


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 velocityTherefore a small increase in velocity can have a large increase in the size of particle that can be moved

Sixth power law


63 kvr

The steep gradient of velocity near the stream bed lowers the pressure on the top of particles resulting in hydraulic liftThe 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

Hydraulic lift and the critical tractive force


gdsFt

Erosion, transport and deposition


0.001 0.01 0.1 1 10 1000.001

0.01

0.1

1

10

Diameter (mm)

velo

city

(m/s

)

Erosion

Deposition

Transport

Fluvial Landforms


Dynamic equilibrium


0 10 20 30 40 50 60 70 80 90 1000

500

1000

1500

2000

% of basin area

elev

ation

(m)

hypsometric integral = 0.45

Hydraulic Geometry


baQwcQfd

mkQv

WDVAVQ

0.1 kca

0.1 mfb

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’

Hydraulic Geometry


Hydraulic geometry


100 1000 10000D ischarge (m 3/s)

10

100

1000

Wid

th (

m)

1

10

100

De

pth

(m

)

0 .1

1

10

Ve

loci

ty (

m/s

)

103.0

303.0

595.0

542.53

781.0

024.0

Qw

Qd

Qv

Hydraulic Geometry


10/3/54 8/28/76 7/24/98D ischarge (m 3/s)

-0 .4

-0.2

0

0.2

0.4

Ve

loci

ty R

esi

du

als

(m

/s)

-1 .0

0.0

1.0

De

pth

Re

sid

ua

ls (

m)

-20

-10

0

10

20

Wid

th R

esi

du

als

(m

)

Beavers=leaky weirs

VegetationBiofilmsSubmergentEmergentRiparian and LWD

EcoHydraulics


Stage data are more indicative of reach storage than of dischargeBeavers 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)

EcoHydraulics


dt

SQQ io

Simplistic Hydraulic solutions are invalidHydrologic 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)

Beaver Dams


The effects of river ice are discussed in the lesson “River Ice Processes and Dynamics”

River ice


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.

Biofilms


Note: Rock Snot (Didymosphenia geminata) is transferred from watershed to watershed on waders – clean your waders between measurements if you don’t want to be responsible for its spread

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 and the Head-Area relation.Use a time-based knee-bend shift to the left

Submergent Lotic 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.

Emergent Lentic Vegetation


Riparian vegetation competes for sunlight in forests by growing out over the stream channelOverhanging 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

Riparian vegetation - overhanging


Sweepers alter the wetted perimeter, PZH, and the Head-Area relation.

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

Riparian Vegetation – floating LWD


Riparian Vegetation – spanning LWD


Stream bed

Log spanning streambanks

Normal rating curve

Abstraction and obstruction of flow

High water – critical flow

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

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)

Other types of channel dynamics


Natural River Channels are seldom static (Aggradation/Degradation/ Fill / Ice / Weed Growth)Even artificial controls are subject to shifts (debris / algae)

Rating Curve Shifts


Aggradation or degradation of the banks generally affects the exponent, which calls for a stage-based correction whereas aggradation or degradation of the bed primarily affects PZH, which usually indicates a time-based, stage-based correction

Fluvial dynamics

0.001 0.01 0.1 1 10 1000.001

0.01

0.1

1

10

Diameter (mm)

velo

city

(m/s

)

Transport


Can be developed in three waysTyping in shift points in the Shift ManagerAdjusting points in the Shift DiagramOn the rating curve zoom plots

Shift dates can be specified inThe Shift ManagerThe Time Series Pane (Shift Period Bars)

Shifts in AQUARIUS


Sometimes Shifts are not staticWeed growth, fill, and scour can take place graduallyAQUARIUS lets you prorate a shift by leaving the ‘end date’ unspecified.An unspecified ‘end date’ shift will pro-rate into the next shift

Shifting by Time


In the next lesson: ‘River Ice Processes and Dynamics’ we will look at hydraulic and hydrologic approaches to estimating winter streamflow.

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Recommended, on-line, self-guided, learning resources

USGS GRSAT traininghttp://wwwrcamnl.wr.usgs.gov/sws/SWTraining/Index.htm

World Hydrological Cycle Observing System (WHYCOS) training materialhttp://www.whycos.org/rubrique.php3?id_rubrique=65#hydrom

University of Idahohttp://www.agls.uidaho.edu/bae450/lessons.htm

Humboldt Collegehttp://gallatin.humboldt.edu/~brad/nws/lesson1.html

Comet Training – need to register – no costhttp://www.meted.ucar.edu/hydro/basic/Routing/print_version/05-stage_discharge.htm#11

http://wwwrcamnl.wr.usgs.gov/sws/SWTraining/Index.htm

http://www.whycos.org/rubrique.php3?id_rubrique=65#hydrom

http://www.agls.uidaho.edu/bae450/lessons.htm

http://gallatin.humboldt.edu/~brad/nws/lesson1.html

http://www.meted.ucar.edu/hydro/basic/Routing/print_version/05-stage_discharge.htm#11

http://www.meted.ucar.edu/hydro/basic/Routing/print_version/05-stage_discharge.htm#11


Thank you from the AI TeamWe hope that you enjoy AQUARIUS!

Documents

Hydraulics for Hydrographers Channel Dynamics and Shift Corrections AQUARIUS Time-Series Software™ Aquatic Informatics Inc