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. Suspended Load • 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. Stoke’s Law for settling velocity of supended particles • 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

7. Bed Load: Saltation and Traction • 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 (Didymospheniageminata) is transferred from watershed to watershed on waders – clean your waders between measurements if you don’t want to be responsible for its spread

22. SubmergentLotic 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 and the Head-Area relation. • 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 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

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 (Aggradation/Degradation/ Fill / Ice / Weed Growth) • Even artificial controls are subject to shifts (debris / algae)

29. Fluvial dynamics 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

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 gradually • 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/sws/SWTraining/Index.htm World Hydrological Cycle Observing System (WHYCOS) training material http://www.whycos.org/rubrique.php3?id_rubrique=65#hydrom University of Idaho http://www.agls.uidaho.edu/bae450/lessons.htm Humboldt College http://gallatin.humboldt.edu/~brad/nws/lesson1.html Comet Training – need to register – no cost http://www.meted.ucar.edu/hydro/basic/Routing/print_version/05-stage_discharge.htm#11

34. Thank you from the AI Team We hope that you enjoy AQUARIUS!