Canals USBR Flashcards
Trapezoidal is the most accepted shape for earthern canals
T or F?
True
Side slopes of 3:2 for smaller canals and laterals and 4:2 for larger canals is generally adequate for most earth materials and should be considered when determining the side slopes of canals
T or F?
True
3.0 fps for smaller canals up to 1.5 fps for larger are the range of permissible velocities considered for sizing a canal water section
T or F?
False
What considerations must be made when canal construction is to utilize “cut and fit” methods?
- The water prism should be kept a safe distance into the natural ground
- Generally the ground water surface above the downhill cut take should not exceed approximately one-fourth the water depth
- On steep sidehills the entire water prism should be entirely in the natural ground for safe consideration
- All above
All above
Steel flumes are seldom used today due to High maintenance costs
T or F?
True
Alone uphill terrain concrete bench flumes are most commonly used
T or F?
False
What shape of flume gives the maximum velocity for a given area?
- One that has a bottom width 4 times the depth of the water depth
- One that has a bottom width 2 times the depth of the water depth
- One that has a bottom width 3 times the depth of the water depth
- None above
One that has the bottom width 2 times the water depth
Encountered falling rock and debris are ideal conditions to make precast concrete pressure pipe for flume service
T or F?
True
Buried precast concrete pipe and monolithic concrete pipe are considered common types of construction for siphon service
T or F?
True
Why is concrete pipe predominantly used for canal siphons?
- Hydrostatic heads encountered are generally less than 150 ft
- Bridges supporting canal sections across drainage channels, over highways and railroads, are generally more expensive
- Sizes from 12 to 96 inches are available in most localities
- All above
All Above
Monolithic construction is generally considered for siphons smaller than 96 inches in diameter
T or F?
False
Factors that may dictate construction of elevated steel pipe siphons could be where costly rock excavation is encountered and limited space for handling river flows during construction
T or F?
True
What essential design features, in addition to the pipe itself, must be considered for inverted siphons?
- Inlet and outlet transitions
- Blowoff structures
- Non pressured lines
- Both A and B
Both A and B
Inlet and outlet transitions serve for the purpose of maximizing head loss and erosion damage
T or F?
False
A pump type, gravity pump, and pressure turnout type, are all considered blowoff structures
T or F?
True
When feasible, blowoffs should be located at the low points of siphon where water is drained into natural drainage channels
T or F?
True
To dislodge sediment and debris that may become packed in the discharge line immediately upstream of the blowoff valve is the purpose of the high velocity jet utilized in some gravity blowoffs
T or F?
True
To convey water over relatively steep slopes to lower grades and water surfaces in canals or laterals is the purpose of chute (drop)
T or F?
True
What purpose do the controlled notch or stoplogs serve in the inlet transitions of drops and chutes?
- Prevents sedimentation from buildup
- Prevents drawdown at the entrance that would cause erosion of canal
- Prevents flooding
- None above
Prevents drawdown at the entrance that would cause erosion of canal
If maximum velocities are more than 3.5 fps, an outlet transition is generally not necessary
T or F?
False
By providing a depressed (submerged) section of pipe ahead of the outlet transitions, superficial velocities are dissipated in pipe drops
T or F?
True
Water Hammer is a reason why open type stilling pools or impact basins utilitze outlet transitions for pipe chutes
T or F?
True
What is the preferred shape of a monolithic reinforced concrete chute?
- circle
- triangle
- rectangular
- missing
rectangular
Besides stoplogs, siphons are devices used to control water levels at the inlet of monolithic reinforced concrete drops and chutes
T or F?
False
The energy dissipated by the blocks constructed along the floor of the chute is when a conventional stilling pool is utilized in the baffle apron drop.
T or F?
False
Cross drainage structures serve the purpose to protect canals from damage from algae
T or F?
False
Relative capacity of canal with respect to drainage flows and canal water surface with respect to natural ground surface dictates the need of cross drainage
T or F?
True
Where the canal is carried across a natural drainage channel upon an embankment, culverts are used for cross drainage
T or F?
True
For large canals, what storm frequency is used to develop culvert size?
- 500 year storm frequency
- 100 year storm frequency
- missing
- missing
100 year storm frequency
The purpose that pipe collars serve in culvert constructions is to prevent water seepage in discharge line
T or F?
False
What conditions dictate the use of an overchute?
- Where the waster surface of the canal is below the natural water surface
- Where loss in grade in the canal is not permissible
- Are generally found economical on large canals where the drainage flows are small by comparison to canal flows
- All above
All above
When the amount of drainage water is large by comparison to the canal is what make drainage inlets acceptable
T or F?
False
Two important factors that dictate the placement of a drainage inlet intake are that the intake must be located below the maximum water surface elevation and at the natural ground level surface
T or F?
False
Flow control and flow measurement are considerations for regulating structures
T or F?
True
What devices are generally employed for flow control?
- Pumps
- Slide gates
- Lift gates
- Generators
- Radial steel gates
- Slide gates
- Lift gates
- Radial steel gates
Parshall flume and cipolleti weir are two mearuring structures for turnouts
T or F?
True
Wasteways serve the purpose so that they are utilized to dispose excess water from canals and to safely empty canals in case of canal break or emergencies.
T or F?
True
A sudden decrease in discharge when the siphon primes is detrimental to the wasteway channel and would be considered in disadvantage of siphon spillways.
T or F?
False
Overflow spillway without gate control is the type of wasteway construction that is preferred
T or F?
False
Checks serve the purpose to control the flow of water when at partial capacity
T or F?
True
Two general types of checks used in small canals are those using flashboards for regulation, or a combination of gates and flashboards for regulation.
T or F?
True
Radial gate checks of the California Aqueduct always employ overflow weirs
T or F?
False
