Streambed level Structures

Streambed Level Structures

The five types of At-Stream-Bed Structure External Energy Dissipators are available in the program:

• Colorado State University (CSU) Rigid Boundary Basin

• Riprap Basin and Apron

• Contra Costa Basin

• Hook Basin

• USBR Type VI Impact Basin

Colorado State University (CSU) Rigid Boundary Basin

Colorado State University (CSU) Rigid Boundary Basin

No input variables are required for this calculation; however, one design is selected by the user.

All possible designs for CSU Rigid Boundary Basins are calculated for the given culvert and flow. Designs which do not dissipate sufficient energy are discarded. The criteria of the remaining designs are numbered and displayed one at a time.

Designs are calculated and displayed in order of increasing width, increasing number of element rows, and increasing element height. As a result, smaller, less expensive designs are presented first.

The following figures show a Colorado State University (CSU) Rigid Boundary Basin

Colorado State University (CSU) Rigid Boundary Basin 101

Variables from the figure

• W -- Culvert width at culvert outlet

• W -- Element width which is equal to element spacing0

• h -- Roughness element height1

Variables from the figure

• V -- Velocity at the culvert outlet

• V -- Approach velocity at two culvert widths downstream of the culvert outlet0

• V -- Exit velocity, just downstream of the last row of roughness elementsA

• y -- Depth at the culvert outletB

• y -- Approach depth at two culvert widths downstream of the culvert outlet0

• y -- Depth at exitA

• W -- Culvert width at the culvert outletB

• L -- Total basin length0 B

• L -- Longitudinal spacing between rows of elements

Variables from the figure

• W -- Width of basin

• W -- Culvert width at the culvert outletB

• L -- Longitudinal spacing between rows of elements0

• N -- Row number

Riprap Basin and Apron 103

Riprap Basin and Apron

Riprap Basin and Apron

The input variables required for this calculation is the following:

• Condition to compute Basin Outlet Velocity -- The user can select 'Best Fit Curve' or 'Envelope Curve'. The user should choose 'Best Fit Curve' if the flow downstream of the basin is believed to be supercritical. If the flow downstream is believed to be subcritical, the user should choose 'Envelope Curve'.

• D50 of the Riprap Mixture -- Mean diameter (by weight) of the riprap to be used.

• DMax of the Riprap Mixture -- Maximum diameter (by weight) of the riprap to be used.

The design criteria for this basin was based on model runs in which D50/YE ranged from 0.1 to 0.7; values outside this range are rejected by the program.

The following figures show riprap basins and aprons.

Variables from the figure

• h -- Dissipator pool depth

• W -- Culvert widthS 0

• TW -- Tailwater depth

• y -- Equivalent brink (outlet) depth

• d -- Median rock size by weighte

• d50

max-- Max rock size by weight

Contra Costa Basin

Contra Costa Basin

The input variables required for this calculation is the following:

• Baffle Block Height Ratio -- The ratio of the baffle block height to baffle block distance from the culvert.

• End Sill Height to Maximum Depth Ratio -- ratio to determine the end sill height from the maximum depth.

• Basin Width -- The channel width is recommended for the basin width.

The following figures show the design of a Contra Costa basin.

Variables from the figure

Contra Costa Basin 105

• D -- Diameter of culvert

• y -- Outlet depth

• y -- Approximate maximum water surface depth0

• y -- Basin exit velocity2

• V -- Outlet velocity3

• V -- Exit velocity0

• h -- Height of small baffle2

• h -- Height of large baffle1

• h -- Height of end sill2

• L -- Length from culvert exit to large baffle3

• L -- Length from large baffle to end sill2

• L -- Basin length3 B

Hook Basin

Hook Basin

The input variables required for this calculation is the following:

• Shape of Dissipator -- The user can select 'Warped Wingwalls' or 'Trapezoidal'. See illustrations below for examples.

• Flare Angle (Warped Wingwalls only)-- Flare angle per side of the basin.

• Ratio of Length to A-hooks over Total Basin Length (Warped Wingwalls only)-- Distance from culvert exit to first row of hooks (A-HOOKS) divided by the total length of the basin.

• Ratio of Width to A-hooks over Total Basin Length (Warped Wingwalls only)-- Distance between hooks in the first row divided by the basin width at the first row.

• Ratio of Length to B-Hooks over Total Basin Length (Warped Wingwalls only)-- Distance from culvert exit to second row of hooks (B-HOOKS) divided by the total length of the basin.

• Width for the Downstream End of the Basin (Warped Wingwalls only)

• Basin Side Slope (Trapezoidal shape only) -- The user can select either '1.5 : 1' or '2 : 1'.

• Basin Bottom Width (Trapezoidal shape only)

The next two figures show a hook basin with warped wingwalls:

Hook Basin 106

Variables from the figure

• W -- Outlet width

• W -- Width at first hooks0

• W -- Distance between first hooks (row A)1

• W -- lateral spacing between A and B hook2

• W -- Width of hooks3

• W -- Width of slot in end sill4

• W -- approximately channel width5

• h -- Height of end sill6

• h -- Height to top of end sill4

• h -- Height to top of warped wingwall5

• y -- Equivalent depth6

• L -- Distance to first hookse

• L -- Distance to second hooks (row B)1

• L -- Basin length2 B

Variables from the figure

• ß -- Angle of radius

• r -- radius

• h -- height to center of radius

• h -- Height to point1

• h -- Height to top of radius2

• y -- Equivalent depth3 e

The next two figures show a hook basin with a uniform uniform trapezoidal channel:

Variables from the figure

• W -- Outlet width

• W -- Width at first hooks0

• W -- Distance between first hooks (row A)1

• W -- lateral spacing between A and B hook2

• W -- Width of hooks3

• W -- Width of slot in end sill4

• W -- approximately channel width5

• h -- Height of end sillB

• h -- Height to top of end sill4

• h -- Height to top of warped wingwall5

• y -- Equivalent depth6

• L -- Distance to first hookse

• L -- Distance to second hooks (row B)1

• L -- Basin length2 B

Variables from the figure

• ß -- Angle of radius

• r -- radius

• h -- height to center of radius

• h -- Height to point1

• h -- Height to top of radius2 3

USBR Type VI Impact Basin 109

USBR Type VI Impact Basin

USBR Type VI Impact Basin

No input variables are required for this calculation.

The following figures show a USBR Type VI impact basin.

Variables from the figure

• W -- Required basin width

• W -- Geometry design variableB

• h through h1

1 5-- Geometry design variable

• t through t

1 5-- Geometry design variable

• L and L

1 2-- Geometry design variable

• L -- Length of the Basin

In document Manual Hy8 Traduc (Page 141-151)