SPILLWAY RATINGS and STABILITY DESIGN PROCEDURES __________________________ SITES 2005 INTEGRATED DEVELOPMENT ENVIRONMENT for WATER RESOURCE SITE ANALYSIS

OBJECTIVE Provide understanding of: Principal spillway rating Auxiliary spillway rating Permissible velocity approach Allowable stress approach Cover discontinuities

The first elevation entry in the table must correspond to the spillway crest elevation. The first discharge entry must be zero, and the subsequent discharge entries must increase with increasing elevation.

Inlet Conduit

EXAMPLE HELP

the rating for the auxiliary spillway may be entered at the structure table

AUXILIARY SPILLWAY RATING FEATURES VARIABLE FLOW RESISTANCE VARIABLE FLOW RESISTANCE (by reach) MIXED VEGETAL AND NON-VEGETAL MIXED VEGETAL AND NON-VEGETAL flow resistance SEEKS HYDRAULIC CONTROL SECTION SEEKS HYDRAULIC CONTROL SECTION

Auxiliary Spillway Profile Inlet Natural Ground Constructed Inlet Channel Constructed Exit Channel Exit Natural Ground Tie Sta.

X SPILLWAY PROFILE Avoid short steep slopes between mild slopes! The program identifies the hydraulic control as the upstream end of the first reach downstream of the crest that flows supercritical at the discharge in question. Reach length is not checked. Therefore, short steep reaches that may be submerged by mild slope reaches downstream may cause improper rating.

C I = 5.6 n = 0.04

AUXILIARY SPILLWAY STABILITY ANALYSIS SITES

SITES TECHNOLOGY OPTIONS PERMISSIBLE VELOCITY PERMISSIBLE VELOCITY ALLOWABLE STRESS ALLOWABLE STRESS COMPUTATIONAL OPTIONS ENTER BED WIDTH ENTER BED WIDTH - COMPUTE STRESS LEVEL ENTER ALLOWABLE STRESS LEVEL ENTER ALLOWABLE STRESS LEVEL - COMPUTE BED WIDTH

VEGETAL EROSION PROTECTION

PERMISSIBLE VELOCITY COVERSLOPE % EROSION RESISTANT EASILY ERODED Bermudagrass > Kentucky Bluegrass > Weeping Lovegrass (ft/s)

VEGETAL COVER FACTOR used to compute EFFECTIVE STRESS COVER COVER FACTOR Bermudagrass Kentucky Bluegrass Weeping Lovegrass CFCF

AH 667 TP 61 ORDINARY FIRM LOAM SILT LOAM SANDY LOAM EROSION RESISTANT EASILY ERODED FLOW DEPTH, ft AVERAGE VELOCITY, ft/s

MAINTENANCE CODE 1 - UNIFORM COVER OR SURFACE 2 - MINOR DISCONTINUITIES 3 - MAJOR DISCONTINUITIES

EFFECTIVE STRESS Maintenance code effect Maintenance code effect  e =  ds(1-C f ) (n s /n) 2 If MC=2, C f  0 If MC=3, Cf  0 and n  n s

AUXILIARY SPILLWAY STABILITY ANALYSIS SITES SUMMARY BASED ON PEAK OF SDH BASED ON PEAK OF SDH APPLIED TO EXIT CHANNEL APPLIED TO EXIT CHANNEL VELOCITY OR STRESS calculations VELOCITY OR STRESS calculations COMPUTE V,  e, or BED WIDTH COMPUTE V,  e, or BED WIDTH MAINTENANCE CODE for stress calculations MAINTENANCE CODE for stress calculations