FLOOD10307

• County: Statewide
• Basin: Statewide
• Title: Guidelines for Determining Flood Hazards on Alluvial Fans
• Date: 2/23/2000
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

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21

02/23/00

Table 2. Sediment transport formulas and classifications,

Sl'dlllll'nl 11,II1SIWI t IOllllULl
S
'^
'"
~ co
S '0 ... r::-
" '"
'^ 0 S '-0
'" ..J ~ '^ '" ~
'g' '0 ~ '" N ~ ..,
~ t-
u " '"
'0 :; ~ .. u
a:: 0 " ::; " '" ~ ~
;0- ..J u ~ ~ Iii ~
t- o. ~ ~ ~
00 .., '0 ~ 0 ... :I: :E '"
'" U 0 ~ ~ '-0
ell Vl ell ~ .0 ~ t- '"
~ U - ~
~ ~ " " Q" C ~ "
'"' ~ Oi! O2 ~ 'u 0 ~ ~ ~
~
0 '0 u u 'U ~ DO .s
'U 1;; "
ell ~ ~ '"' "" .. "" Iii
0 :E " " " " ~ " " '0
Criteria Grouping Q Vl iil iil ::; iil Q" '" ...: ;>- u
Approach Shear Stress y' y' '" y' y' y'
Power y' y' '"
Parametric '"
Load Component Bed Load y' y' '" '" '" '"
Suspended Load y'
Bed-Material Load y' '" '" '"

Despite the intense efforts expended in the development of these formulas, evaluation against field
data indicates that they commonly overpredict or underpredict sediment loads by orders of
magnitude of actual measured sediment transport rates, This discrepancy is likely a result of
imperfect knowledge of the physics of sediment transport and also of the extensive variability and
heterogeneity in hydrologic and geologic factors. For these reasons, no one formula is better than
the others. Selection of a sediment transport formula must be dictated by how well the conditions
of the problem at hand match the assumptions underlying the formula. Ifpossible, applicability of
the formula should be verified with site-specific field data.