FLOOD09983

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Mudflow A Two Dimensional Hyperconcentrated Sediment Flow-routing computer Model
• Date: 3/1/1989
• Prepared For: State of Colorado
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Educational/Technical/Reference Information

2,9

The yi e 1 d stress 1 y and the fl ui d vi seos i ty 1], are determi ned by the
empirical equations

B1Cv
"y = Cl1 e (2.18)

and

B2C
1] = Cl2 e v

(2.19)

where Cl and B have been defi ned by I aboratory experiment. Results of thi s
work are presented in Appendix B as Tabll~ B.1. The fluid viscosity and yield
stress are shown to be functions of the volumetric concentrat'ion. Varying the
concentration spatially and temporally in the model has a dramatic effect on the
flow parameters of discharge, velocity, and depth. The objective of modeling
hyperconcentrated sediment is to predict the general flow properties at specific
points on the alluvial fan and in the channel. The viscous friction slope term
can be approximated as follows:
For steady, shallow, uniform laminar now of depth (h) in a wide, open
channel of slope (So) with a smooth bed, the Darcy,Weisbach friction slope is
given by

.tr '

, hf l' V2
Sf = L = 8gh

(2.20)

where hf is the
friction slope.

l' is:

friction head loss,
For laminar, stable

L is the channel length, and Sf
flow, the Darcy,Weisbach friction

is the
factor

K
f =-
Re

(2.21)

where Re is the Reynolds and K is a vari ab I e factor dependable on slope,

channel roughness, and shape (K equals 24 for laminar flow on smooth bed).
Substitution of Equation 2,21 into Equation ,~.20 yields:

" _!ill.. 'L
;)1' - 8rm h2

(2.22)