FLOOD05499

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Urban Storm Runoff Inlet Hydrograph Study - Volume 5
• Date: 5/1/1975
• Prepared By: Cheng-lung Chen
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

ing, the inaccuracy of using Eq, 33 before and after
ponding manifested itself on the infiltration decay
curve in the form of oscillation, as will be shown later
in this report.

Soil properties V!.O) and K(O) relationships

The physical properties of soil such as the V!.O)
and K(O) relationships are required in the solution of
the numerical model, Eqs, 20 through 24, In the
present study, sandy clay loam at the Hullinger Farm
near Vernal, Utah, was selected and tested, The 1/1(0)
and K(O) relationships as determined by Nimah and
Hanks (1973) were used, The moisture diffusivity,
0(9), was determined by using its definition

D(a) - K(O) ~
dO

For illustration, these soil property relationships are
shown in Figures 3 through 5 and also tabulated in
Table 3, It can readily be seen from Figure 5 and

, , , . , ' . ' .(34)

.106

.105

e
u

4
-'0

...

:!
;;
.
8-
~
"
~
'a
.
u

.103

s

_IOZ

-10

o

0.4

SoU mobture content .. .

Figure 3, Functional relationship between soil cap-
illary potential (1/1) and soil moisture ""....
tent (9) for VemaI saudy day 108lI'l,

Table 3 that the shape of the 0(9) relationship is
quite irregular. ]n the modeling, it is thus much easier
and more reliable to use the 1/1 ( 9) relationship than
the 0(0) relationship,

The aforementioned procedures of computa-
tion and the functional relationships of soil properties
for Vernal sandy clay loam are programmed in
Fortran V and executed in the UNIVAC 1108
computer for validation of the present rmite-
difference model.

Computer Results

Many computer runs were conducted for the
purpose of examining the validity and performance
characteristics of the present numerical model. Com-
puter results for a typical run are shown in Figure 6,
in which the 9 -profiles, the 1/I-distributions in the
saturated zone, and the ponding depth variations are
all plotted on ordinary scale, but the infiltration

10

10.1

0.5

lO.Z
" IO.l
~
E
"
~ 10.4
~
:~ 10.5
,
~
c
c
u
,~
.. 10.6
.
"
~
~
'"
10.7
10.8
10.9
0 0,1 0, . 0,3 0,4 0,5

SOU mol.tore content.. .

Figure 4, FUDCtional relationship between hydraulic
conductivity (K) and soil moisture content
(9) for Vernal sandy clay loam,

22