FLOOD03746

• County: Boulder
• Basin: South Platte
• Title: Human Stability in a High Flood Hazard Zone
• Date: 8/1/1989
• Prepared For: CWCB
• Prepared By: David Love & Associates
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Human Stability in a High Flood Hazard Zone

from Eq, 2 is closely aligned to the flume test results for
the 117.5Ib monolith.
The results of the monolith analysis are considered
valuable as they represent an extrapolation scenario for
the young and aged that could not be tested in this
study" Although the analysis is very conservative, it
provides a starting point for future work,

Human Subjects

Twenty human subjects were prepared and tested in
the experimental program. Each subject was tested un-
til the individual indicated a loss of stability or maneu-
verability in the flow. Since each human subject had to
determine at what point they lost their maneuverability
in the flow, there exists a potentially wide range of
product numbers that portray subject instability.
The product numbers at instability of each subject
for each test condition is presented in Table 2 for the
0,005 channel slope and Table 3 for the 0,015 channel
slope. Product numbers at subject instability ranged
from 7.56 for subject 2 (124.5 Ibs) to 22.84 for subject 6
(201lbs).
It is evident that the product number range at
instability of a human subject weighing 124.5 Ibs (7,56-
15,18) is significantly greater than the range of product
numbers at toppling for the monolith (2,95-4.2). The
human subjects possess the innate skill to compensate
for varying flow conditions and bed slope by adjusting

body stance and body position. Figure 4 illustrates the
upright position of a 1611b subject in a flow with prod-
uct number of approximately 9, As the flow increases,
the subject tends to lean into the flow using arms and
hands to maintain balance as indicated in Figure 5
where the product number is approximately 14. When
the subject approached instability, the subject leaned
into the flow in an exaggerated manner. Periodically,
the subject shifted his/her weight seemingly
involuntarily to resist the force of the flood flow.
In an attempt to provide a means to quantitatively
predict the point of instability of the human subject, an
empirical analysis was conducted to relate the product
number to weight and height of the subject. A semi,log-
arithmic representation was formulated as shown in
Figure ~ 6 relating the square root of the product num-
bers from Table 2 and Table 3 to the product of the ap-
propriate subject weight (Ib) and height (inches). A lin-
ear regression, r" = 0.48, was performed yielding the
expression

P.N. = [exp[0,222(wt x htllOOO) + 1.088]) (5)

where P,N. is the product number, wt is subject weight
in pounds, and ht is the subject height in inches.
Equation 5 provides a numerical means of defining the
point of instability of a human subject in flood flow.
Stability was not found to be a function of surface type
for the surfaces tested in this study.

Figure 4. Human Subject in Flume, P.N. - 9.

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