7934

• UCREFRP Catalog Number: 7934
• Author: Hyra, R.
• Title: Methods of Assessing Instream Flows for Recreation.
• USFW Year: 1978.
• USFW - Doc Type: Instream Flow Information Paper No. 6,
• Copyright Material: NO

Table 3. Total surface area of stream and (weighted
usable surface area) for a hypothetical
recreation activity in square feet.
Depth ft Velocity in feet per second and probability-of-use
d
an
(Probability- <0.5 0.5-1,0 1.0-1.5 >1.5 Total
of-use) (1.0) (0.8) (0.4) (0)
<1 500 400 100 0 1,000
(o) (o) (o) (o) (o) (a)
1-2 600 700 800 300 2,400
{0.3) (180) (168) (96) (0) (444)
2-3 100 300 500 100 1,000
{0.8) (80) (192) (160) (0) (432)
>3 0 0 100 D 100
(1.0) (0) (0) (40) (0) (40)
Totals 1,200 1,400 1,500 400 4,500
(260) (360) (296) (0) (916)
A separate matrix is required for each recreation activity being
considered. A separate matrix is also developed for each of a number of
different flows and a different weighted usable surface area is calcu-
lated for each flow. Comparison of the matrices provides information on
the "best flow" or shows the change in weighted usable surface area due
to a change in flow.
RECREATION CRITERIA FOR THE INCREMENTAL METHOD
Recreation activity definitions and a discussion of criteria are
presented below.
Minimum and Maximum Criteria
Criteria, as discussed in this section, refer to the parameters of
depth and velocity, and deal with the minimum and maximum values. The
assumption is made that the recreation activity in question cannot be
engaged in outside of the range described by the minimum and maximum
values. Optimum values are determined in a somewhat different manner
and will be discussed later. Minimum and maximum criteria are of two
major types: (1) physical criteria and (2) safety criteria. Regarding
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