WSP07358

• File Number: 7630.125
• Description: Wild and Scenic - Colorado Wilderness Act - 1991
• State: CO
• Basin: Statewide
• Date: 7/1/1991
• Author: Hill and Platts
• Title: Ecological and Geomorphological Concepts for Instream and Out-of-Channel Flow Requirements - Excerpt From Rivers - Volume 2 Number 3
• Water Supply Pro - Doc Type: Report/Study

,
, 002833
8
7 .
VAllEY MAINTENANCE FLOW 2000
1 .
6 MAXIMUM RIPARIAN FLOW ;;
E MINIMUM RIPAR"N FLOW. -
1600 M
5 .s
Z
0 w
f= 4 1200 ~
< a:
> <
W 3 I
..J 800 ()
W ({J
2 15
400
0
0 115 125 135 145 155 165 175 185 195
DISTANCE (m)

FIGURE 3. Estim..ted HEC~Z model me.asurements on .. cross section of S..lmon River at Whitebird,
Idaho.

investigations have focused on local con.
ditions and have not been tested on a re-
gional basis,
The HEC-2 method can be used to esti-
mate effects of flow changes on channels
by predicting those velocities that disrupt
bed armor and fines from gravel beds. We
use HEC-2, however, to identify those aut-
of-channel flows that influence and main-
tain riparian and valley-forming processes.
As shown in Figure 3 for the Whitebird
site, HEC-2 predicts water surface at any
given elevation. The upper and lower el-

2500

evations of riparian habitat and the valley
is measured and HEC-2 used to determine
the discharge needed to reach those ele-
vations, HEC-2 transects can be simple ex-
tensions of IFIM transects and, therefore,
the required field effort for this model is
very minimal.
Floodplain maintenance is dependent
upon flooding at selected intervals if flood-
plain functions and vegetation are to be
maintained (junk et aL 1989). As shown in
Figure 4, these flows occur at the peak of
the hydrograph for the Whitebird site and

2000
;; 025
M 010
.s 1500 05
UJ
~ FISHERIES 0
a: RIPARIAN 0
< 1000
I
()
({J
15 500

M J J A
MONTH
FIGURE 4. Fisheries .and riparian-flood flow curves for S.lmon River.at Whilebird, Id..ho.

o
J

"

M

A

I~I 206

S

o

N

D

Rivers. Volume 2, Number 3

July 1991