FLOOD00867

• County: Statewide
• Title: Determination of Channel Change for Selected Streams, Maricopa County, Arizona
• Date: 1/1/2002
• Prepared For: Maricopa County Arizona
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

6,000
Cross-sectional area I-
5,000 w
w
u.
. . w
. a:
"
4.000 ::;)
0
VJ
:1;
<i.
Daily mean w
3,000 a:
discharge "
...J
. "
z
0
2,000 >=
'-'
w
VJ
en
VJ
0
1,000 a:
'-'

site. Several current-meter measurements of dis-
charge were made from the bridge, and these
measurements provide information about scour
and fill during high flows.

Gila River at Estrella Parkway, near
Goodyear, has a drainage area of 45,585 mi2. Only
large regional storms cause the river to flow
naturally because the river and most of its large
tributaries are regulated by dams. Sediment size in
the channel ranges from sand to cobbles. The
overbank area is an assortment of sand and gravel
deposits. Prolonged low flows are common at this
site because of wastewater-effluent discharge
upstream.

Bridge-measuring section.- Five current-
meter measurements of discharge were made
between January 6 and February 5, 1993. The
measurements ranged from 12,500 to 122,000 ft3/s
and were made during floodflow that reached a
peak discharge of 162,000 ft3/s at the gaging
station on January 9. Daily mean discharge and
cross-sectional area at the gaging station during
this period are shown in figure 9.

140.000
0
z
0
'-' 120.000
w
VJ
a:
w
0-
I- 100,000
w
w
u.
'-'
a; 80,000
::;)
'-'
:1;
ui
(!l 60,000
a:
"
J:
'-'
~ 40.000
0
z
"
w
:2
>- 20,000
...J
<(
0
0

Using the cross section of January 6, 1993, as
a basis of comparison, the cross section measured
on January 9 shows several feet of scour mostly in
the deepest part of the channel (fig. 10). The cross-
sectional area doubled in relation to the reference
elevation of 12 ft (figs. 9 and 10). The measure-
ment made after the peak shows a 12-percent de-
crease in cross-sectional area. Subsequent cross
sections that were measured at lower discharges
show little additional change.

Hassayampa River

The Hassayampa River drains an area of about
1,500 mi2 from near Prescott in the north through
Wickenburg and south to the Gila River near
Goodyear (fig. I). Downstream from the gaging
station, Hassayampa River near Morristown, the
river becomes entrenched in the alluvium of the
Hassayampa Plain, a large alluvial basin between
the White Tank Mountains on the east and the low-
er Belmont Mountains on the west. The upper
reaches of the Hassayampa River are characterized
by steep, high-energy channels that have gravel

11 16 21
JANUARY 1993

6

26

31 5 9
FEBRUARY 1993

o

Figure 9. Daily mean discharge and cross-sectional area, Gila River at Estrella Parkway, near Goodyear,
Arizona, 1993.

14 Determination of Channel Change for Selected Streams, Maricopa County, Arizona