FLOOD05012

• County: Statewide
• Basin: Statewide
• Title: Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
• Date: 1/1/1998
• Prepared For: Maricopa County Arizona
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

Skunk Creek above Interstate 17

Drainal!e area:

Latitude 33043'56", longitude 112006'57", Reach begins about 1 ,000 ft upstream
from streamflow'gaging station 09513860, Skunk Creek near Phoenix.

64,9 mi2.

Reach location:

Bed-material size:
Channel descrintion:

d50 = 88 mID (0,29 ft).

The constructed channel is fairly uniform, and bed material is mainly cobb1e,sized
clasts partially surrounded by finer silt, and sand,sized material. Vegetation consists
of brush of moderate spatial density and grows randomly throughout the channel.
The stream is ephemeral and flow is unregulated,

Remarks:

Nine verification measurements were made for several stages of vegetation growth
within the study reach. The first measurement on March 1, 1991, was made when the
vegetation was fully grown (average height, about 5 ft), Verifications 2-5 were made
after the reach had been artificially maintained and cleared of all the vegetation,
Verifications 6 and 7 were made during a period of regrowth (average height was
about 2 ft), Verifications 8 and 9 were made after the vegetation was again fully
grown (average height, about 5 ft). Although flow magnitude was greater for the
postmaintenance measurement of January 26, 1995, compared to the
premaintenance measurement of March 1, 1991, the water-surface elevations were
lower (fig, 5A). The vegetation was little affected by flow for all measurements,
According to survey data, channel geometry and bed conditions did not appear to
change significantly after clearing of the vegetation, For the flow of September 28,
1995, the suspended, sediment concentration was 198,8 mg/L and was considered
wash load. Suspended-sediment concentrations probably did not exceed wash,load
conditions for any of the verification measurements,

Table 3. Flow data and computed roughness coefficients, Skunk Creek above Interstate 17

Discharge, in cubic Roughness
Condition of reach Date of flow feet per second coefficient Rating
Premaintenance of vegetation 03-01-91 618 0,048 Good
Postmaintenance of vegetation 01-26-95 723 ,031 Fair
Do, 01-05-95 393 ,034 Fair
Do, 01-26-95 180 .035 Good
Do, 01-05-95 168 .037 Good
Partial regrowth of vegetation 09-28-95 822 ,035 Fair
Do, 11-01-95 500 ,039 Fair
Regrowth of vegetation 08-14-96 403 ,048 Fair
Do, 09-02-96 215 ,052 Fair

16 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona