Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...

Powerline Flood Retarding Structure
Pinal County, AZ
Draft Supplemental Watershed Plan
and Environmental Assessment
vee-shaped incised drainages that carve into them. The drainages create finger-like patterns
overlaying the flat surface of the ground plane.
During the Site Analysis verification site visit, a significant amount of water was observed in the
low flow areas within the reservoirs upstream of the dams from a storm event. The dams and
associated reservoirs and low flow channels have altered the historic drainage pattern in a way that
allows pooling to occur immediately upstream of the dams. This altered drainage pattern created an
ideal environment for the formation of a unique mesquite bosque ecosystem immediately upstream
of the dams. Careful consideration should be given to future development of land and resource
goals and objectives, as well as desired recreation and open space functions to preserve this unique
ecosystem to the extent feasible as part of a larger regional habitat corridor. The preservation of the
mesquite bosque should also be considered for its potential to serve as an open space amenity and
attraction. The significant stand of trees should be considered vegetation of high scenic quality.
The upstream portion of the watershed to the east of the PVR dams is primarily alluvial desert.
Land use is predominantly undeveloped land with some urban development occurring along the
study area fringes north and west of the PVR dams. In these areas, land use includes agriculture,
industrial, and low density housing. The landscape on the upstream side of the dams is unusual for
its native Sonoran Desert scrubland context due to the lushness provided by the mesquite bosques
and pooling in the low flow reservoirs.
The visually dominant dams adjacent to the mesquite bosques constitute another key component of
the landscape character. According to the Sponsor’s descriptions of methods for providing flood
protection for use in scenery and recreation resource assessments of context sensitivity, the
structural method employed in this context can be described as a “semi-hard structural method.”
While the primary objectives of the Sponsor’s Policy for Landscape and Aesthetic Treatment of
Flood Control Facilities are the preservation of natural landscapes and protection of local
community character, flood protection methods vary in their relative ability to complement or
enhance the visual character of the landscape setting and achieve context sensitivity.
The panoramic views provided from the tops of the embankments to the surrounding mountains are
spectacular. Sponsor’s policy is to not allow public access onto the dams. However, where possible,
views to the Superstition Mountains and Tonto National Forest to the northeast, views to the Usery
and Goldmine Mountains to the northwest, and views to the San Tan and distant mountains to the
south should be preserved and focused.
The view sheds as described in this section may be important to traditional (cultural) landscapes.
Consultation with appropriate tribes for proposed project input on traditional cultural properties has
been initiated.
USDA- NRCS Page 4-15 January 2013
Kimley-Horn and Associates, Inc.