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Tucson Stormwater Management Study (TSMS) Vegetative Volume Classification

Much of the riparian habitat along the naturally vegetated watercourses within the City has been qualitatively identified and tabulated within the TSMS, Phase II report titled: "Natural Riparian Habitat Inventory" March 1995. This study established the link between wildlife habitat value and vegetative volume of riparian habitats. The identified riparian habitats were classified as Hydroriparian, Mesoriparian, Xeroriparian, and Disturbed and Sparsely Vegetated habitats. Hydroriparian habitats are usually associated with perennial watercourses. Mesoriparian habitats are usually associated with perennial or intermittent watercourses or shallow ground water. Xeroriparian habitat is supported by intermittent or ephemeral stream flows that increase the amount of water available to plants beyond that available by direct rainfall. Xeroriparian habitats commonly contain the same plant communities as the adjacent upland vegetation, but have larger plants and denser growth due to the availability of water. Xeroriparian habitats were further classified based on bank-side vegetative volume [volume of vegetation (m3) above a specific ground area (m2)] and habitat characteristics. The vegetative volume classes breakdown as follows: Xeroriparian High habitat = 1.26 m3/m2; Xeroriparian Intermediate habitat = 1.03 m3/m2; Xeroriparian Low = 0.62 m3/m2. Disturbed and Sparsely Vegetated watercourses are those that have little or no vegetation due to human alteration. The vegetative volume classification values are approximate (overlapping) and need to be combined with the following habitat characterizations for appropriate classification:

Xeroriparian High
Vegetation volume habitats are typically found along large, well-developed (i.e., regional) watercourses. Large trees, 16 to 20 feet or greater in height, are common. Trees and shrubs are closely spaced. Understory vegetation is usually present, although it may be fairly sparse due to the dense overstory. The total vegetation volume is relatively high, with the majority of the volume provided by trees. The West Branch of the Santa Cruz at Ajo Way and Mission Road supports large mesquite and blue paloverde, which form a nearly closed canopy, and typifies watercourses with the high vegetation volume habitat.
Xeroriparian Intermediate
Vegetation volume habitats are typically found along the major watercourses. Trees range in size from 6 to 15 feet in height and are more widely spaced than in the high vegetation volume category. A well-developed shrub layer is typically present. The Enchanted Hills Wash, located near the intersection of Ajo Way and La Cholla Boulevard, supports a narrow strand of mesquite, white thorn acacia, blue palo verde, and desert broom, and typifies watercourses with intermediate vegetative volume habitat.
Xeroriparian Low
Vegetation volume habitats typically occur along minor watercourses, but can also occur along reaches of major watercourses. Species composition is similar to that found in the intermediate category, although individual plants are typically smaller and overall vegetation volume is lower. A small, unnamed watercourse at Kennedy Park, sparsely vegetated with white thorn acacia and creosote, typifies watercourses with low vegetation volume habitat.
Disturbed and Sparsely Vegetated
Habitat generally occurs in watercourses that have been disturbed or altered by humans and, consequently, have little or no vegetation. Typically, these disturbances involved some manner of bank stabilization or other management activities. Vegetation in this category is sparse to absent due to previous human disturbance and continued disturbance from scouring action of stormwater runoff events. Channelized portions of Rillito Creek, Alamo Wash, and Tanque Verde Creek, with broad, sandy channels supporting clumps of weedy vegetation and/or small trees and shrubs, are typical examples of watercourses with this habitat category.

The TSMS was based on 1"=400', 1990 aerial photography and the March 31, 1995 City limits. The City has grown substantially in the 13 years since the TSMS study was completed. Over 64 square miles have been added to the City limits. In addition, riparian areas mapped under TSMS have undoubtedly experienced change since the study was completed. Efforts are currently underway to update the TSMS riparian mapping study.

Watercourse alignment with TSMS classifications may be viewed at http://tdotmaps.transview.org/mapguide_mwf_tsms.htm (requires the Autodesk MapGuide Plug-In).

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Critical and Sensitive Wildlife Habitats of Eastern Pima County

The Critical and Sensitive Wildlife Habitats of Eastern Pima County study was completed by Dr. William Shaw in 1986 for the Pima County Department of Transportation and Flood Control District. Habitat mapping used 1"=1000' USGS quadrangle aerial photography. A subset study, Wildlife Habitats in Tucson, A Strategy for Conservation was completed for Tucson. In this study wildlife habitats were grouped into Class I and Class II categories. Class I habitats are extensions of desert riparian habitat from large reserves of public land into the metropolitan area. Class I habitats include Deciduous Riparian Woodlands, Mesquite Bosques, lakes, ponds, and wetlands with adjacent plant cover and important movement corridors for large mammals. Class II habitats include Paloverde-Saguaro communities, Ironwood plant communities and other habitats important to wildlife. Class II habitats are major segments of habitat that are isolated by development from protected areas. The results and recommendations of this study were used in the development of the Environmental Resource Zone (ERZ) overlay zone modification of Tucson Code, Chapter 23, the Land Use Code.

Class I and Class II alignments in and adjacent to Tucson may be viewed at: http://tdotmaps.transview.org/mapguide_mwf_tsms.htm (requires the Autodesk MapGuide Plug-In)

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Other Studies

As Tucson's boundaries expand, habitat data originally collected outside the incorporated limits can be used to determine new watercourse alignments that warrant protection under the City's habitat preservation codes. Pima County has been very active in compiling this type of habitat data in the following habitat studies.

Wildlife Habitat Inventory

Completed for Pima County by the University of Arizona under a Heritage grant from the State Game and Fish Department, Phase I (1993) of this study created a method for interpreting information about land cover and wildlife habitat values within urban and suburban areas. In 1995, Phase II of the study, applied the Phase I methodology to Eastern Pima County. Study results included; a land cover classification system, determination of vegetative attributes for each land cover, a Geographic Information System (GIS) based model for mapping wildlife habitat values, and recommendations for balancing wildlife habitat conservation with development and urban growth. These reports can be reviewed at the Pima County Planning Department or at the Arizona Game and Fish Department.

Pima County Article X of the Floodplain and Erosion Hazard Management Code

Riparian habitat mapping was completed in 1995 for use with Pima County Code, Title 16 (Floodplain and Erosion Hazard Management), section 16.54, Watercourse and Riparian Habitat Protection and Mitigation Requirements. This mapping used 30-meter resolution multi spectral satellite imagery (LANDSAT) to interpret riparian habitat value classifications based on vegetative volume. Five riparian habitat classifications were used: Hydroriparian/Mesoriparian, Xeroriparian A (0.85 m3/m2), Xeroriparian B (0.675 m3/m2), Xeroriparian C (0.50m3/m2), and Xeroriparian D (<0.50 m3/m2). These habitats classifications, shown for areas outside incorporated boundaries, may be viewed at: http://rfcd.pima.gov/

Riparian Vegetation Mapping and Classification, Sonoran Desert Conservation Plan

This planning level mapping effort delineated riparian areas and described vegetative communities by their dominant plant species for use in the Sonoran Desert Conservation Plan. The mapping incorporated existing riparian data and new data inventories. New wash delineation was based on the visual difference between upland and riparian communities, with the assumption that riparian plant communities were denser compared to upland plant communities. The database was developed using 1:24,000, June 1996, USGS Digital Orthophoto Quadrangles.

These maps may be viewed at: http://eim.dot.co.pima.az.us/cmo/SDCPvegPDFs/index.pdf

These data, interpretation of these data, and much, much more may be viewed at: http://gis.pima.gov/maps/mapguide/mgmap.cfm?path=/cmo/sdcpmaps/sdcp.mwf

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