Kolb Road Basin GIS analysis

Kolb Road Basin: a GIS review and conceptual exploration Matthew Bossler Masters Student, University of Arizona Department of Landscape Architecture and Planning LAR 623, Landscape Planning 04‐05‐09

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Introduction and Project Goals This study aims to create a retrofitted vision for the Kolb Road regional detention basin using a GIS‐based planning model. This analysis builds upon a previously‐prepared literature review and research proposal by the author describing the primary and secondary functions of multiple‐function basins within the metropolitan Southwestern U.S., including: 1.) Exemplary regional case studies, 2.) A review of existing detention and retention basin design manuals for Pima County, and 3.) A program of research to ultimately create an easily‐understandable design manual for both landscape architects involved in such designs. Components of this research will include a survey of involved professional (Landscape Architects, Civil Engineers, Hydrologists, Restoration Practitioners, etc.,) visits to the most referred‐to multiple‐use basins with the Southwestern U.S., a comparative graphic typology of general design solutions, and an analysis of the relationship between civil engineers and landscape architects involved in this design arena. Fundamentally, I am interested in looking for opportunities to increase the community value of unique and under‐designed riparian amenities within arid metropolitan areas, detention and retention basins.

Concurrently, I would like to undertake a program of analysis and retrofitted design of the Kolb Road Basin in southeastern Tucson, Arizona, in conjunction with Pima County Regional Flood Control District (PCRFCD.) I was originally alerted to the potential for ecosystem and recreational function at Kolb Basin while conceptually master‐planning a potential public‐private partnership Metro Park incorporating the Rodeo regional detention basin (PCRFCD) along Valencia Road.

A 2007 report presented by PCRFCD at the 2007 annual Arizona Hydrological Society meeting, entitled “Multipurpose Benefits of Regional Detention/Retention Facilities in Pima County,” evaluated the potential costs of saved water, ecosystem benefits, recharge potential, and recreational benefits for retrofitted design of each of seven regional detention basins (Postillion 2007.) This report found that while the smaller‐capacity Rodeo basin (395 ac‐ft) has limited riparian connectivity and poor vegetation

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cover, the much larger Kolb Road basin (940 ac‐ft.) is moderately rated in both areas. In addition, I learned of a greenway master‐planning effort being undertaken by friend and Olsson Associates staff member Wendy Loetze for the City of Tucson, in anticipation of further growth within the Julian Wash watershed.

In addition to the ecophysiological constraints of Rodeo basin, an additional constraint is that a local firm (Wheat‐Scharf Associates) has been contracted by the City of Tucson to work in conjunction with PCRFCD to design a city Metro park incorporating private developments. Therefore, in order to avoid duplicative design work, the Kolb Road basin has been selected as a county property with which to explore multi‐use design.

Problem Statement In order to determine appropriate uses for the Kolb Road detention basin, four questions must be answered in individual fashion. Is the Kolb Road Basin an appropriate location for: ¾ HAB: Restored riparian habitat from the perspective of optimal habitat value? ¾ PAR: Community/Regional park amenities for residents of SE Tucson (Parks and Rec perspective)? ¾ PAFC: Park amenities from traditional perspective of flood control and conveyance/risk management? ¾ PANR: Park amenities from perspective of non‐residential developers (UASTP and others)?

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Figure 1: Kolb Road Basin is surrounded by the University of Arizona Science and Technology Park (UASTP), Kolb Road, and the Burlington Northern Santa Fe/Amtrak Railroad.

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Study Area For general reference, the University of Arizona Science and Technology Research Park (Figure 1, in yellow) is bounded by Kolb Road on the West, Interstate 10 on the Southwest, Rita Road on the East, and the Union Pacific/Amtrak Railroad line on the Northeast, roughly forming a parallelogram. The Science and Technology Park is generally characterized by three main areas: the Kolb Road basin in the Northwest corner (in blue), an office complex along Rita Road, and mostly desert scrub in between.

Recognizing that growth in SE Tucson is limited by barriers trending SE‐NW (I‐10, BASF/AMTK Railroad,) and the districts of David Monthan Air Force Base (DMAFB; Figure 1, feature #1,) Tucson International Airport (TIA; off‐map,) a complex of prisons along Wilmot Road southwest of I‐10 (#2) and propelled by recreational and habitat amenities of Pantano Wash (#3,) Fred Enke Golf Course (#4,) Pima County Fairgrounds (#5,) Rodeo Basin (proposed; #6,) Fantasy Island Trail Park (#7,) the study area has been loosely defined by a perimeter square approximately eight miles on each side (in purple.)

Product As described above, in order to ultimately determine appropriate programming for the Kolb Road Basin, the following products must be produced: ¾ 4 maps depicting optimal locations for each of 4 perspectives from Problem Statement ¾ Comparative maps synthesizing two or more perspectives ¾ Off‐site conceptual design diagram ¾ On‐site conceptual design diagram Recognizing time constraints and current data availability, the study presented in this paper will include: ¾ Off‐site conceptual design diagrams (2) from HAB and PAR considerations ¾ Off‐site conceptual synthesis design diagram ¾ HAB (restored riparian habitat) suitability map ¾ PAR (park amenities, residential) suitability map

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¾ On‐site conceptual design diagram, including siting of approximately 23 acres of constructed riparian habitat

In introductory conversations with PCRFCD, an opportunity arose. Marisa Rice, Chief Hydrologist, has informed me that inclusion of mitigated riparian habitat within a PCRFCD basin is being considered as a result of proposed disturbance to 23 acres of riparian habitat by Granite Construction, which operates a major sand and gravel operation approximately 3.75 miles to the southwest. In addition, the district is in need of an update to the Multiple‐Use Retention and Detention Basin Design Manual, including design guidelines for reestablishing riparian vegetation. The 1986 version of this manual, prepared by the Planning Center and McGann and Associates, contains valuable descriptions of potential multiple functions, basin configurations, technical design standards, and a recommended planning and design process; however, the design guidelines within this report were prepared “to be applied to various, as yet unidentified sites in Pima County,” and the following recommendation is contained within: (PCTFCD 1986) These guidelines have been prepared to aid in the initial development of basins of this type. To remain useful it is recommended that these guidelines be reviewed and updated after the construction of two or three such basins.

It is the hope and proposal of this author that the results of my thesis can be incorporated into the update of the 1986 report, both within the realm of riparian habitat reconstruction and design of recreational amenities, as well as in the realm of master‐plan programming and design.

The Kolb Road detention basin was designed by Cella Barr Associates in 1983 with the expressed purpose “to reduce peak discharge rates (resulting from severe storm events) for the Julian Wash as it passes through developed, southern portions of the Tucson area,” and did not include other functions

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(PCFCD 1983.) As such, the design guidelines of the 1986 manual were not incorporated into the original design of the basin.

Perhaps the only basin to which these design guidelines have been applied since its inception is the Ajo Basin, which, in 2002, was re‐designed to create the Kino Environmental Restoration Project (KERP) and off‐site irrigation of Tucson Electric Park (Postillion 2007.) KERP demonstrated that, within the urban fabric of Tucson, a functional floodway could not only provide a source of water for off‐site turf irrigation, but also create significant wildlife habitat, and adjacent recreational use. Where it falls short, in the opinion of this author, is in the allowed interaction between park visitor and riparian area.

In short, while the visitor can see the riparian areas, they cannot enter them or circulate around or through them. According to an email exchange on March 23, 2009, with Jennifer Becker, Pima County Regional Flood Control District Hydrologist, recreational amenities, including a golf course, were eliminated from the design in order to stay within the requirements of the primary funding source, the US Army Corps of Engineers ecosystem restoration program. The reasons for this limitation were likely three‐fold: to prevent human contact with poor‐quality water, prevent visitors from being in harm’s way during flood events, and reduce intrusions into prime wildlife habitat of a hydro‐riparian nature, the latter of which is considered a sacrifice of the integrity of the habitat. While USACE allows a limited amount of pedestrian recreational amenities to go through and around the habitat, any more is generally not allowed.

While the programming scope of KERP seems to have minimally prioritized riparian interaction, this is not always the case. While the Tres Rios demonstration wetlands at the confluence of the Salt, Gila, and Agua Fria Rivers in the Phoenix metropolitan area was originally undertaken by the U.S. Bureau of Reclamation (USBOR,) the project has been picked up by USACE, in conjunction with the city of Phoenix and Maricopa County Flood Control District to incorporate “sustainable and diverse native

riparian habitat,” flood control, and environmental education and recreation (Megdal 2005.) In

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Pima County, the Swan Wetlands, on the southern banks of the Rillito River, has been designed and constructed to incorporate the Rillito River greenway river trail, flood control access roads, native xeroriparian and upland plantings in a manner that encourages exploration and participation by the recreational visitor. Considering these three examples, it seems clear that while off‐trail recreational exploration and participation is deemed a compatible use for upland and xeroriparian constructed habitat through USACE Ecosystem Restoration dollars, the same uses within meso‐ and hydroriparian areas (cottonwoods, willows, emergent and submergent vegetation,) is deemed incompatible.

However, two characteristics of the project at hand suggest that this incompatibility may not need to be addressed at the Kolb Road basin. First, the mitigated riparian habitat to be funded by Granite Construction is of a xeroriparian nature. Second, USACE Ecosystem Restoration Program is not currently funding this project, and existing Pima County guidelines for the design of mitigated riparian habitat do not necessarily disqualify the interaction between meso‐ and hydroriparian vegetation and recreation (PCTFCD 2001.) While, for xeroriparian areas, “the mitigation area must be one continuous area in a density that creates habitat,” there is no language that precludes recreational involvement.

In order to create a conceptual framework for the regional location and internal design of habitat and recreational uses for the Kolb Road basin, this study borrows from theories of landscape ecology. The “single large or several small” theory holds that the division of a habitat patch with a linear intrusion such as a recreational path not only decreases the overall area of a patch, but further decreases its value by increasing the relative amount of “edge habitat,” or that which is negatively affected by such processes as invasive species proliferation and disturbance by human activity.

Therefore, while recreational intrusions can occur within a patch of mitigated xeroriparian habitat, the overall acreage of functional habitat is reduced. On a larger scale, while “stepping stone” habitat patches disconnected from other habitat patches and corridors do have value to more migratory

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animals such as passerine birds, these patches, by acre, have less habitat value than an acre connected to a habitat network (Dramsted et al. 1996; figure 2.) The design implication of this theory for the Kolb Road basin is that a mitigated xeroriparian habitat intersected by recreational trails will require a greater overall acreage than a “continuous area” without such disturbances (figure 3.) Therefore the costs to the client required to mitigate riparian habitat must be calculated for such a continuous area. Additional costs to introduce recreational use and thus increase overall acreage must be funded by other participating entities. In the case of the Kolb Road basin it is assumed that these costs will be carried by either Pima County Regional Flood Control District or City of Tucson Parks and Recreation Department, who has expressed support for such an idea.

Another consideration for the programming of the Kolb Road basin is to question its value within the City of Tucson’s parks network. The City of Tucson Parks and Recreation Department’s Ten Year Strategic Plan describes that this network is composed of individual nodes/parks with “service areas” extending in a specified radius to surrounding residential neighborhoods (CTPR 2006; figure 4.)

Park service areas extend to 7 miles for Regional Parks, 2.5 miles for Metro parks, 1 mile for community parks and ½ mile for neighborhood parks.

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Figure 2: The “Single Large or Several Small” concept is best understood by considering the spatial relationship between habitat patches, connecting corridors, and disconnected stepping stones.

Figure 3: Within a connected habitat network, larger patches can contain component patches of varying habitat value. By locating minimal intruding pathways through less sensitive areas within close proximity of highly sensitive habitat, human‐riparian interaction is achieved without sacrificing habitat integrity.

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Figure 4: Park service areas are defined by proximity of surrounding residential areas within service radii.

Site Inventory

As described above, the Kolb Road basin is bound by Kolb and Rita Ranch roads, the railroad

line, and I‐10. It is 256 acres in area. For comparison, City of Tucson Metro parks, meant to serve residents within a 2.5 mile radius, are designed to be between 40 and 200 acres in size (CTPR 2006.)

Data of a natural and physical character will be useful in assessing the suitability of particular areas within the site that are appropriate for riparian habitat mitigation. These include proximity to existing linear riparian features, the extent of the upstream watershed, David Monthan Air Force Base flight approach zones, and soil type and vegetation community type within the basin and adjacent areas.

Existing and proposed land use and park data, DMAFB flight noise zones, and eco‐physiological data, will

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help answer the recreational suitability of portions of the site. These data will include general categorizations of ecosystem type and high‐flow/low‐flow areas, and proximity to existing and proposed recreational and commercial parcels. Data of this nature have been acquired directly from Pima County Flood Control District, Arizona Land Resource Information System (ALRIS,) Olsson Associates, and other Pima County sources.

Site Analysis: Habitat (HAB) Conditions that are appropriate for riparian habitat mitigation are areas containing high‐quality soils, close to major or minor existing biological corridors, and at locations that are outside of flight approach zones. The overall model combining these conditions is presented in figure 5.

In order to create a soil suitability layer, the model begins with a Hydrologic Soils Group Map provided by Pima County Regional Flood Control District. This layer has clearly been created based upon Natural Resource Conservation Service (NRCS) soil unit maps, and recategorized to fit within the riparian habitat types identified within the county’s riparian ordinance. Generally, these soil types are described by their permeability, with “A” being the least permeable and “D” being the most permeable. Referring to the Soil Conservation Service National Engineering Handbook 4, the Pima County Hydrology Procedures, PC‐Hydro User Guide, 2007, describes this as “Each soil series is classified into one of four hydrologic soil groups (HSG) according to their minimum infiltration rate obtained for bare soil after prolonged wetting (SCS 1985).” By opaquely overlaying this layer on an ALRIS aerial photograph taken in 2005, I was able to compare the extent of the four existing layers with the absence or presence of riparian vegetation. While it was expected that permeability would inversely correlate with the presence of supported riparian habitat, as would be expected from a water‐harvesting perspective, it was found that while the least permeable soils (“A”) supported the densest and highest‐quality riparian vegetation, the least amount of riparian vegetation was associated with those of intermediate permeability (“B” and “C,”) while a moderate amount of riparian vegetation is supported by soils of high

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permeability (“D”; figures 6 and 7.) Therefore, these soil types were recategorized by attribute to create three soil suitability types of high, low and medium.

Figure 5: Habitat suitability model

Figure 6: As soil becomes more porous, permeability and rate of infiltration increases (Image courtesy of National Repository of Online Courses)

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Figure 7: Hydrologic soil groups were recategorized to create a soil suitability layer.

Pima County Department of Transportation‐defined major riparian areas were buffered with distances of 0.5, 1 and 2 miles in order to demonstrate proximity of the project site to existing, yet disconnected major biological corridors. A Pima County‐derived washes layer was also buffered, but with a single distance of 300 feet to recognize their habitat proximity value to a lesser extent than major corridors. An air‐traffic compatibility layer was created by recategorizing a DMAFB approach zone shape file provided by the county to recognize the incompatibility between low‐flying planes and high‐flying birds and bats that may be attracted to a constructed riparian amenity.

In order to analyze this data, three scales of view were chosen. The first, at the study area level, revealed two major findings, whilst temporarily disregarding the soil suitability layer (figure 8.) First, there were no land use restrictions due to the flight path. Second, Kolb Road basin is located between two major riparian corridors and along a minor riparian corridor, indicating that it has value as a “stepping stone” between major biological corridors, and as a patch connected to minor biological corridors.

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Figure 8: A study area analysis reveals that Kolb Road basin may act as both stepping stone and patch between and among biological corridors, and that the DMAFB flight approach zone does not present a problem for high‐flying birds.

The second scale of view focuses upon an area slightly larger than the perimeter of UASTP (figure 9.) This scale reveals that the Julian Wash watershed above Kolb Road Basin includes multiple washes with moderate soils for riparian vegetative growth. This suggests that biological connections to or through UASTP and the areas to the northeast would be beneficial to a local riparian network.

A third scale of view at the scale of the perimeter of the Kolb Road basin revealed that it is composed of three major soil units, the central of which contains soils and drainage patterns more appropriate for riparian vegetation (figure 10.)

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Figure 9: Minor biological corridors with suitable soils for riparian habitat extend through the Julian Wash watershed upstream of the Kolb Road basin.

Figure 10: Kolb Road basin includes a central soil unit of moderate suitability.

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Ground‐truthing was then conducted by the author in order to identify more fine‐scale avoidance and opportunity areas for restoration (figure 11.) Existing riparian areas to avoid for future restoration include siltifying areas at drop structures (left red area,) and those areas upstream of levees (right red area.) Currently unvegetated areas to target for future restoration include slightly higher grounds within the basin (blue area), basin slopes (figure 12,) and actively bladed areas (figure 13.)

Figure 11: Ground‐truthing is essential to identify opportunities (in blue) and avoidance areas (in red) for future habitat mitigation areas that escape detection from remote GIS analysis.

Figure 12: The 4:1 unstabilized side slopes of the basin are opportunities for maintenance, habitat, and recreational improvements.

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Figure 13: Areas that have recently been bladed by PCRFCD are in early stages of seral development, making them areas where mitigation efforts can only create more complex habitat structure.

Site Analysis: Parks and Recreation (PAR) Conditions that are appropriate for recreational amenities from a residential or Parks and Rec perspective are outside of the high flight noise decibel zone, close to existing and proposed residential and commercial areas, connected to existing or proposed greenways, and those that fill a gap in Tucson or Pima County Parks and Recreation Department’s service areas. The overall model combining these conditions is presented in figure 14.

Airplane noise can reach decibels that make gathering uncomfortable. The flight noise decibel levels have been recorded within ground areas underneath the flight path of DMAFB and summarized by Airport Noise Zones categorized by 5 decibel layers. Davis Monthan Air Force Base‐Tucson Joint Land Use Study, conducted in 2006, recommends to “Limit exposure of people and noise‐sensitive activities

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to high noise levels,” and considers “Noise Sensitive Activities” to be “outdoor activities where conversation or quiet is important.” Decibel zones depicted in the available shape file range from 60 to 75 decibels, which is roughly equivalent to the sound of a business office (figure 15.)

Olsson Associates, a national engineering and design firm, was contracted by the City of Tucson to site and design the Julian Wash Greenway. Recently, construction documents locating the greenway along the northern rim of the Kolb Road basin and further along the northern side of UASTP were approved by PCRFCD. Olsson graciously provided their GIS layer of greenways for this analysis. A Pima County‐derived shape files included both City and county park facilities; individual park types (Metro park, neighborhood, etc.) were queried by type and saved as separate files. These files were then displayed using different colors for the purpose of viewing what types of existing park facilities are within the study area.

Existing residential developments apparent on ALRIS 2005 aerial photos were digitized to shape files. A PCRFCD‐derived planned development shape file was queried to identify and separately save proposed residential development. These two layers were then unioned to create a “combined residential layer.

Finally, the perimeter of the Kolb Road basin was buffered with radii corresponding to city defined park service areas in order to display potential service areas by type.

Simply two scales of view were used to analyze Parks and Recreation suitability. The first was once again at the scale of the study area (Figure 16.) This scale revealed that the Kolb Road basin is an ideal location as major park node along Julian Wash Greenway, with metro‐ or regional park service area to an underserved residential population. An intermediate scale of view demonstrates that the basin just narrowly avoids the 60 decibel noise disturbance area, which as discussed above, is not loud enough to be a major disturbance to gathering (Figure 17.)

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Figure 14: Parks and Recreation suitability model

Figure 15: 60 decibel noise is louder than conversational speech, but quieter than a business office.

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Figure 16: A study area analysis demonstrates the location of existing and proposed residential developments (in blue) falling within/overlain by service radii from a potential Kolb Road basin park.

Existing parks do not fall within a Metro park radius of the Kolb Road basin.

Figure 17: Noise levels resulting from DMAFB airplanes over Kolb Road basin are lower than 60 decibels.

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HAB/PAR Suitability Summary and Synthesis In summary, this GIS analysis indicates three significant findings. First, Kolb Road basin could serve as important riparian patch connected to a minor corridor (Julian Wash) and as a ‘stepping stone’ between major riparian corridors. Second, it could be appropriate as a park serving underserved neighboring communities in a metro‐park or regional park service radius. Third, the basin could serve as a major recreational node along the soon‐to‐be constructed Julian Wash Greenway.

Synthesizing this analysis, a few design implications are made apparent. First, future designs should work to preserve current riparian areas both within and outside of the basin. Second, mitigated riparian areas should be sited on good soils with little existing vegetation. Third, traditional active recreation playing fields should be sited on poorer soils with little existing vegetation. Fourth, parcels for purchase for parking lots and habitable structures to support a Metro park should be identified. Fifth, areas for human‐riparian area interaction without major detriment to ecosystem structure should be carefully located according to the theoretical diagram presented (figure 3.) Finally, the two most important layers to consider for further design are soil suitability and the aerial photo.

With that in mind, a simplified synthesis base map emphasizing soil suitability and identified

opportunities and constraints via the aerial image was created for the purpose of design (figure 18.)

Over this, a hand‐generated diagram was drawn locating two riparian areas to be preserved, a continuous 23 acre riparian area to be constructed, two active recreation areas, parking and habitable structures, trail connections among them, and drainage patterns (figure 19.)

The proposed location for constructed riparian habitat “bridges the gap” between two existing

riparian areas that have been designed to be preserved, and will be fed by all three major drops structures by excavating the basin bottom. Low‐suitability soils for riparian reconstruction with little existing habitat cover offer ideal locations for active recreation fields. Parking and habitable structures can be located along the top of the dam, which is stabilized by and adjacent to Kolb Road. Trail access

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transverses the existing 4:1 slope, which will be re‐contoured to support ADA‐acceptable trails and water‐harvesting planting areas. Trails additionally extend to the proposed Julian Wash Greenway on both the east and west.

Conclusion This GIS review and conceptual exploration has clarified the future design possibilities for Kolb Road basin regarding tow major considerations. Is it an appropriate location for restored riparian habitat from the perspective of optimal habitat value? Is it an appropriate location for community/regional park amenities for residents of SE Tucson (Parks and Rec perspective)? The answer to both is a resounding “YES!” and the design solution to optimize both lies in the siting of recreational disturbances throughout low‐sensitivity habitat and around, yet still near to sensitive habitat.

Future questions to be answered, besides the two ignored from the original four questions, that have come to light as a result of this study include: Can introducing a third dimension into design open up more possibilities for interaction between recreating visitors and sensitive habitat (bridges and structures?) Is the basin perhaps more appropriate as a natural‐resource park, eliminating the need for traditional activity areas? Will SE Tucson continue to grow as planned any time within the near future?

Are there other restrictions regarding the Davis Monthan Air Force Base that have been overlooked?

For the time being, these questions will be left for another day.

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Figure 18: Opportunities and constraints are most simply displayed by viewing the aerial photo and soil suitability layer.

Figure 19: Proposed design locates component places and circulation within and around the basin.

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Works Cited

Arroyo Engineering. Pima County Hydrology Procedures, PC‐Hydro User Guide. Tucson, AZ. 2007.

City of Tucson Parks and Recreation (CTPR). City of Tucson Parks & Recreation Ten‐Year Strategic Service Plan. Tucson, October 31, 2006.

Dramstad, Wenche E., James D. Olson, and Richard T.T. Forman. Landscape Ecology Principles in Landscape Architecture and Land‐Use Planning. Washington, D.C.: Island Press, 1996.

Megdal, Sharon B. Environmental Restoration Projects in Arizona: The U.S. Army Corps of Engineers’ Approach Final Report, Water Resources Research Center, University of Arizona.

Tucson, AZ, June 2005.

Pima County Flood Control District (PCFCD). Kolb Road Detention Basin Hydraulic Design Report, by Cella Barr Associates. Tucson, 1983.

Pima County Transportation and Flood Control District (PCRFCD). Regulated Riparian Habitat Mitigation Standards and Implementation Guidelines, by Novak Environmental. Tucson, 2001.

Pima County Transportation and Flood Control District (PCTFCD). Guidelines for the Development of Regional Multiple‐Use Detention/Retention Basins in Pima County, Arizona, by The Planning Center and McGann and Associates. Tucson, 1986.

Postillion, Frank, Evan Canfield, Julia Fonseca, and Kathleen Chavez. “Multipurpose Benefits of Regional Detention/Retention Facilities in Pima County.” Paper presented at 2007 Regional Water Symposium, 20th Annual Arizona Hydrological Society Symposium, Sustainable Water, Unlimited Growth, Quality of Life: Can We Have It All? Tucson, AZ. August 29 – September 1, 2007.

Additional sources

American Society of Civil Engineers. 2001. Standard Guidelines for Artificial Recharge of Ground Water. Environmental and Water Resources Institute, American Society of Civil Engineers, Reston, VA.

Brightman, Darrin William. “Overlooked Oases: Wildlife Habitat in Urban Flood‐Control Basins.”

Masters Report, University of Arizona, 2004.

Cella Barr Associates. Julian Wash Hydrologic Study. Tucson, 1993.

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Willott, Elizabeth. “Restoring Nature, without mosquitoes.” Restoration Ecology 12 (2004): 147‐153.