Tortolita Fan

To provide comments on this watershed for consideration in the Floodplain Management Plan, contact Greg Saxe
Planning Manager
(520) 724-4633.
The Tortolita Fan watershed includes the Cottonwood, Prospect, Cañada Agua and Hardy washes that drain the southwestern slopes of the Tortolita Mountains.  Originating from the Tortolita Mountains and continuing on the relatively gentle slopes of alluvial fans, these washes terminate in the geologic floodplain of the Santa Cruz River. Flood risk in this alluvial fan includes poorly defined washes with the potential for significant changes in flow direction due to flows breaking out of existing channels and continuing downhill via unpredictable new paths. Floods develop quickly and may carry a significant amount of sediment and debris, which may cause damage and further divert flows in unpredictable ways. Sheetflow flooding is the dominant type of flooding that affects residents of this area. While sheetflow flooding is generally fairly shallow, it is also very widespread and makes accessing properties difficult. This is especially true due to the prevalence of unmaintained dirt roads. In sheetflow floodplains, it is important to protect your home from flooding and obtain flood insurance, but it is not appropriate to prevent your property from flooding as this makes flooding worse for neighbors. This watershed is comprised of 38,838 acres and contains 10,130 acres of SFHA, 7,544 acres of locally identified floodplain and 6,824 acres of Pima County Regulated Riparian Habitat.

Flood Hazards


Click HERE to view the watershed map
Click HERE to view the outreach brochure
Click HERE to view the hazard map

Floodplain Studies

Floodplain Study FP-024-1993 - Tortolita Area Basin Management Plan, Ph I, Ph IIB, Cella Barr Associates, 8/3/1993

Floodplain Study FP-098-2019 - North Ranch Technical Data Notebook for Hydrologic and Hydraulic Mapping, Arroyo Engineering, 03/14/2019.

Erosion Studies

Floodplain and Erosion Study FP-019-1992 - Tortolita Mountains Geomorphic Assessment, Arizona Geological Survey, June 1992  

Areas of Interest (Known Issues, Gaps, Problems and Needs)

Issues Provided by Public and Stakeholder Input

No issues have been identified to date.

Issues from the District Flood Response Manual

8.17.1 Data Gathering Needs
• No site specific issues identified.

8.17.2 Frequently Flooded Structures and Properties Subject to Damage
• No site specific issues identified.

8.17.3 Infrastructure
• Drainageway # 1841 (poly ID 3532) in Countryside subdivision experienced bank erosion in heavy 2018 monsoon season, requiring repairs. (T12S R12E Sec. 24)
• Drainageway # 3236 (poly ID 3666) in Orangewood North subdivision experienced bank erosion in heavy 2018 monsoon season, requiring repairs. (T12S R13E Sec. 30)
• Drop structures, grates and other infrastructure on Drainageway #s 2718 (poly ID 3806), 666 (poly IDs 3804 and 3805) in Sunset Point Number 2A subdivision requires inspection after every intense storm event in the area, as the grate often gets clogged with debris, causing ponding. In 2018, water nearly entered a garage due to the ponding. (T12S R12E Sec. 25)

8.17.4 Safety Concerns
• Hartman Lane as it enters Marana (near Countryside Vista and Countryside Terrace) is subject to flooding and can become impassable, especially at the crossing near Wood Owl Dr. Also, the wash south of Condor Dr. is prone to filling up with sediment. (T12S R12E Sec. 24)



Recommendation of Actions and Floodplain Management Strategy

This section to be completed based on feedback received through the planning process.