Prescott advances green infrastructure designs for Big Chino watershed restoration

Prescott advances green infrastructure designs for Big Chino watershed restorationWorking with The Nature Conservancy, the Arizona municipality has selected two primary erosion control concepts to rehabilitate incised channels, reconnect floodplains, and boost groundwater infiltration.

The Nature Conservancy and consultant Natural Channel Design and Engineering evaluated four restoration concepts for the city-owned property.

Stakeholders selected plans to reconnect abandoned geomorphic channels and install upland low-tech process-based restoration (LTPBR) rock structures.

Geotechnical investigations are complete, with draft designs expected by May 2026 and final designs by September 2026.

City staff have recommended allocating $50,000 in the upcoming water resources budget to serve as initial project seed money.

The City of Prescott, Arizona, is moving forward with a major green infrastructure and source water protection initiative at the Big Chino Water Ranch, partnering with The Nature Conservancy (TNC) to address severe channel incision and erosion. Following a memorandum of understanding signed in early 2025, TNC contracted Natural Channel Design and Engineering (NCDE) to develop assessment and design concepts for the city-owned property. The primary goals are to restore grassland habitat, improve water quality, and slow stormwater runoff to encourage groundwater recharge. During an April 7 meeting of the Council Subcommittee on Water Issues, a TNC representative outlined the severe downcutting impacting the main Big Chino Wash, noting that some sections feature headcuts over six feet deep. This incision accelerates runoff velocities and disconnects the channel from its natural floodplain. To combat the degradation, stakeholders evaluated four distinct erosion control concepts, ultimately selecting two for formal design. The primary intervention, Concept 2, involves reconnecting abandoned geomorphic channels. Historically, sections of the wash were artificially straightened for agricultural purposes. Rerouting flows back into the historic, sinuous channels is expected to reduce water velocity, mitigate erosion, and increase the potential for in-channel infiltration. This will be complemented by Concept 4, which utilizes upland low-tech process-based restoration (LTPBR). This approach involves installing small, hand-built rock structures in the upland tributaries feeding the Big Chino Wash. The structures are designed to arrest smaller headcuts before they reach the main wash, providing a cost-effective, low-impact method to slow incoming flows. Two other proposals were discarded during the evaluation phase. A "plug and spread" concept was rejected due to potential water rights complications, while a large-scale bank sloping project was passed over due to the high volume of required earthwork and the risk of invasive plant encroachment following extensive ground disturbance. NCDE has recently completed a geotechnical investigation utilizing four test pits near the abandoned channels to understand subsurface soil composition and infiltration rates. The consultant is scheduled to deliver a draft design in May 2026, with final designs anticipated in September 2026. To support the project's phased implementation, city water resource staff noted they have recommended a $50,000 allocation in the upcoming municipal budget. The funds are intended to serve as seed money and potential matching funds for future state or federal watershed restoration grants.