Cal. Food & Agric. Code § 7275

(a) The department is authorized to operate a government-volunteer partnership Adopt-A-Riverway Program.
(b) The department may receive funds or services from any person to assist a weed management area in implementing an integrated weed management plan, pursuant to this article.
(c) Adopt-A-Riverway Program activities may include the following activities, provided the activities are completed as part of an approved integrated weed management plan and are coordinated with the responsible local agency:
1. (1) Planting and establishing native seedling trees, native grasses, and wildflowers along the adopted riverway.
2. (2) Removal of litter and noxious and invasive plant species.
(d) Adopt-A-Riverway Program activities shall be conducted only on publicly owned land unless permission is granted by the owner or owners of private property for program activities to take place on their property as well.
(e) Activities undertaken pursuant to subdivision (c) are subject to review pursuant to the California Environmental Quality Act (Division 13 (commencing with Section 21000) of the Public Resources Code) and any state or locally adopted river management or conservancy plan.
(f) The secretary may request a local authority to authorize a courtesy sign to be placed on a county highway or city street, near the riverway, pursuant to Chapter 2 (commencing with Section 1975) of Division 2.7 of the Streets and Highways Code.
(g) It is the intent of the Legislature that the duties and responsibilities of the department, as provided for in this section, be accomplished by utilizing existing staff resources, as available.