Canyon County, ID Environmental Rules: Stormwater Management (2026)

Canyon County's subdivision ordinance addresses stormwater at two points in the platting process. 3, every preliminary plat application filed with the Development Services Department must include, as part of its Proposed Utility Methods section, a statement describing the type of stormwater disposal facilities proposed, along with any evidence the county requires regarding the design and operation of the proposed stormwater system. Later in the process, § 07-17-31(2), Required Improvements, gives the Planning and Zoning Commission or hearing examiner authority to recommend, and the Board of County Commissioners authority to require, subdivision improvements such as curbs, gutters, sidewalks, streetlights, ribbon curbing, swales, and stormwater retention and disposal facilities as a condition of approval.

Together these sections mean stormwater disposal is disclosed at the preliminary plat stage and can be turned into a binding improvement requirement by the Board before a final plat is approved. Hillside developments face an additional layer of drainage review under § 07-17-33(1)C, which requires a preliminary and final grading and drainage plan for any hillside subdivision. These subdivision-stage stormwater rules apply only to land divisions in unincorporated Canyon County, Idaho; land inside Caldwell, Nampa or the county's other incorporated cities is platted and reviewed under that city's own subdivision and stormwater standards, not this chapter.