Flagstaff, AZ Environmental Rules: Erosion Control (2026)

Flagstaff's Engineering Design Standards, Chapter 13-17, Erosion Control, require that all disturbed areas within a project site, and any adjacent land disturbed by construction, be stabilized using the materials, best management practices and erosion control plans described in the City of Flagstaff Stormwater Design Manual. The owner, developer or contractor is responsible for complying with the National Pollutant Discharge Elimination System permit program, which means filing a notice of intent with the Arizona Department of Environmental Quality, and for preparing and carrying out a stormwater pollution prevention plan (SWPPP) for the site under ADEQ and City engineering standards.

Chapter 13-10's structural section standards add numeric slope thresholds: every publicly and privately built cut or fill slope must be protected from erosion, and any slope steeper than 2:1 is barred outright unless a registered geologist or other qualified professional certifies its stability with a quantitative geotechnical analysis. Slopes steeper than 2:1 that exceed six feet in height must use rigid or semi-rigid erosion control products, and all slopes of 3:1 or flatter, plus shorter 2:1 slopes under six feet, must be reseeded under Chapter 13-17; the City Engineer can require filter fabric to hold the seed and mulch in place until vegetation establishes.

Elsewhere in the Engineering Design Standards, cut or fill slopes over six feet and steeper than 3H:1V must be covered with straw, coir or natural-fiber erosion control blankets, with coir or blended blankets reserved for the steepest slopes, low-flow channels and multi-season protection.