San Luis Obispo County, CA Environmental Rules: Flood Elevation Requirements (2026)

Section 21.03.010(5), Flood Hazard and Drainage, is one of the mandatory design-criteria findings the Planning Commission and Subdivision Review Board must make before approving any tentative parcel or tract map. Subsection (5)a requires evidence that parcels inside a flood hazard combining designation will have "flood free building sites" meeting Title 22 or 23 standards, with sewer, gas, electrical and water systems located and constructed to minimize flood damage, and bars the subdivision from creating a flood hazard for surrounding property. Subsection (5)b caps privately maintained drainage basins at two feet of water under the design storm, measured from the basin's lowest point, requires interior landscaping for erosion control and perimeter fencing that is landscaped to screen and soften it; a shallower-basin exception needs an adjustment under Sec. 21.03.020. Subsection (5)c is the elevation-mapping trigger itself: any new subdivision, including mobile home park proposals, larger than 50 lots or 5 acres, whichever is less, must identify both the Special Flood Hazard Area and the Base Flood Elevation for the site.

An applicant who cannot meet these standards may request an adjustment under Sec. 21.03.020, but the Planning Commission or Subdivision Review Board may grant one only after finding special circumstances affecting the subdivision, no material adverse effect on neighborhood health or safety, and no detriment to the public welfare or injury to other property. A denied map, or a notice of violation recorded under Sec. 21.07.020, is appealable to the Board of Supervisors within fourteen days of the decision.