Los Angeles County — Hillside Management Areas

Design and Site-Planning Expectations

The County evaluates hillside design as an integrated project, not by treating one favorable feature as dispositive. The Guidelines organize responsive measures into five categories: site planning, grading and facilities, road circulation, building design, and landscaping. § 22.104.070

There is no fixed mandatory count of design measures. As practical guidance, the County identifies four measures per category as typically appropriate, but that figure is a recommendation—not an absolute requirement—and the decision-maker considers the design as a whole. § 22.104.070

Strong site concepts generally:

• Place at least 50% of the development footprint on the site’s flattest areas—slopes below 25%—when those areas do not contain rare, sensitive, threatened, or endangered species. § 22.104.070
• Locate 50% or more of buildings and developable lots within 500 feet of existing sewer, water, and roadway infrastructure. § 22.104.070
• Use previously graded or disturbed land before extending development into undisturbed hillside areas. § 22.104.070
• Cluster structures and use shared driveways when that reduces grading and site disturbance. § 22.44.1350
• Design buildings, pads, streets, and driveways to follow natural contours and minimize landform alteration. § 22.44.1350

A design review inquiry may be useful early, but design review requirements for a particular HMA project are not found in source materials. Verify the applicable permit path with the jurisdiction.

Grading, Slopes, and Drainage

New development is generally prohibited on slopes of 50% or greater. The cited standard allows exceptions where development is needed for safety or would better protect biological resources and natural topography; public trails are exempt. § 22.44.1350

On property containing slopes of 15% or more, site and grading design must preserve topography and vegetation, mimic natural contours, reduce the scale of cut-and-fill slopes and retaining walls, and protect scenic views and trails. § 22.44.1350

Drainage is a core hillside issue. Roof drainage must be directed to a retention basin or collector system, runoff should be conveyed safely to natural drainages, and artificial outlets may not discharge onto slopes. § 22.44.1350

The cited sources do not establish a universal HMA grading-volume threshold. A separate Community Standards District may impose its own threshold or permit process; verify applicable overlay districts and local standards rather than assuming that a rule from another community applies.

Landscaping and Scenic Integration

Landscaping is a functional hillside-control measure, not merely decoration. The Guidelines and hillside standards emphasize locally indigenous, drought-tolerant vegetation for restoration, terraced slopes, erosion control, and visual integration. §§ 22.104.070, 22.44.1350

Terrace drains in cut-and-fill slopes must use colored concrete that blends with natural soil or be concealed by berms. Terraced graded slopes must be landscaped with locally indigenous plants of varied type, density, and form. § 22.44.1350

New water tanks visible from scenic roads or public viewing areas should be partially below grade where feasible; visible portions must use landscape-compatible colors, and screening may be required in high-scenic-value areas. § 22.44.1350 For broader planting and screening obligations, see landscaping and screening.

Density, Uses, and Related Standards

Chapter 22.104 does not increase or reduce the maximum number of dwellings by itself. The applicable area, community, neighborhood, or specific plan determines maximum density or intensity; without such a plan, the Land Use Element methodology governs. § 22.104.010

Actual constraints on yield can still be substantial. The Guidelines identify land-division rules, minimum lot size, lot width, frontage, access, zoning setbacks and lot coverage, habitat, geologic and fire hazards, open space, utilities, easements, and parking as factors that may affect the feasible density of a hillside proposal. § 22.104.070

The chapter does not supply a distinct HMA rule for ADUs. Whether an accessory dwelling unit is allowed, and how state housing rules interact with the site, is not found in source materials; verify with the jurisdiction and applicable California law.

County and Special-District Development

For development by the County or a special district, the lead department or district must prepare a written report documenting substantial compliance with the Hillside Design Guidelines. The report becomes part of publicly available project documents and subsequent reports to the Board and its commissions. § 22.104.070

That reporting requirement does not apply to maintenance or operations activities, or to activities identified as exempt in § 22.104.030.I; the content of those exempt activities is not found in source materials.

Checklist

• Confirm the parcel is in unincorporated Los Angeles County and verify whether an HM designation or HMA condition applies.
• Prepare a natural-slope and topography analysis showing whether slopes reach 25% and identifying slopes of 50% or greater. §§ 22.104.070, 22.44.1350
• Identify the underlying zone and applicable plan because Chapter 22.104 does not establish permitted uses, density, or intensity. § 22.104.010
• Site buildings, pads, streets, and driveways to minimize grading, protect natural landform, and retain indigenous vegetation. § 22.44.1350
• Incorporate feasible measures across site planning, grading/facilities, circulation, building design, and landscaping to demonstrate substantial guideline compliance. § 22.104.070
• Design roof and site drainage to avoid slope discharge, erosion, and instability. § 22.44.1350
• Specify locally indigenous, drought-tolerant planting for restored or terraced hillside areas. § 22.44.1350
• Evaluate whether slopes, soils, habitat, views, fire access, utilities, easements, and parking reduce the otherwise planned development yield. § 22.104.070
• Confirm grading, construction, and fire-protection requirements under the applicable California Building Standards Code and County requirements. Not found in source materials for a complete HMA building-permit standard.

Risks & Ambiguities

Plain-English Summary

If your unincorporated Los Angeles County parcel has 25%+ natural slopes, plan the project around the hillside instead of flattening the hillside around the project. The County expects a site-specific design that limits grading, protects vegetation and views, manages runoff safely, and fits the natural contours; your underlying zone and plan—not the HMA chapter—determine what use and density may be allowed. §§ 22.104.010, 22.104.070, 22.44.1350

Source References

• Los Angeles County Zoning Code, § 22.104.010 — purpose; density and intensity.
• Los Angeles County Zoning Code, § 22.104.020 — Chapter 22.104 definitions cross-reference.
• Los Angeles County Zoning Code, § 22.104.070 — County/special-district development and Hillside Design Guidelines.
• Los Angeles County Zoning Code, § 22.06.050 — HM as Hillside Management Special Management Area.
• Los Angeles County Zoning Code, § 22.44.1350 — hillside management development, grading, drainage, and landscaping standards.
• Los Angeles County Zoning Code, § 22.46.490 — cited slope landscaping, irrigation, and development standards.
• Los Angeles County Planning Code, § 21.08.160 — definition of sloping terrain.