Olivenhain Municipal Water District’s 2020 WaterSmart Landscape Contest winner Laura Lisauskas redid her family’s street-facing sloped side yard. Photo: Olivenhain Municipal Water District

Protect Your Hillsides and Slopes 

San Diego County features many native canyons, and many homes are located in proximity to a native canyon. Native canyon hillsides near your home should not be disturbed. The more you can adapt your home’s landscaping to Nature’s landscaping, the healthier and more low maintenance it will be.

Your home may have been built on canyon slopes leveled or filled. When planting in previously disturbed or built slopes and hillsides, choose low-water use plants and trees, especially deep-rooted native plant species. Climate-appropriate plants with strong root structures are the best choices. Their powerful root systems can help hold your soil together.

Coarse compost and mulch can be applied directly to hillside and slope surfaces, providing protection from the force of rainfall and shading exposed soils, if your slope is gentle with a 33% grade or less. With occasional and gentle irrigation, mulch will “knit” together.

Compost blankets are another type of erosion control mat applied to the soil surface to protect and preserve it. They can be used alone, with coir mats or other organic-engineered material with biodegradable grids for stabilization. Mats allow water to penetrate through to the underlying soils while retaining loose soil and debris, preventing erosion. You can plant right through them, or use pre-seeded products.

Irrigation tips to help preserve hillsides

Be sure your irrigation plan takes into account hills and slopes to prevent wasting water and erosion. Photo: Pixabay

Prepping Hillside for planting

When preparing a hillside for planting, plan your irrigation before doing any work. Low-volume rotating spray heads are ideal for sloped areas, if the space is large and the groundcover is uniform. Inline emitter drip tubing can also be effective, especially for wider-spaced shrubs and trees.

Water can be applied in repeated short periods over the course of 24 hours so it can be fully absorbed between application times. Runoff, erosion, and efficient deep watering should be factored into all landscaping plans, but especially for hillsides.

NOTE: When using a drip irrigation system, emitters should be placed above the plant basin. Spray systems should have check valves in all lower heads to avoid low point runoff. Irrigation for the top of the slope and bottom of the slope should be on separate valves.

This article is part of a year-long series inspired by the 71-page Sustainable Landscapes Program guidebook. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at