Preparing Southern California Properties for El Niño: Why Stormwater Management Matters
By Larry Sheehan, ASLA, LEED AP Award-Winning Principal Landscape Architect,Verde Design Group California Landscape Architect #3180
In Southern California, we spend a lot of time talking about saving water. But responsible water management isn’t only about cutting back on irrigation. It also means being ready for the days when far too much water arrives at once.
This year, that matters more than usual. NOAA is forecasting a greater than 90% chance of a very strong El Niño during fall and winter 2026–27. El Niño doesn’t guarantee a wet winter, but it raises the odds of heavy rain, flooding, and erosion. For HOAs, multifamily communities, commercial properties, and industrial facilities across San Diego, Orange, and Riverside counties, the time to prepare is now, before the first big storm.
Why Stormwater Runoff Matters
Rain itself isn’t the problem. The trouble starts when water moves too quickly across roofs, parking lots, walkways, slopes, and compacted landscape areas without soaking in, being filtered, or being directed somewhere safe.
Along the way, runoff picks up oil, pesticides, fertilizers, chemicals, trash, and sediment. In much of Southern California, whatever enters a storm drain reaches local waterways and the ocean without treatment. That pollution hurts water quality and contributes to the beach closures we see after heavy rain.
On the property itself, poorly managed runoff shows up as flooded parking areas and building entrances, clogged or damaged drainage systems, eroded and unstable slopes, damaged planting and irrigation, sediment in streets and drains, and higher maintenance costs and liability.
The goal isn’t to get rainwater off-site as fast as possible. Whenever conditions allow, it should be slowed down, filtered, and absorbed before it leaves.
El Niño Checklist for HOAs and Commercial Properties
Start at the roof and follow the water all the way to where it leaves the property. Problems usually show up somewhere along that path.
Roofs, gutters, and downspouts
- Clean gutters and downspouts.
- Make sure downspouts don’t discharge toward buildings or onto unstable slopes.
Drains and drainage lines
- Inspect surface drains, drain inlets, and underground lines.
- Clear leaves, trash, sediment, and other obstructions.
- Note any spots where water collects near foundations, entrances, or walkways.
Slopes and brow ditches
- Clear brow ditches and drainage channels.
- Look for bare soil, erosion, failing vegetation, or exposed irrigation lines.
Basins and swales
- Inspect retention and detention basins.
- Remove dead vegetation and debris that could block water flow.
Loose materials
- Secure mulch, gravel, and other landscape materials that could wash into drains.
A word of caution on vegetated swales, drainage areas, and retention basins: the plants in them are often doing real work, slowing and filtering stormwater. Remove the dead material and obstructions, but don’tstrip out the vegetation that keeps the system working.
Long-Term Stormwater Solutions Start With Landscape Design
Cleaning drains is essential, but it’s maintenance. Long-term resilience starts with how the landscape is planned. Depending on the site, effective strategies may include:
- Deep-rooted plants that stabilize slopes
- Vegetated swales that slow and filter water
- Retention or infiltration basins and rain gardens
- Permeable paving
- Soil improvements that increase absorption
- Groundcovers that protect exposed soil
- Strategic grading and drainage improvements
- Replacing unnecessary turf with climateappropriate planting
Planting alone can’t correct every drainage issue. Soil conditions, grading, slope stability, infrastructure, and long-term maintenance have to be evaluated together, and some improvements require coordination with a civil engineer or other specialists. That’s where working with a licensed landscape architect makes a difference.
Water-Wise Landscapes Should Handle Stormwater, Too
Under California’s AB 1572, irrigation of nonfunctional turf is being phased out, starting with commercial, industrial, and institutional properties in 2028 and HOA andmultifamily common areas in 2029. When that turf comes out, the new landscape should be more than a plant substitution. It’s an opportunity to improve soil health, strengthen slopes, slow runoff, and build a more resilient site. The turf rebate programs we work with already point in this direction: they require a rainwater feature such as a bioswale, rain barrel, or dry creek bed.
Verde Design Group helps HOAs, multifamily communities, commercial properties, and industrial facilities throughout Southern California develop practical WaterWise solutions. We evaluate planting, irrigation, drainage, maintenance, and long-term performance as one connected system.
Frequently Asked Questions
Does El Niño mean a wet winter in San Diego?
Not necessarily. El Niño shifts the odds toward a wetter winter in SouthernCalifornia, but it doesn’t guarantee one. Preparing early is the lower-risk choice either way.
When should HOAs and property managers prepare for El Niño?
Before the rainy season begins, ideally in early fall. Drain cleaning, slope inspections, and basin maintenance are much easier to schedule before the first storm than after it.
Schedule Your Stormwater Assessment
Don’t wait for the first major storm to show you where your site is vulnerable. Contact Verde Design Group to schedule a WaterWise landscape and stormwater assessment.
