By Larry Sheehan, Principal Landscape Architect, Verde Design Group Landscape Architects, Inc.
When I walk an HOA community, a public facility, or a commercial property ahead of the rainy season, I’m looking at more than whether the landscape looks tidy. I want to know what will happen when the rain starts. Where will the water go? What might block it? Which trees or slopes need a closer look?
With NOAA forecasting a very strong El Niño this winter, those questions matter more than usual. And they apply to a homeowner’s property, too. You don’t need to wait for a storm to find out where the trouble spots are.
Look Up at the Trees
A tree can look perfectly fine on a calm day and face a very different set of forces during a storm. Rain soaks the branches and foliage, wind pushes against the canopy, and saturated soil may give the roots less support. On a slope, that combination deserves particular attention.
Think of a dense canopy like a sail: the more surface the wind catches, the more force it puts on the branches and trunk. When an arborist identifies branches that should come out, selective pruning can reduce that force and improve the tree’s structure. It can also take care of dead limbs before they fall onto a road, walkway, building, or parked car.
That doesn’t mean cutting back every tree before it rains. Removing too much canopy can harm a tree. Ask a qualified arborist to assess trees near high-use areas and on slopes, and to recommend pruning based on each tree’s condition, species, and structure.
Adjust Your Irrigation Schedule Before the Rain
In San Diego, it’s easy to leave the irrigation controller on the schedule that got the landscape through a hot August or September. But as temperatures cool and rain approaches, that same schedule may be putting down more water than the plants need.
I recommend walking the property and checking the soil instead of assuming every zone needs the same adjustment. A sunny slope, a shaded planting bed, and an established lawn will each respond differently. If you have a smart controller, make sure its weather settings are working. If you have a conventional controller, review the watering days and run times yourself. I adjust my own irrigation throughout the year, sometimes monthly when the weather changes quickly.
Why does this matter before a storm? Soil that’s already wet from irrigation has less room to absorb rain. The excess can run off the property or leave roots sitting in soggy soil. Cutting unnecessary watering also lowers the water bill, which any homeowner or property manager will appreciate.
When rain comes, pause irrigation where it makes sense and keep an eye on the landscape afterward. Some established areas may need little or no supplemental water for a while; others will dry out sooner. Let the conditions on your property tell you when to turn each zone back on.
Walk the Slopes Before the First Big Storm
After the dry summer we’ve had in San Diego, it’s easy to assume the first heavy rain will soak right into a bare slope. Sometimes the opposite happens: water runs across the dry, hard surface and carries soil downhill with it.
On some stable, very dry slopes, lightly wetting the surface ahead of a forecast storm can help the first rain soak in. That means a small amount of water, applied slowly. It does not mean soaking the hillside. It’s a judgment call based on the slope’s condition, not a step for every property’s storm checklist.
If you see cracks, movement, seepage, or signs of an earlier slide, don’t add water. Have the slope evaluated first.
I also look for places where soil has already started moving. If dirt collects at the bottom of a slope after a rain, that tells you water is carrying it there.
Straw Wattles for Short-Term Erosion Control
One short-term option is a straw wattle. Picture a long roll of straw laid across the hillside, following the contour instead of running downhill. Properly installed and staked, it slows water moving over the surface and catches some of the loose soil. If dirt piles up behind it after a storm, you can see exactly where it did its job.
How many you need, and where they go, depends on the size and steepness of the slope and how water moves across it. On a large property, I’d walk the slope before recommending a layout. Wattles help with surface erosion, but they won’t fix an unstable hillside.
Think Beyond the Next Storm
Wattles can get you through the next storm. The bigger question is what will hold the slope in place over the next few years.
The answer usually includes plants suited to the site. Once established, their roots protect the soil and the planting covers ground that would otherwise be exposed to rain. The right choices depend on the slope, soil, irrigation, and any fire-safety requirements that apply.
When we planted our own slope at home in Encinitas, we used jute mesh while the plants got established. It comes in a roll, a bit like a loosely woven carpet. You secure it to the slope and plant through the openings. The mesh protects the surface while the plants grow, then gradually breaks down. Ours lasted about two to three years.
It’s a good example of why I look at both the immediate problem and the finished landscape. A temporary erosion measure buys time, but the planting plan is what carries the work forward.
Follow the Water and Clear Its Path
On larger properties, I pay close attention to drainage swales, the channels designed to carry water across or away from an area. Over a year, leaves, branches, and sediment collect in them. If a swale is blocked, water may go somewhere it was never meant to go.
The same goes for roof gutters, downspouts, landscape drains, and storm drain inlets. Check that they’re clear and working, then follow the drainage path. Where is the water supposed to end up? Is that route open? If the same spot backs up every year, clearing it again may not be enough. It may be time to look at the underlying drainage problem.
You can do this walk at an HOA, a municipal facility, an industrial site, or your own home. The scale changes, but the question stays the same: what will the water do when it gets here?
A storm-preparation plan doesn’t have to start with a major renovation. It starts with paying attention, keeping up with maintenance, and knowing which conditions call for a professional evaluation. That gives an owner or property manager a clearer picture of what to handle now and what to plan for over time.
Frequently Asked Questions
Should I turn off my sprinklers before it rains in San Diego?
Pause irrigation where it makes sense when rain is forecast, then check the soil afterward. Some zones will stay moist for a while; others, like sunny slopes, will dry out sooner.
What is a straw wattle, and does it stop erosion?
A straw wattle is a long roll of straw staked across a slope along its contour. It slows surface runoff and traps loose soil, but it’s a short-term measure. It won’t stabilize a hillside that’s actually moving.
Talk to a Landscape Architect About Your Property
Verde Design Group Landscape Architects, Inc. works with HOAs, public agencies, and commercial property teams across Southern California. If you have questions about your landscape’s slopes, drainage, planting, or irrigation, we can help you evaluate the site and identify practical next steps.
