Start before October, not after the forecast
Los Angeles gets most of its rain in a handful of storms, and those storms land on ground that has been baking since April. Bare slopes, decomposed granite, and any hillside touched by fire shed water instead of absorbing it, which is how a dry canyon lot becomes a mud problem in one night. The work that prevents it is cheap, low-skill, and has to be done before the first storm — not during it. This guide covers what to install, in what order, and what we stock for it.
The practical deadline for slope work in Southern California is the end of September. Straw wattles need to be staked into soil you can still drive a stake into; seed and blanket need a few weeks to knit; and once the first storm hits, every supplier in the county sells out of the same three items in about forty-eight hours.
It is also a permit issue on active sites. Graded lots in Los Angeles typically carry an erosion-control condition that requires measures in place during the wet season, and inspectors do check. Doing it in August is a scheduling decision; doing it in December is an emergency.
How the measures stack up
Erosion control works in layers: slow the water down, hold the soil in place, and catch what still gets away. One product rarely does all three, which is why hillside jobs use two or three of these together.
| Measure |
Job |
Best On |
Limit |
| Straw wattle |
Slows sheet flow |
Long open slopes |
Needs correct spacing |
| Erosion blanket |
Holds surface soil |
Newly seeded ground |
Covers small areas |
| Woven fabric |
Filters sediment |
Downslope edges |
Needs stakes, trenching |
| Flood barrier |
Diverts running water |
Doors and driveways |
Not for slope faces |
The spacing question in that first row is the one people get wrong. On a gentle slope, wattles can sit far apart; as the grade steepens, the rows have to come closer together, because the goal is to interrupt water before it gains enough speed to cut a rill. When in doubt, closer is better and cheaper than repairing a gully.
Straw wattles: the workhorse of the LA hillside
A straw wattle is a tube of compressed rice straw in a net casing that you lay across the slope, on contour, and stake down. Water hits it, slows, drops its sediment, and soaks in instead of running. Our 8 in. x 25 ft. rice straw wattle is the standard size for residential slopes and post-fire lots.
Two installation details decide whether it works. First, follow the contour — a wattle laid at an angle channels water sideways to the low end and concentrates the problem instead of spreading it. Second, seat it into a shallow trench so the tube contacts soil along its whole length; a wattle bridging a dip lets water run underneath and does nothing at all.
Stake it properly and it stays put. The 1 x 2 x 18 in. Douglas fir stakes suit compacted or shallow soils, and the 1 x 3 x 36 in. stakes are what you want in loose fill or where the wattle will carry real load. Drive them through the wattle at intervals along its length, and overlap the ends of adjoining wattles rather than butting them. Our note on straw wattle application and use walks through the install.
Blankets and fabric: holding the surface
Wattles slow water crossing a slope; they do not stop the slope's own surface from moving. That is what an erosion control blanket is for. The 3 ft. x 24 ft. straw fiber blanket lies directly on graded, seeded soil, keeps raindrop impact off the surface, holds moisture in while seed germinates, and breaks down as the planting takes over. On a re-seeded slope it is the difference between a lawn and a washout.
Woven polypropylene serves a different purpose. The 6 ft. x 100 ft. woven landscape fabric is dense enough to work as a sediment filter at a property line or the downslope edge of a graded pad — the same principle as a silt fence, with the fabric trenched in at the bottom edge and supported by stakes so water passes through while soil does not. It also runs as conventional ground cover under gravel, and lighter options like the 4 ft. matrix grid fabric and the 6 ft. flat bond fabric cover those beds.
Anything laid flat needs pinning or it will lift in the first wind. 3.5 in. garden staples in a 75-pack are the cheapest insurance on the job. The full range sits in our flood barriers and erosion control collection.
Protecting the structure, not just the slope
Slope measures keep soil on the hill. They do not stop water that has already reached a driveway or a garage door, and in LA the damage claim is usually the garage, not the hillside. A water-activated flood barrier stores flat and swells when wet, which makes it far easier to keep on hand than sandbags for a house that floods once every few winters.
Think about where the water goes after it leaves the slope. Downspouts discharging onto a hillside undo everything above them, and hardscape decides whether runoff spreads or channels — our guides to concrete pavers for LA hardscapes and railroad ties for landscaping and erosion control cover the built side of that. For terracing a steep yard, a low retaining wall built with the right mix — see mortar types for LA masonry — turns one long slope into two short ones, which is the most durable erosion control there is. Any wood in contact with soil should be pressure-treated.
A working sequence for a residential slope
Order matters, because each step depends on the one before it. Clear and rough-grade first, so water is not being directed anywhere you do not intend. Seed next, while the soil is still receptive. Lay blanket over the seeded areas and pin it. Run wattles on contour across the open face, staked and trenched, with spacing tightened as the grade steepens. Trench woven fabric in at the downslope perimeter to catch what still escapes. Keep flood barriers stored dry near the openings they protect.
Then walk it after the first storm. Erosion control is not install-and-forget: the first real rain shows you where water actually goes, which is never exactly where you thought. Repair undermined wattles, re-pin lifted blanket, and clear sediment from behind the fabric before the next storm arrives.
We deliver erosion control materials across Los Angeles County, and stock moves fast once the forecast turns. Ordering in late summer is the difference between having what you planned for and taking what is left.
Frequently asked questions
When should I install erosion control in Los Angeles?
Before the end of September in most years. Materials need to be staked into workable soil and seeded areas need time to establish, and supply tightens sharply once the first storm is forecast.
How far apart should straw wattles be spaced?
Closer together as the slope gets steeper. The aim is to interrupt water before it accelerates enough to cut a rill, so a steep face needs more rows than a gentle one. Where a permit or erosion-control plan specifies spacing, follow the plan.
Do straw wattles need to be removed later?
Rice straw wattles are designed to break down in place as vegetation establishes, so they generally do not need removal. The stakes and any synthetic netting are worth collecting once the slope has knitted.
Is landscape fabric the same as silt fence?
Not identical, but woven polypropylene fabric performs the same filtering job when it is trenched in at the bottom edge and supported by stakes. Lighter non-woven weed barriers are ground cover, not sediment control.
What can I use instead of sandbags?
Water-activated flood barriers store flat and dry, swell on contact with water, and are far easier to keep on hand than sand. They protect openings — doors, garages, driveways — rather than slope faces.
Does a burned hillside need different treatment?
Post-fire slopes shed water dramatically more than unburned ground because the soil surface becomes water-repellent, so measures need to be denser and installed sooner. On a burned slope above a structure, get a professional assessment rather than relying on a standard residential layout.
