It's Raining - It's Pouring : Protect Your Landscape from Excessive Rain
Hooray – the sun is back again! And perhaps the drought cycle is broken now! Pictures on the news were showing the effects of the recent deluges, and some of them were quite dramatic. Stepping into a puddle outside the front door is annoying but nothing compared to the destruction that water can wreak when not channeled properly. Some of the damage that a deluge can create in our landscapes is beyond our control, such as rising rivers or breaking dams. But rain water washing out driveways, entering patios or – heaven forbid - eroding your slopes can be guarded against.
Here are some vital strategies:
Most homes are constructed with drainage in mind, but you should make sure that the landscaping slopes away from your home so that excess water can flow away from it (research the guidelines that may differ depending on surface material). Drainage intakes, grates, swales, trenches, and ditches should be clear and free of any obstructions; so should gutters and downspouts, making sure they channel water down, out and away from your property. You’d be surprised at how much water damage could be averted by simply having fully functional gutters.
Raised Beds, Berms, Trenches, Soil Amendments
When your soil is clayish, it will hold onto water longer, and each additional rain shower will take time to drain away. “Soil prep” (amending your soil with organic matter or sand) to possibly as 6-12 inches deep will increase the clay’s absorption rate and prevent from water clogging the soil pores, thus providing air to the plant roots.
If soil amendments are not possible everywhere and occasional flooding can’t be avoided, you can move plants onto higher ground, either by putting them in containers, raised beds or berms. “Berming up”, i.e. creating artificial mounds will aid in keeping your plants on the dryer side. Incidentally, creating an undulating landscape with raised areas will make your landscape more visually interesting.Additionally, creating trenches for the surplus water might be needed to direct the water away from the garden.
Re-direct Stormwater Runoff
Swales, French Drains, Catch Basins, Channel DrainsFiltering the stormwater runoff before it moves downhill is advantageous to neighbor properties and the health of rivers and streams. To do this, create broad, shallow swales. If water is moving at a faster speed and erosion is a problem, install a French drain below the surface.Consider installing channel drains in patios and driveways to properly handle any water buildup that may occur. Channel drains are installed within the concrete itself, with access vents to catch the water before it presents a threat.
Reduce Impermeable Surfaces
A good deal of the water in our gardens can be traced to impermeable surfaces. “The next time it rains.. trace the water flowing along ditches and gutters back to the points where it leaves your yard. Chances are, it’s cascading off of a solid surface, like a roof or driveway, which prevents rain from soaking into the ground. [These] “impermeable surfaces” are a major cause of storm water runoff, particularly in urban areas. One way to curb runoff is to reduce the number of impermeable surfaces in your landscape. That allows water to stand long enough for the ground to absorb it. Start by taking stock of the surfaces in your landscape. Which ones are impermeable, and which of those can be replaced with a more permeable alternative? (Source: gardenclub.homedepot.com)
Protecting Newly Prepped Planter Beds
At one of my projects, the crew had just finished removing the old plants and prepping the beds with amendments. When the work needed to be stopped because of the approaching storm, here are the precautions that the contractor took to protect his work from storm damage.
Natural fibers, biodegradable fibers in erosion control
He fastened Coconut fiber coir to the edges of the newly prepped planter bed to protect it from run-off and erosion. These coirs or wattles are derived from the husks of coconuts; jute netting (not “poly jute” which is synthetic) and sisal fibers are also used to make semi-permanent netting, mats, blocks, and wattles, all with various usages in bank stabilization and erosion control. They are the strongest and most robust erosion control options available. (Note that natural-fiber netting might be environmentally preferable).
Pebbles
He also protected the drains with pebbles so that the soil, not yet protected by mulch and plants, would not get clogged up.
Slopes
Slopes can cause the greatest anxiety because if unstable they can cause major damage to your home and landscape. The appropriate plants, proper mulching, and the right irrigation system have the greatest chances of success. Unless the nature of the slope is such to requires also cross-drains, terracing and/or retaining walls. A qualified, licensed landscape contractor can help you assess the best approach to stabilizing your hillside, and in more serious cases I’d call upon the expertise of a geotechnical engineer and/or hydraulics engineer.
Irrigation Systems and Slopes
Of course, the wrong irrigation system on your slope can make all this work worthless. Rotors that apply water “fast and furiously” will throw water on the slope that will run off before it can soak into the plant roots. Also, a water jet that hits plant foliage rather than the small plants behind the obstacle will also cause run-off. In some cases, i.e. with low-growing plants, you can be successful with spray irrigation. Although drip irrigation is often the best way to apply irrigation water. Be careful not to soak the soil too deeply as this may cause more problems that no water at all.
Looking around at nature, the most successful and attractive slopes seem to be those with substantial plant life on them! This is because plant roots have soil stabilization functions, as well as softening the impact from rain, and various other benefits that plants provide here. There are numerous articles written about slope stabilization. I want to quote from one that is posted on the website of Las Pilitas Nursery, a grower of California native plants.
“Most hillsides can be made relatively stable with plants. A planting can stop nearly all erosion and hillside movement in a landscape. Almost. The only way of stabilizing a slope better than plants is a reinforced retaining wall “. Even if you don’t want to use California natives on your slope, you’ll find ideas here that you can transfer to your own slope"
Around Your House
Keep your gutters clean, and prevent clogging by installing gutter guards. Gutter guards are the device used to protect the clogging of the roof gutter so that the water from the roof may flow easily and accumulation of water does not take place on the roof but away from the house.
Turn off irrigation
Don’t forget to turn off any automatic irrigation systems until your garden has dried out to a depth of 3-4 inches on the surface. Turning it on again might not be needed until March or April. How do you know that the soil has dried out that deep? Use a soil tube! It’s one of my best tools in the gardening kit.
Water is an “un-precise element” (that’s what the engineer explained to me when I asked him about the brow ditch that the crews were building to divert water from the newly cut slope) and its force and actions not entirely predictable. We can only prepare for it as best as we know. Let’s hope for a safe rainy season and more rain – but of the gentle kind.