The dirt on a steep slope tends to slide or erode when normal rainfall runs down it, and heavy rain causes serious and potentially dangerous mudslides. Adding the right reinforcements keeps the dirt on the slope. Some slope reinforcement options don't look very appealing, but other ideas use landscaping techniques that can make your steep slope both safe and attractive.
Low Ground Covers
Planting grass will stabilise the surface of the steep slope if you make the seed stick until it sprouts, but keeping this vegetation trimmed and neat is impossible on a steep slope. Try planting low-height ground cover plants instead, recommends the United States Department of Agriculture (USDA). These plants spread shallow roots that keep the soil on the slope in place, but they keep themselves short and neat without mowing. Evergreen plants such as short, spreading varieties of juniper also cover up the bare soil year-round.
Building a short wall at the base of the slope, also known as a retaining wall or a toe wall, prevents the soil that does slide down from moving too far, says Donald Gray in his book "Biotechnical and Soil Bioengineering Slope Stabilization." This is especially important if your home or other structure is near the base of the slope where moving soil could damage it. The wall must be able to withstand the high weight and pressure of wet soil, so a simple stacked rock wall won't be enough for a tall and steep slope.
Water naturally runs down a steep slope in even the driest conditions when rain falls. As soil absorbs moisture, it becomes heavier, and slowly slides or washes down the grade. Installing carefully planned draining ditches or even buried drainpipes routes water where it will do the least damage to the face of the slope. Add a ditch at the top of the slope and connect it to the drains running down the slope. This will divert water that would otherwise run straight over the edge.
Cutting flat sections into a slope is known as terracing, and this landscaping project makes the slope usable as well as stable. Many farmers in countries with steep but fertile mountainsides cut growing fields directly into the slopes. You'll need to consult a landscaping engineer before you begin a terracing project, warns the USDA, because an improperly designed terrace is more dangerous than an unsecured slope, no matter how steep it is. Terraces need support along the edges of each step to prevent collapse and large-scale soil sliding.