Now that we have an El Nino rainy season bearing down upon us, we now switch from worrying about water conservation to worrying about keeping our slopes from sliding down hill under the onslaught of heavy rains that supersaturate the soil. The strategies for doing this are several fold:
EVALUATE the current slope conditions. It is not uncommon that homeowners in their worrying about fire hazards have eliminated all the native woody brush on the slopes around their house. However, on steep slopes the removal of the chaparral can often destabilize the slope with the removal of these deep root systems that have kept them stable.
PREVENT water runoff from concentrating on slopes and causing severe erosion or slope failure. For now, this might have to be with heavy duty plastic sheeting with sandbags tied to ropes that hold the sheeting down. It also might mean diverting water away from slopes wherever possible. Especially roof runoff should be kept from going down hillsides. Sometimes this can involve sump pumps if there is not positive drainage to the street.
INSTALL deep rooted drought tolerant plants with low fuel hazard. Slope retention near houses always involves a compromise between the need for a deep and well knit root system and the minimizing of potential fuel for the reduction of potential fire hazard. Certain succulents make excellent choices for this kind of situation, being both deep rooting, very low maintenance and drought tolerant. But Ice Plants of all kinds are not the answer as they have very weak roots and pull out easily in saturated soils.
EXAMINE trees that might be top heavy and fall over in torrential rains. It is very common to see large trees fall down over houses in heavy rains because the weight of rainwater on the branches plus winds creates a double whammy for taking them down. Such trees should most likely be cut back and/or cabled to prevent property damage.
INSTALL retaining walls only where absolutely needed. Because they are expensive, retaining walls should be placed only where there is no other solution. There are many types available; the most versatile and attractive for slopes are the plantable walls of Verdurastone (see www.soilretention.com ).
Pasadena, Altadena, South Pasadena, Sierra Madre,
San Marino, Arcadia, CA