Slope Erosion

Mike Davison, 2021

Serrano Park has far more acres of green areas per home than most communities. Much of this acreage is flood drainage channels and slopes that have been landscaped. As can be easily imagined, fighting erosion in these areas on a budget is challenging.

Long-term erosion causes soil from the slopes to be deposited near the foot of embankments. In most of our flood channels, this means the turf at the base of the embankment collects the soil and rises, creating constant sprinkler height adjustments. Along sidewalks and pathways, barriers need to be constructed to protect the path.

Along the path in the Sendero Channel, slow soil buildup in the turf across the path from the embankment, has caused a berm to form. This berm is preventing proper drainage of that area and requires that the berm is removed and the affected area re-sodded.

The sidewalk barrier along Paseo Sombra required replacing recently as the erosion became too much for the old barrier to hold back.

Slope runoff also creates ditch cleaning issues such as this drainage channel at the base of the Amapola slopes.

This is erosion buildup shortly after a rain. The grass and weeds grow very fast in the rich soil from the slopes.

Slope erosion is greatly reduced with healthy trees and shrubs to hold the slope together. The tree roots reaching into the slopes stabilize the slopes during rainy seasons to prevent mud slides. The shrubs and mulch further stabilize the slope and slow the soil erosion.

Concrete v-ditches are used to reduce erosion and slope saturation during heavy rains. These v-ditches do not work properly if there is excessive erosion along the upper slope edge of the ditch, causing the runoff to erode further and the slope to more easily saturate.

These trees on the Amapola slopes gave way during heavy rains and winds apparently due to a water saturated slope.

Most of the Serrano Park erosion issues are caused by rain and sprinkler runoff, but in some cases, we have had to deal with kids playing on the slopes with rope swings and bicycles. Repairing the damage to the slopes and the foliage is costly to the HOA, especially with its very tight budget. Only those working on the landscape should be on the slopes.

Proper irrigation also plays a role. Sprinkler irrigation does not work well for deep watering the trees and shrubs and actually encourages runoff and erosion. Drip line irrigation can deep water the drought resistant trees and shrubs optimally, encouraging deep root growth and reduced runoff. Unfortunately, the Serrano Park irrigation system is old and almost entirely sprinkler-based. The Landscape Committee is working on a long-term plan utilizing rebates and incentives to correct this but it will take time and HOA Board support.

The embankments in some areas are in need of replanting and most slopes need to be converted to drip irrigation. The Landscape Committee is working on plans to correct these and other issues but they will take time and creative funding.

We ask that the community help reduce erosion by respecting the slopes and the plants.