Wednesday, December 15, 2021
"There is no playbook for an emergency like this one," said a county supervisor.
A significant landslide in Rancho Palos Verdes, California, has prompted evacuation warnings for approximately 100 homes in the Portuguese Bend neighborhood. The landslide, which has been worsening over the weekend, covers an area of 680 acres and has caused damage to homes, roads, and infrastructure. Southern California Edison has shut off power to 140 homes due to safety concerns, with additional residents at risk of losing electricity.
Local officials are urging residents to evacuate and have indicated that the county is committed to responding with $5 million in aid. There are calls for state and federal assistance as the situation escalates, with concerns about leaks from water and gas pipes potentially making some homes uninhabitable.
Landslides in Rancho Palos Verdes, California, are a recurring issue due to the area's geology and climate. The area has experienced landslides for thousands of years, with the most recent significant activity beginning in 1956. The Portuguese Bend Landslide (PBL), which is part of a larger landslide complex, has been continuously moving since its reactivation in 1956.
The PBL is characterized by slow but continuous movement. The rate of movement varies, but it has been estimated to be around three feet per year. However, this rate can increase significantly after periods of high rainfall, reaching up to 1.5 inches per day.
In recent years, the landslides have become more frequent and severe, particularly after substantial rainfall. For example, as of 2024, the area has seen increased land movement, with some areas moving about a foot per week due to trapped water from earlier rainfall. The landslides are influenced by the local geology, including the presence of seaward-dipping strata and the sheared bentonite clay bed that serves as the basal rupture surface for the PBL. Groundwater levels also play a crucial role in destabilizing the slopes.
The landslides have significant impacts on infrastructure and residential areas, leading to damage and displacement. Efforts to mitigate the landslides include drilling to add drains and pumps to reduce groundwater pressure, but these measures have had limited success in stopping the movement entirely.
Landslides can pose several hazards, including:
1. Property Damage: Landslides can destroy homes, local infrastructures, and roads, leading to significant economic utility losses.
2. Injury and Fatalities: The sudden nature of landslides can result in injuries or fatalities to people in the affected vicinity.
3. Displacement: Communities may be forced to evacuate or permanently relocate due to substantial unsafe conditions.
4. Environmental Impact: Landslides can disrupt ecosystems, destroy animal and human habitats, and lead to soil erosion.
5. Water Quality Issues: They can contaminate water sources with debris and pollutants. So, be sure to check for a boil water warning or warnings to not use tap water.
6. Infrastructure Disruption: Landslides can block roads, railways, and waterways, hindering transportation and emergency services.
7. Secondary Hazards: They may trigger other hazards, such as floods or tsunamis, especially in coastal areas.
Mudslides: Planning and Being Prepared
Water Purification for Preppers: A Comprehensive Guide
