Landslides, also known as landslips, are the movement of rocks, debris, or earth down a slope. While certain geographic features, like hills, are more prone to landslips, various factors can initiate landslides, including rainfall, snowmelt, erosion, earthquakes, or human activities. Landslides are worsened in areas subjected to long periods of drought, as dry soil and weakened plant roots absorb less rainwater.
Many landslides occurred in California following the winter of 2022 and 2023, credited to the historic winter rainfall. Torrential rainfall set off hundreds of shallow and deep-seated landslides in over 40 counties in California. Deep-seated landslides are large-scale movements of the earth triggered over a long period of time by rain weakening the soil. These catastrophic landslides forced at least 6,000 individuals to evacuate from their homes and caused power outages for at least 200,000 homes and businesses.
Damage from landslides was also reported on June 5, 2023, impacting a set of tracks near San Clemente and San Juan Capistrano. The earth from a nearby hill where the landslide was initiated physically obstructed the railway. This strip of railway is part of the LOSSAN Corridor, which stands for Los Angeles, San Diego, and San Luis Obispo, its three major connecting cities. As the second busiest intercity passenger rail corridor in the U.S., the LOSSAN Corridor operates more than 150 daily passenger trains in 41 stations along six Californian counties.
Though the landslide in the railway tracks of San Clemente was caused by the loosening of the earth by rain, this was not the only occurrence of this section of the railway corridor being affected by landslides. This set of tracks experienced a landslide in April 27, 2023, before the second landslide on June 5, 2023.
The physical location of the railway contributes to the recurrence of landslides on the San Clemente tracks. The original construction of the railways did not account for the physical integrity of the surrounding landscape, where landslides are prone. The part of the railway affected is situated next to a large dirt hill, composed of sand and clay, which is unstable in the presence of heavy rainfall.
The proximity of the railway to the coastline also produces dangers unrelated to landslides. Rising sea levels and accelerating coastal erosion from natural and human activity threaten the safety of railways and coastal access.
The shifting landscape poses a significant danger to railways as it can physically obscure the tracks or warp the railway tracks to make them unable to be used. When small landslides occur, it can take a few hours up to a few days to fix any damage to the tracks and the landscape around the railway. Usually, the railways are paused during this time so construction can happen safely. The LOSSAN railway closed operations in the surrounding area of San Clemente for a month each for the landslides in April and June. Surrounding attractions such as the Casa Romantica Culture Center and Garden also closed at this time.
The recurring landslides and corresponding damage, with high repair costs and long periods of paused operation, are caused by poor planning. With the unpredictability of weather and increasingly severe weather patterns, future landslides are most likely to occur. In addition, there is a relatively small drainage system that does not anticipate high levels of rainfall, like the one we saw earlier this year. While building the railway close to the sea provides a scenic option that may appeal to many passengers, it is no longer a physically sound option given the common nature of the changing terrain.
The city of San Clemente recently implemented short-term solutions to the infrastructural problems on the railways. The city constructed retaining walls, also known as soil nail walls, to prevent further soil creeping onto the tracks. These walls, between 250 feet and 300 feet long and 12 to 15 feet high, serve as a barrier between the tracks and the encroaching earth. The section of the railway under repair was closed for a month while it underwent construction.
The city of San Clemente originally presented a plan of long-term construction on the hillside, by entirely removing the mound of dirt from the area. However, completely removing the hill may create more issues because this means that further coastal erosion will impact the area.
To provide a long-term solution to avoid the effects of landslides and coastal erosion, a plan to move the San Clemente railway to an inland location should be implemented.
OCTA has yet to approach such plans, but the San Diego Association of Governments shows the feasibility of relocation with their plan to relocate a 5-mile stretch of railway on the San Diego beach more inward. This plan of relocation, committed to be finished by 2035, is currently projected to cost $3 billion, but many argue that this outweighs the alternative of leaving a railway in a vulnerable position near the coastline. OCTA should adopt a similar plan to relocate the railway, as short-term solutions like the retaining walls cannot be relied on for longer periods of time.