Wednesday, June 12, 2024

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The LaVerkin Bench in Utah has experienced destructive landslides.


Google Street View image of the landslide at LaVerkin Bench in Utah.

Dave Petley, an expert in landslide research and management, is the author of The Landslide Blog.

Image of a landslide partially covered with a transparent sand-colored overlay and the words “The Landslide Blog,” centered, in white

In LaVerkin, Utah, USA, a number of destructive landslides are causing significant damage to residential homes. The slope failures are taking place on a steep bluff located on 560 West street, on the outskirts of the city. As of now, two houses have been completely destroyed, and another was forced to evacuate last week. A thorough view on Google Street View clearly depicts the problem.

Google Street View image of the landslide at LaVerkin Bench in Utah.

A photo from Google Street View showing the landslide that occurred at LaVerkin Bench in Utah.

St George News has a good article about this interesting case study. The landslides are located at [37.20705, -113.28223]. Google Earth has good time series imagery that shows the evolution of the situation well. Initial issues were noted as long ago as 2005, when same damage was done to the land around one of the properties. The image below shows the situation in 2011, including the steep bluffs of the LaVerkin Bench and the houses at the top:-

Google Earth image of the LaVerkin Bench in July 2011.

In July 2011, a Google Earth photo of the LaVerkin Bench was captured.

In May 2013, there was a significant decline in the situation as a substantial slope failure began to erode the edge of two properties.

Google Earth image of the LaVerkin Bench in May 2013, showing the developmemt of a substantial landslide on the left side of the slope as shown in the image.

In May 2013, a Google Earth image captured the LaVerkin Bench, revealing a significant landslide forming on the left side of the slope.

In April 2021, a different section of the incline had become highly active, resulting in the demolition of two properties.

Google Earth image of the LaVerkin Bench in April 2021, showing the development of a second area of landsliding on the right side of the slope as shown in the image. Two houses had been demolished.

In the image from April 2021 on Google Earth, the LaVerkin Bench can be seen with a new area of landsliding on the right side of the slope. The image also reveals the demolition of two houses.

The latest picture, dated May 2023, depicts a significant expansion of the landsliding zone.

Google Earth image of the LaVerkin Bench in May 2023, showing enlargement of the areas of landsliding.

In May 2023, an enlargement of the landsliding areas can be seen in the Google Earth image of the LaVerkin Bench.

In January 2021, the city council requested a geotechnical report for the site. The report’s main findings are twofold. Firstly, the geology consists of impermeable basalts covered by permeable stream flow deposits, with some artificial fill. This is a common condition for a perched water table in unstable materials, which can lead to slope failures. Secondly, the primary source of water causing the landslides is believed to be the infiltration of unused irrigation water from the surrounding fields and lawns on LaVerkin Bench. The report states that this contribution is four times greater than that of precipitation.

The report proposes implementing a drainage system to intercept excess groundwater as the initial form of mitigation, but I have reservations about the potential cost.

The situation is devastating for homeowners. Unfortunately, insurance policies in the USA (and in many other countries) do not provide coverage for this type of situation, leaving the property owners responsible for all costs. A Gofundme campaign has been created to offer support, but it has only received a modest amount of donations.

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