Mitigating Landslides Post Hurricane Helene

— Written By
en Español / em Português
Español

El inglés es el idioma de control de esta página. En la medida en que haya algún conflicto entre la traducción al inglés y la traducción, el inglés prevalece.

Al hacer clic en el enlace de traducción se activa un servicio de traducción gratuito para convertir la página al español. Al igual que con cualquier traducción por Internet, la conversión no es sensible al contexto y puede que no traduzca el texto en su significado original. NC State Extension no garantiza la exactitud del texto traducido. Por favor, tenga en cuenta que algunas aplicaciones y/o servicios pueden no funcionar como se espera cuando se traducen.


Português

Inglês é o idioma de controle desta página. Na medida que haja algum conflito entre o texto original em Inglês e a tradução, o Inglês prevalece.

Ao clicar no link de tradução, um serviço gratuito de tradução será ativado para converter a página para o Português. Como em qualquer tradução pela internet, a conversão não é sensivel ao contexto e pode não ocorrer a tradução para o significado orginal. O serviço de Extensão da Carolina do Norte (NC State Extension) não garante a exatidão do texto traduzido. Por favor, observe que algumas funções ou serviços podem não funcionar como esperado após a tradução.


English

English is the controlling language of this page. To the extent there is any conflict between the English text and the translation, English controls.

Clicking on the translation link activates a free translation service to convert the page to Spanish. As with any Internet translation, the conversion is not context-sensitive and may not translate the text to its original meaning. NC State Extension does not guarantee the accuracy of the translated text. Please note that some applications and/or services may not function as expected when translated.

Collapse ▲

Landslides

During Hurricane Helene our area was hit with almost 2000 landslides. A landslide is basically the downhill movement of soil or rock from an overly steep slope. This movement can happen slowly with the hillside quietly but inexorably moving down slope. Or, the failure can be catastrophic, sending tons and tons of rocks, soil and debris racing downhill as we saw recently during Hurricane Helene.roadside failure

Landslides and rockfalls are part of living in mountains everywhere. Did you know that these Appalachian Mountains that we live in once were the height of the Himalayan Mountains? Mount Mitchell was once as tall as Mount Everest? Where did all that material go? It was eroded away and flushed down the rivers over millions of years. The Appalachians are still eroding away, sometimes slowly, sometimes quickly but always diminishing. Big landslides are just the most visible aspect of this process.

Geologist Phillip Prince Explains Landslides

A Problem That is Usually Too Big

If you have a landslide on your property repairing it can be an extensive project and expensive. Even small landslides can cost thousands of dollars to mitigate. Larger landslides can cost hundreds of thousand to millions of dollars to repair. Most homeowners do not have that kind of money. Sometimes insurance companies will not cover repairing landslides. So, many landslides are too big for normal people to mitigate.

Repairing Smaller Landslides

When you have had a landslide or washed out driveway, the first thing to do after a disaster has been declared is to contact your home insurance company. Next, homeowners should apply for FEMA aid. Once this is done, you should repair the damage. Keep your receipts and hope that in the future some other agency can help reimburse you. However, this funding is not guaranteed so be prepared financially to cover the expenses yourself.
After a landslide area or washout has been determined to be stabile enough to enter, in some instances, homeowners or landscapers can mitigate small landslides with soil stabilization techniques, plants, soil anchors and engineered retaining walls. This article talks about stabilizing soils. The first thing to do is to cover the eroded site in grass seed (fescue/annual ryegrass mix) and cover the soil in jute erosion matting. This can help prevent further erosion while plans are being drawn up for a more permanent engineered solution.
Later you can plant trees and shrubs into the mat covered area. Plant roots can help hold soils together in the future when they mature. Carolina Native Nursery sells native plants appropriate to slopes. Live stakes can be used in wetter areas to establish plants that mitigate erosion. Unfortunately many nurseries got flooded after Hurricane Helene and lost their crops so plants may be hard to find.
Finally, retaining walls of various designs and materials may be appropriate to stabilize eroding slopes. Homeowners can build smaller retaining walls with supplies such as manufactured stones obtained from retail garden centers. However, there is a limit to the scope of a project that a home gardener can handle. If a project seems to big, get a quote from a qualified landscape contractor. Be sure to confirm with the local zoning office to see if you need a permit. Retaining walls over four feet usually require a building permit.
slope repair

Repairing Larger Landslides

Repairing large landslides is often going to be outside the abilities of someone to repair on their own. It  an be very expensive as well. Eventually, when evaluating a landslide, it will become necessary to employ an engineer. Of course there are many kinds of engineers. A structural engineer or civil engineer are likely the most helpful consultants in this case but maybe a soil engineer will be required as well. Again, check with the local zoning department to see if a building permit is required.

landslideOnce the site is evaluated and a plan is engineered, repairs can begin. Typically, robust engineered retaining walls are required. Large equipment and many truckloads of fill dirt are needed. Again, this can all be very expensive.

Government Programs Are Not Available

We are not aware of a government program that will pay for landslide repair. DOT is the only agency that might stabilize a landslide if it directly impacts a state maintained road. It seems that mostly, homeowners are responsible for repairs with possible help from insurance companies and FEMA.

Will It Happen Again?
In some cases, a slope that has failed will fail again. If you live below a slope that failed during Hurricane Helene, you should have the site evaluated by an engineer as soon as possible. The slope could fail the next time there was a big rain or it could be a hundred years before it fails again. This geologist has been analyzing landslides and clearly demonstrates that many of the areas that slid during Helene have failed in the past.
landslide and flooded condo
Hurricane Helene was a terrible event for sure. However, it is not the first time this same amount of rain has fallen on our area. In 1916 The Great Flood demolished most of the same areas. The Center for Cultural Preservation created a wonderful documentary about the 1916 flood. “COME HELL OR HIGH WATER, Remembering the Great Flood of 1916 by award-winning documentary filmmaker David Weintraub tells the story of that terrifying week in July when it seemed the world came crashing down as boulders and trees slid down the mountain, rivers became lakes, and homes were so much debris floating on the oceanic waves of the French Broad and Catawba Rivers. And finally the film highlights what lessons the Flood of 1916 has for us today.” Watch the trailer here. Although it was over 100 years since the last big flood this could easily happen again sooner than later.
landslide landslide landslide landslide landslide landslide landslide