Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study identifies California cliffs at risk of collapse

21.12.2017

Danger - Unstable Cliffs - Stay Back: The yellow warning signs that pepper coastal cliffs from northern California to the US-Mexico border may seem overly dramatic to the casual observer. But actively eroding cliffs make up the majority of the California coastline, and sudden landslides and collapses have caused injuries and several fatalities in recent years. In addition, eroding cliffs currently threaten highways, houses, businesses, military bases, parks, power plants, and other critical facilities--all in all billions of dollars of development.

Research suggests that erosion rates will increase as sea level rises, further exacerbating these problems. "It is critical we study current and historical cliff retreat so we can better plan for the future," says Adam Young, a researcher at Scripps Institution of Oceanography at the University of California San Diego who recently published a unique large-scale analysis of coastal cliff erosion in California.


Adam Young, a researcher at Scripps Institution of Oceanography at the University of California, San Diego, recently published a new large-scale analysis of coastal cliff erosion from San Diego to San Francisco. To analyze the data, Young compared two massive LiDAR data sets, three-dimensional maps of the California coastline, recorded eleven years apart. This video highlights one of the areas he identified with high erosion rates, near San Francisco.

Credit: Adam Young, Scripps Institution of Oceanography, University of California San Diego

The study, published in the journal Geomorphology, and funded by California Sea Grant, provides accurate erosion rates for 680 miles of the California coast, from the US-Mexico border to Bodega Head in Sonoma County.

It identifies areas that have eroded faster than others, and introduces a new experimental hazard scale to identify areas that may be at greater risk of impending collapse. It is the first such large-scale study in California using LiDAR data--laser elevation data recorded in aerial surveys--which were used to create detailed 3D elevation maps.

... more about:
»clear »erosion rates »rainfall »sea level »waves

Existing cliff erosion studies are often small scale, use a variety of techniques, and often rely on lower quality data sources, providing a patchwork across the state. "What's unique about this study is that it applies a consistent methodology across a very large area using accurate high-resolution laser data," says Young.

While some of the basic causes of coastal cliff erosion--such as rainfall and waves--are clear, this has not translated into a simple way to predict future erosion rates or identify areas at risk. Variation in cliff geology, beach protection, exposure to weather, and other factors also complicate predicting erosion rates.

Previous research has identified clear correlations between rainfall and coastal erosion in southern California, but the impact of storms waves has been more elusive. "It's difficult to measure," explains Young, "We lack field observations because with powerful waves crashing against the cliff, it is not an easy place to make measurements." Variation in cliff geology, beach protection, exposure to weather, and other factors also complicate predicting erosion rates.

Understanding erosion, preventing disaster

To create a consistent analysis of recent cliff changes, Young compared two massive LiDAR data sets, three-dimensional maps of the California coastline, recorded eleven years apart. The highest cliff erosion rates were found in San Onofre, Portuguese Bend, Palos Verdes, Big Sur, Martins Beach, Daly City, Double Point, and Point Reyes (see map). Young then compared the recent cliff erosion maps to historical records from 1932 and 1934. By comparing the different maps, he built an analysis for the majority of the state's coastline, showing both recent and historical erosion rates.

The study shows that the historical cliff erosion rate does not always provide a good prediction of future rates. "The results show that if a cliff experienced a large of amount of erosion during one time period, it was followed by a time period with very little erosion, and the cliff could be relatively stabilized for a time," explains Young. "It will mobilize again, but we don't know when and more research is needed to better understand the time cycles involved."

Young also found that cliffs with high erosion rates in recent times were often preceded by time periods with very little erosion. These are key findings, because models predicting future cliff retreat are often based on projecting the historical rates.

Young also introduced a new experimental measure to identify the riskiest precipices. Previous research had suggested that the difference between erosion rates of the cliff face compared to the cliff top could indicate instability--in short, the cliff steepness. When he applied this hazard index, Young identified worrisome spots along the California coast, including San Onofre State Beach, Big Sur, Martin's Beach, and Daly City.

A reality check for planners

Young is currently working on a set of maps to be made available to the public, and he has presented the work at scientific conferences. He says, "I hope that this study will help improve models that predict erosion, help identify hazardous areas, and assist policymakers who are working to protect our coast."

The research has already caught the attention of planners at the California Coastal Commission, a state agency charged with preserving and protecting the coastline for current and future generations.

"The study could be particularly useful for local governments looking to update their local coastal programs in light of climate change and sea level rise," says Lesley Ewing, a senior coastal engineer for the commission. While the study does not provide projections for future erosion rates, researchers expect that sea-level rise will contribute to faster erosion rates and greater risk to public and private coastal property, and governments are working to plan for the impacts.

"The coast of California is stacked with very expensive real estate--not to mention power plants, wastewater treatment facilities, and highways," she says. Some of this is already at risk--over 100 miles of shoreline armory has been built to protect it, and more will be at risk in the future.

"There's so much opportunity to use this research--this could serve as a reality check for planners who often focus on specific regions and smaller scales," adds Ewing.

###

The research was also supported by the California Department of Parks and Recreation, Division of Boating and Waterways.

About California Sea Grant

NOAA's California Sea Grant College Program funds marine research, education and outreach throughout California. Our headquarters is at Scripps Institution of Oceanography, University of California, San Diego; we are one of 33 Sea Grant programs in the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.

Media Contact

Katherine Leitzell
kleitzell@ucsd.edu
858-346-3665

 @UCSanDiego

http://www.ucsd.edu 

Katherine Leitzell | EurekAlert!

Further reports about: clear erosion rates rainfall sea level waves

More articles from Earth Sciences:

nachricht World’s oldest known oxygen oasis discovered
18.01.2018 | Eberhard Karls Universität Tübingen

nachricht A close-up look at an uncommon underwater eruption
11.01.2018 | Woods Hole Oceanographic Institution

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>