Featured Research

from universities, journals, and other organizations

Historic Records Reveal Links Between El Nino, Coastal Erosion, And Shifting Sands Of Beaches In Central California

Date:
December 28, 2000
Source:
University Of California, Santa Cruz
Summary:
Erosion of seacliffs, damage to coastal structures, and the comings and goings of beach sand along California's central coast are all closely linked to the intense winter storms associated with El Niño. Two new studies by researchers at the University of California, Santa Cruz, reveal the connections between this climatic heavy hitter and the processes that shape the coastline of California.

SAN FRANCISCO, CA--Erosion of seacliffs, damage to coastal structures, and the comings and goings of beach sand along California's central coast are all closely linked to the intense winter storms associated with El Niño. Two new studies by researchers at the University of California, Santa Cruz, reveal the connections between this climatic heavy hitter and the processes that shape the coastline of California.

UCSC postdoctoral researcher Curt Storlazzi and professor of Earth sciences Gary Griggs found that damaging coastal storms are three times more likely to occur during an El Niño winter than in other years. As global warming causes sea levels to rise, storm damage on the coast will only get worse, Griggs said.

"By concentrating our population on the coasts, we have put the bulk of our civilization within a few feet of sea level," he said. "When you combine rising sea levels with El Niño on the West Coast and hurricanes on the East Coast, the result will be larger and more frequent losses due to storm damage."

In a related study, Griggs and graduate student Cope Willis found that although winter storms during El Niño can erode beaches down to bare rock, the same storms ultimately replenish the beaches by washing tons of fresh sediment from rivers and streams into coastal waters. Their preliminary results show no long-term changes in the amount of sand on central California beaches.

The studies, which involved analyses of historic records as far back as 1910, were presented December 16 and 17 at the fall meeting of the American Geophysical Union in San Francisco.

El Niño is a disruption of oceanic and atmospheric circulation patterns spawned at irregular intervals in tropical waters. It involves weakening of the trade winds and unusually warm surface waters in the eastern Pacific, leading to changes in weather in regions far from the tropics. Storlazzi used weather and oceanographic records to identify El Niño events dating back to 1910. He then ranked their intensity to create an index showing six higher intensity and 17 lower intensity El Niños in the past 90 years.

El Niño winters batter the coast harder than usual for several reasons. In a normal year, there might be one really big storm, but beaches absorb most of its force, Storlazzi said. During an El Niño year, a succession of big storms removes the protective beaches. Waves attack structures built on the beach and start hitting the seacliffs. Storms and waves also approach the coast from a more southerly direction, hitting areas normally protected from wave action. In addition, El Niño storms bring high rainfall (which saturates and weakens coastal bluffs), elevated sea levels (causing waves to break closer to shore), and bigger waves.

But not all El Niños are created equal. Storlazzi looked at equatorial conditions such as sea-surface temperature, barometric pressure, winds, and storm records to rate the intensity of El Niños, and compared those findings with conditions in California.

"With increasing El Niño intensity, there is an exponential increase in the factors that enhance coastal erosion in California, such as rainfall, wave height, and sea level," Storlazzi said. "We found that 75 percent of the shoreline erosion and damage has occurred during El Niño winters, and the moderate- to high-intensity El Niños do most of the damage."

The most recent ones, in 1982-83 and 1997-98, were among the most intense El Niños of the past 90 years, Storlazzi noted. Unfortunately for coastal dwellers, a 30-year gap between major El Niños, from 1941 to 1972, coincided with a period of intense coastal development. The result, said Storlazzi, is that a lot of people built houses in vulnerable places, such as right on the beach or on seacliffs that are now crumbling.

Beach erosion caused by the El Niño winters of 1982-83 and 1997-98 spurred calls for state-funded beach-nourishment projects. Few studies, however, have documented long-term trends in beach size or identified sites that could benefit from such projects, according to Griggs.

"There has been a big push to restore beaches in California, but before we spend millions of dollars on beach nourishment projects it's critical that we know which beaches, if any, are undergoing long-term erosion and why," Griggs said. "We also need to ask where is all the sand going to come from, how long is it going to stay on the beach, and what are the long-term costs."

Willis is studying seven beaches between San Francisco and Monterey using aerial photographs and other historic records to document changes. At the meeting, he will present results from three state beaches in Santa Cruz County indicating no net loss of beach size in this area.

"El Niño winters cause a lot of beach erosion, but the beaches recover pretty rapidly," Willis said. "The heavy rains flush out a lot of sediment, which is crucial for maintaining beach size."

In southern California, the situation is different because of the number of dams on coastal rivers that block the transport of sediment to the coast, he said. Eroding seacliffs are also an important source of sand that gets cut off when people build seawalls. Beach nourishment is a long-term commitment because sand doesn't stay in one place but moves constantly along the coast, Griggs said. "We have to ask ourselves if beach nourishment is going to be a cost-effective long-term solution. My concern is that we're just dumping sand down a hole," he said.


Story Source:

The above story is based on materials provided by University Of California, Santa Cruz. Note: Materials may be edited for content and length.


Cite This Page:

University Of California, Santa Cruz. "Historic Records Reveal Links Between El Nino, Coastal Erosion, And Shifting Sands Of Beaches In Central California." ScienceDaily. ScienceDaily, 28 December 2000. <www.sciencedaily.com/releases/2000/12/001227082034.htm>.
University Of California, Santa Cruz. (2000, December 28). Historic Records Reveal Links Between El Nino, Coastal Erosion, And Shifting Sands Of Beaches In Central California. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2000/12/001227082034.htm
University Of California, Santa Cruz. "Historic Records Reveal Links Between El Nino, Coastal Erosion, And Shifting Sands Of Beaches In Central California." ScienceDaily. www.sciencedaily.com/releases/2000/12/001227082034.htm (accessed October 22, 2014).

Share This



More Earth & Climate News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) — He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
How Detroit's Money Woes Led To U.N.-Condemned Water Cutoffs

How Detroit's Money Woes Led To U.N.-Condemned Water Cutoffs

Newsy (Oct. 20, 2014) — The United Nations says water is a human right, but should it be free? Detroit has cut off water to residents who can't pay, and the U.N. isn't happy. Video provided by Newsy
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) — Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) — Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins