Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mathematical rule said to be widely and wrongly used to forecast future beach erosion

19.03.2004


A decades-old mathematical model is being inappropriately used in at least 26 nations to make potentially costly predictions about how shorelines will retreat in response to rising sea levels, two coastal scientists contended in the Friday, March 19, 2004, issue of the research journal Science.



"Models can be a hazard to society, and this is certainly an example of such," wrote Orrin Pilkey of Duke University’s Nicholas School of the Environment and Earth Sciences, and J. Andrew Cooper of the Coastal Research Group at the University of Ulster in Northern Ireland, in a Perspectives commentary.

The mathematical equation, called the Bruun rule, "is a ’one model fits all’ approach unsuitable in a highly complex natural environment with large spatial variations in shoreline retreat," the two authors added. "Even under ideal conditions ... the rule has never been credibly shown to provide accurate predictions."


Pilkey, a retired geology professor who still directs Duke’s Program for the Study of Developed Shorelines, said in an interview that the rule was developed in the 1960s by Per Bruun, a Danish civil engineer who was long active in Florida beach preservation projects.

According to Pilkey, the Bruun rule stipulates that it is the slope of the "shoreface" -- the broad front of a beach extending down into the water to a depth of about 10 yards -- that controls how and how quickly a beach "erodes," meaning how it retreats landward as sea level rises.

"There is no relationship between the shoreface slope and the rate of erosion," he said. "We know that each shoreline is different, and one model cannot possibly explain every shoreface. It’s ludicrous. And yet it’s being defended by a number of people."

Their commentary also said the Bruun rule is intended "to be deployed only under a limited range of environmental circumstances (such as uniform sandy shorefaces with no rock or mud outcrops). Unfortunately, these constraints on its use are widely ignored, and it has been applied to such diverse coastal types as mud flats, rocky coasts and coral atolls.

"Even under ideal conditions, however, the rule has never been credibly shown to provide accurate predictions," the commentary added.

Two ways of predicting the retreat of shorelines are actually in "widespread practice," the authors noted. One way is the Bruun rule. The other method is to use a beach’s past behavior to "extrapolate" its future erosion trends. They asserted that extrapolation also "has problems" in that past data is incomplete, and different parts of a single beachfront may erode at different rates.

"We advocate recognition and acceptance that we cannot actually predict shoreline retreat related to sea level rise," Pilkey said, quoting from their commentary. "It’s too complex.

"What startles me is why people think they can take a mathematical equation that requires only a navigation chart and actually predict what sea level rise will do. The answer is because everybody thinks that if it’s done mathematically it’s sophisticated and state-of-the-art.

"One of the big lessons here is that sometimes intuition based on experience on a given shoreline is a lot better than a mathematical model."

Cooper consulted available information with the aid of an Internet computer search service to come up with the estimate that the Bruun rule is in use in 26 countries, Pilkey said.

Their commentary noted that much of the developed world has experienced "a four-decade rush to the shore, with concomitant beachfront development and exponentially increasing total values for beachfront, real estate, infrastructure and buildings."

This development has "unfortunately coincided with the century of accelerated global sea level rise," it added. That coincidence "means that the prediction of the future rate of shoreline retreat has become a major societal priority."

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu/

More articles from Earth Sciences:

nachricht Six-decade-old space mystery solved with shoebox-sized satellite called a CubeSat
15.12.2017 | National Science Foundation

nachricht NSF-funded researchers find that ice sheet is dynamic and has repeatedly grown and shrunk
15.12.2017 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

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

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>