Tag Archive: Erosion


The mountains on Oahu in the Hawaiian Islands are dissolving from within under the slow but inexorable onslaught of groundwater, researchers say.

Filed under: Climate Change, Discoveries, Earth Watch Report, Environmental, Evolution, Freak Natural and Not So Natural Phenomena, Water — 1 Comment
December 22, 2012

Earth Watch Report

 

WATER WORLD

Study: Hawaiian island slowly dissolving

by Staff Writers
Provo, Utah (UPI)


disclaimer: image is for illustration purposes only

 

Sometime in the distant future the mountainous tropical island will be reduced to a flat, low-lying island similar to Midway, scientists at Brigham Young University reported Friday.

While external erosion is the primary force that wears down mountains, that’s not the case on Oahu, they said.

“We tried to figure out how fast the island is going away and what the influence of climate is on that rate,” BYU geologist Steve Nelson said. “More material is dissolving from those islands than what is being carried off through erosion.”

That was the result from comparing groundwater against stream water to see which removed more of the total quantity of mineral material mass that disappeared from the island each year, the researchers said.

“All of the Hawaiian Islands are made of just one kind of rock,” Nelson said, referring to the volcanic composition of the islands. “The weathering rates are variable, too, because rainfall is so variable, so it’s a great natural laboratory.”

While Oahu is at present still growing, after about 1.5 million years the force of groundwater will eventually triumph and the island will begin its descent to a low-lying topography, the researchers said.

 

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A new model allows researchers to much more accurately predict coastline erosion due to rising sea levels.

Filed under: Climate Change, Crossroads News : Changes In The World Around Us And Our Place In It, Environmental, Seas / Oceans — Leave a comment
September 7, 2012

Crossroads News : Changes In The World Around Us And Our Place In It

Environmental : Climate Change -  Seas / Oceans

Coastline erosion due to rise in sea level greater than previously thought

WATER WORLD

by Roy Meijer
Delft, Holland (SPX)


Work in progress: Rosh Ranasinghe measuring on Narrabeen Beach, Sydney.

A new model allows researchers at UNESCO-IHE, TU Delft and Deltares to much more accurately predict coastline erosion due to rising sea levels. It would appear that the effects of coastline erosion as a result of rising sea-level rise in the vicinity of inlets, such as river estuaries, have until now been dramatically underestimated. The scientists have published their research in the online edition of Nature Climate Change.

The anticipated rise in sea levels due to climate change will result in coastlines receding worldwide through erosion. This is a known phenomenon that can in principle be calculated and predicted based on a given sea-level rise, by means of the so-called Bruun effect.

However, things are a little more complicated when it comes to coastlines in the vicinity of inlets, such as river mouths, lagoons and estuaries. These places are affected by other factors, such as changes in rainfall due to climate change, and certain compensating effects (basin infilling).

Accurate model
 Until now, science has lacked a model that takes all these effects into account in the calculations of a coastline’s future development, even though a demand for this existed among engineers, coastal managers and planners.

The majority of coastline prognoses only took the Bruun effect into consideration. Scientist Rosh Ranasinghe, employed as associate professor at TU Delft and at UNESCO-IHE, has now succeeded in developing a new model that is able to produce much more accurate prognoses.

He did so together with researchers of the faculty of Civil Engineering and Geosciences at TU Delft, UNESCO-IHE and knowledge institution Deltares. With the model, it is possible to make accurate predictions quickly – within a few minutes – of how the coastline will develop in the vicinity of inlets as a result of rising sea-levels.

Underestimated
 The new model was in turn applied to four different and representative coastal areas (in Vietnam and Australia). The research showed that only 25 to 50 per cent of anticipated coastline change in these areas can be predicted using the Bruun effect.

The other processes that occur in the vicinity of inlets are of at least equal importance and coastline change in these areas as a result of rising sea levels has until now been strongly underestimated.

This new model makes it possible to make significantly improved prognoses of coastline erosion due to a rise in sea-levels. Coastal management projects that are being launched shortly will be able to benefit from this model, which means it can make a valuable contribution to coastal management and planning in practice.

The research is being partly supported by the Deltares Coastal Maintenance Research Programme.

‘Climate-change impact assessment for inlet-interrupted coastlines’ Roshanka Ranasinghe(1,2,3*), Trang Minh Duong (1,3), Stefan Uhlenbrook (1,2), Dano Roelvink (1,2) and Marcel Stive (2); 1 UNESCO-IHE, Department of Water Engineering; 2 TU Delft, faculteit Civiele Techniek en Geowetenschappen; 3 Deltares, Harbour, Coastal and Offshore Engineering DOI: 10.1038/nclimate1664

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More than 2.5 million acres of pinyon pine and juniper trees in the American Southwest during the past 15 years, killed by drought and mountain pine beetles

Filed under: Climate Change, Environmental, Wildlife — Leave a comment
July 7, 2012

Dying trees in Southwest set stage for erosion, water loss in Colorado River

by Staff Writers
Corvallis OR (SPX)


Pinyon pine forests near Los Alamos, N.M., had already begun to turn brown from drought stress in the image at left, in 2002, and another photo taken in 2004 from the same vantage point, at right, show them largely grey and dead. (Photo by Craig Allen, U.S. Geological Survey).

New research concludes that a one-two punch of drought and mountain pine beetle attacks are the primary forces that have killed more than 2.5 million acres of pinyon pine and juniper trees in the American Southwest during the past 15 years, setting the stage for further ecological disruption. The widespread dieback of these tree species is a special concern, scientists say, because they are some of the last trees that can hold together a fragile ecosystem, nourish other plant and animal species, and prevent serious soil erosion.

The major form of soil erosion in this region is wind erosion. Dust blowing from eroded hills can cover snowpacks, cause them to absorb heat from the sun and melt more quickly, and further reduce critically-short water supplies in the Colorado River basin.

The findings were published in the journal Ecohydrology by scientists from the College of Forestry at Oregon State University and the Conservation Biology Institute in Oregon. NASA supported the work.

“Pinyon pine and juniper are naturally drought-resistant, so when these tree species die from lack of water, it means something pretty serious is happening,” said Wendy Peterman, an OSU doctoral student and soil scientist with the Conservation Biology Institute. “They are the last bastion, the last trees standing and in some cases the only thing still holding soils in place.”

“These areas could ultimately turn from forests to grasslands, and in the meantime people are getting pretty desperate about these soil erosion issues,” she said. “And anything that further reduces flows in the Colorado River is also a significant concern.”

It’s not certain whether or not the recent tree die-offs are related to global warming, Peterman said. However, the 2007 report of the Intergovernmental Panel on Climate Change projected that while most of the United States was getting warmer and wetter, the Southwest will get warmer and drier.

Major droughts have in fact occurred there, and the loss of pinyon pine and juniper trees would be consistent with the climate change projections, Peterman said.

Pinyon pine and juniper are the dominant trees species in much of the Southwest, routinely able to withstand a year or two of drought, and able to grow in many mountainous areas at moderate elevation. The trees are common in Utah, Colorado, New Mexico and Arizona, and may have expanded their range in the past century during conditions that were somewhat wetter than normal.

In some places up to 90 percent of these trees have now died, many of them during a major drought in 2003 and 2004. The new research concluded that most of the mortality occurred in shallow soils having less than four inches of available water in about the top five feet of the soil column.

Most of the tree mortality, the scientists said, was caused by trees being sufficiently weakened by drought that opportunistic bark beetle epidemics were able to kill the pinyon pine, and the vascular system of the juniper ceased to function.

Traditionally, pinyon pine and juniper were not considered trees of significant value. They were occasionally used for firewood, but otherwise small and not particularly impressive.

They perform key ecosystem functions, however, not the least of which is stabilizing soils and preventing erosion. They also provide some food in the form of pine nuts and juniper berries, and store carbon in their biomass, and in the soils beneath their canopies.

 

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