Category Archives: Erosion

Small Dams On Chinese River Harm Environment More Than Expected, study finds

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Jinanqiao Dam on the Jinsha River (Upper Yantze), built in high seismic activity, yet approved in 2012. Dammed, diverted and polluted, China’s rivers are reaching an ecological tipping point. Captions and Photo source: ©© International Rivers

By NSF

A fresh look at the environmental impacts of dams on an ecologically diverse and partially protected river in China found that small dams can pose a greater threat to ecosystems and natural landscapes than large dams.

Large dams have been considered more harmful than their smaller counterparts.

But researchers’ surveys of habitat loss and damage at several dam sites on the Nu River and its tributaries in Yunnan Province revealed that the environmental effects of small dams are often greater–sometimes by several orders of magnitude–than of large dams.

“Small dams have hidden detrimental effects, particularly when effects accumulate” through multiple dam sites, said Kelly Kibler, a water resources engineer who led the study while at Oregon State University.

“That’s one of the main outcomes, to demonstrate that the perceived absence of negative effects from small hydropower is not always correct.”

She and Desiree Tullos, also a water resources engineer at Oregon State, report their findings in a paper accepted for publication in Water Resources Research, a journal of the American Geophysical Union (AGU).

“These researchers have taken advantage of what is essentially a natural experiment that allowed them to compare the effects of hydroelectric dams of different sizes,” said Tom Baerwald of the National Science Foundation’s (NSF) Directorate for Social, Behavioral & Economic Sciences, which co-funded the research with other NSF directorates. “The results are applicable beyond this region.”

To compare the effects of small and large dams, Kibler investigated 31 small dams built on tributaries to China’s Nu River and four large dams proposed for the main stem of the Nu River.

She assessed the environmental effects of these dams in 14 categories–including the area and quality of habitat lost, the length of river channel affected, the amount of conservation land affected, and the landslide risk.

Because information regarding large dams is restricted under the Chinese State Secrets Act, Kibler modeled the potential effects of the four large dams using publicly-available information from hydropower companies, development agencies, and academic literature.

After evaluating data from the field, hydrologic models, and Environmental Impact Assessment reports on the small dams, Kibler and Tullos concluded that effects of the small dams exceeded those of large dams on nine out of the 14 characteristics they studied.

One particularly detrimental effect of the small dams is that they often divert the flow of the river to hydropower stations, leaving several kilometers of river bed dewatered, Kibler said.

From its headwaters in the Tibetan Plateau, the Nu River flows through China, Myanmar (Burma) and Thailand.

“While the number of small hydropower dams in operation or planned for tributaries to the Nu River is unreported,” the authors state in their paper, “our field surveys indicate that nearly one hundred small dams currently exist within Nujiang Prefecture alone.”

Thirteen large hydropower dams are proposed for the mainstem of the Nu River in Tibet and Yunnan Province in China.

Environmental, social, and economic factors make the Nu River basin extremely sensitive to hydropower installations.

In addition to supporting several protected species, the region is home to a large proportion of ethnic minorities and valuable natural resources, the authors report.

While large hydropower projects are managed by the central government, and both large and small hydropower projects undergo environmental impact assessments, decisions about small hydropower projects are made at a provincial or other regional level and often receive less oversight, Kibler and Tullos state.

The lack of regulation paired with a dearth of communication between small dam projects in China allows for the effects to multiply and accumulate through several dam sites, the authors write.

To mitigate the detrimental effects of small dams, there’s a need for comprehensive planning for low-impact energy development, said Kibler and Tullos.

“The lack of analyses of the cumulative effects of small hydropower,” Kibler said, “is a significant research gap with important policy implications.”

Original Article, NSF

Dams In China, by International Rivers
Dammed, diverted and polluted, China’s rivers are reaching an ecological tipping point. China has more large dams than any other country in the world, including the world’s largest – the Three Gorges Dam. Chinese companies are rapidly exporting their large dam-building model overseas. Chinese banks and companies are involved in constructing some 300 dams in 66 different countries, particularly in Africa and Southeast Asia.

Largest Dam in State History Torn Down, California

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San Clemente Dam on California’s Carmel River after rainfall. Captions and Photo source: NOAA

Excerpts;

Monterey County supervisors gave their OK for the largest dam removal project in state history. The San Clemente Dam is eighteen miles from the coast in the Carmel Valley…

Read Full Article, ABC News

San Clemente Dam removal project to start by August, Monterey Herald
The long-awaited San Clemente Dam removal project is scheduled to begin this summer after California American Water earned the final go-ahead…

NOAA and California Officials Agree to Remove Large Concrete Dam to Eliminate Safety Hazard and Restore Steelhead Habitat, NOAA
NOAA joined state and local officials in a pledge to remove the San Clemente Dam to eliminate a threat to the lives and property of those along California’s lower Carmel River, and help restore the watershed for federally protected steelhead trout.
The 89-year old, 106-foot high dam, which once helped bring water to residents of Monterey County, is at risk of failing during a significant earthquake or flood. Sediment has been building up behind the dam for years, making it a hazard for those living below it and almost useless as a water storage reservoir. If the dam were to fail, an estimated 2½ million cubic yards of sediment and more than 40 million gallons of water could rush downstream with potentially disastrous consequences. The dam removal will also aid in the recovery of steelhead trout by opening up access to more than 25 square miles of spawning and rearing habitat. Steelhead in Carmel River were listed as threatened under the Endangered Species Act in 1997…

San Clemente Dam Removal & Carmel River Reroute Project

On The Elwha, A New Life When The Dam Breaks, Washington State (Uploaded 09-18-2011)
Nobody figured the largest dam removal project ever attempted in the U.S. was going to be easy, or fast. The nation’s largest and most ambitious dam removal will begin this month, when workers start demolishing two antique dams on Washington state’s Elwha River…

Tracking Sediments’ Fate In Largest-Ever Dam Removal (Uploaded 03-08-2013)
Scientists tracking the aftermath of the largest dam removal in U.S. history say the dismantling of a dam in northwestern Washington state has unleashed about 34 million cubic yards of sediment and debris that built up for more than a century…

World’s Tallest Dam Approved by Chinese Environmental Officials

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Chinese companies and Chinese banks are now the biggest builders and financiers of global dam building. Chinese banks and companies are involved in some 307 dams in 74 different countries, particularly in Africa and Southeast Asia, including Kamchay Dam (Cambodia), Bakun Dam (Sarawak, Malaysia), Myitsone Dam (Burma) and Merowe Dam (Sudan). Captions and Photo source: ©© International Rivers

Excerpts;

Chinese environmental authorities have approved construction plans for what could become the world’s tallest dam, while acknowledging that the project would affect endangered plants and rare fish species…

Read Full Article, Guardian UK

China’s Global Role in Dam Building, International Rivers

The Problems With Dams

Controversial dam projects – in pictures, The Guardian UK
A look is taken at some of the world’s most contentious dam projects, from the Three Gorges in China to Brazil’s Belo Monte dam.

Elwha Dam Removal: A New Life When The Dam Breaks

“It’s happening now, The village is sinking”

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Alaska, Houses collapsing due to coastal erosion.
Villages and homes are being destroyed by a rising tide, to the point where homes are being abandoned as they literally fall into the ocean. Residents can do nothing to stop the water as it approaches their homes. Captions and Photo source: ©© Laurence Hislop / UNEP
On the same coast than Kivalina, the village of Shishmaref in North Western Alaska, inhabited for 400 years, is currently facing evacuation due to rising temperatures, which are causing a reduction in sea ice, thawing of permafrost along the coast. The reduced sea ice allows higher storm surges to reach shore and thawing permafrost makes the shoreline more vulnerable to erosion. The town’s homes, water system and infrastructure are being undermined. Captions: NOAA

Excerpts;

Residents of Newtok, on the shores of the Bering Sea, Alaska, know they must evacuate as the village is rapidly losing ground to erosion, but who will pay the $130m cost of moving them?

Read Full Article, Guardian UK

Court Rules Against Village In Global Warming Case
A federal appeals court has ruled against the northwest Alaska village of Kivalina, which sued energy companies over claims that greenhouse emissions contributed to global warming that is threatening the community’s existence. (Uploaded 09-11-2012)

Erosion doubles along Alaska’s Arctic coast
Coastal erosion has more than doubled in Alaska, up to 45 feet per year, in a 5-year period between 2002 and 2007 along a 40-mile stretch of the Beaufort Sea. A U.S. Geological Survey-led study reveals that average annual erosion rates along this part of the Beaufort Sea climbed from historical levels of about 20 feet per year between the mid-1950s and late-1970s, to 28 feet per year between the late-1970s and early 2000s, to a rate of 45 feet per year between 2002 and 2007. The authors proposed that these recent shifts in the rate and pattern of land loss along this coastline segment are potentially a result of changing arctic conditions, including declining sea ice extent, increasing summertime sea-surface temperature, rising sea level, and increases in storm power and corresponding wave action.
Around the world, as many as 150 million people may become “climate refugees” because of global warming, according to an Environmental Justice Foundation report, which attributes some of the moves to rising sea levels…

Human and Economic Indicators, Shishmaref, NOAA
The village of Shishmaref in N. Alaska, inhabited for 400 years, is facing evacuation due to rising temperatures, which are causing a reduction in sea ice, thawing of permafrost along the coast. The reduced sea ice allows higher storm surges to reach shore and thawing permafrost makes the shoreline more vulnerable to erosion. The town’s homes, water system and infrastructure are being undermined.

“I went to school on the mainland, and when I came back, my house was gone. They moved it to the other side of the village, or it would’ve fallen in.” Leona Goodhope, Shishmaref, Alaska (from ACIA)….

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Shishmaref, Alaska. Photo source: ©© Alaska teacher

Scripps Oceanographers Study Coastal Erosion, UC San Diego

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Beach erosion after a Pacific storm, Torrey Pines Beach, San Diego, CA. Captions and Photo source: ©© Abraxas3d

Excerpts;

San Diego’s coast is a precious resource for beachgoers, marine life and our county’s economic well-being. It’s also an ever-changing ecosystem threatened by erosion. With 70-plus miles of pristine beauty, the US’s western coastline is constantly shifting…

Read Full Article, CBS

San Diego’s Eroding Coastline, Video

Scripps Institution

Relief for a Parched Delta

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Colorado River into the Gulf of California, Sea of Cortez.
These two pictures illustrate the extremes of water flow in the Colorado River since measurements began in the late 1800s. The 1985 image (Left) was taken in the midst of record high flow, while the 2007 image (Right) shows the driest period. Excessive rains or severe droughts directly change the amount of water available in the Colorado River Basin, and so does the increasing pressure of human needs throughout the western states. The river, which has its headwaters in the snowmelt of the Rocky Mountains, is 1,400 miles (2,253 kilometers) long and empties into the Gulf of California, also known as the Sea of Cortez. Captions and Images source: U.S. Department of the Interior / USGS and NASA.

Excerpts;

Germán Muñoz looked out at the river before him and talked about the days when dolphins swam here, 60 miles from the sea…

Thanks to dams that throttled the Colorado and diverted its water to fuel the rise of the American West, the river has effectively ended at the Mexican border. The Colorado delta, once a lush network of freshwater and marine wetlands and meandering river channels and a haven for fish, migrating birds and other wildlife, is largely a parched wasteland…

Read Full Article, The New York Times


Colorado River Delta, Baja California: Earth Observatory / NASA

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By NASA,

The Colorado River is the largest watershed in the southwestern US, emptying into the Salton Trough before reaching the Sea of Cortez. Over the past 2-3 million years, river sediments built a delta that extends from the US-Mexico border for a distance of 87 miles (140 km). However, today the Colorado River delta is undergoing significant erosion and diminishing in size due to the lack of sediment replenishment from upstream sources.

This image highlights the generally arid setting of the Colorada River delta estuary at its terminus and at low tide.

The Desierto de Altar occupies the right portion of the image. The extensive white salt flats to the southeast of the Cienega (wetland) de Santa Clara are clearly visible. This brackish wetland is a major stopover point for Pacific shore bird migrations and is maintained by groundwater pumped from the southwestern USA.The channel extending from the large island in the center of the image (Isla Montague) to the northwest is an inlet from the Gulf of California which formed after the Colorado River receded due to impoundment of water by Hoover (1935) and Glen Canyon (1964) dams.

It crosses floodplain sediments (gray to dark brown) left by the original river. Gray-brown linear streaks extending southeast from Isla Montague into the Gulf are floodplain sediments mobilized by tidal surges and wave action rather than fluvial processes. Dark green areas bordering the channel, shoreline, and Isla Montague are riparian and estuarine vegetation.

Prior to impoundment of water from upstream dams the delta provided habitat for a wide variety of species including shrimp, corvina fish, and vaquita porpoise. Replacement of water into the delta from groundwater and upstream releases have helped to revive some of the preexisting habitat. This reinvigorated habitat also supports a local ecotourism industry within the delta region. Continuing drought conditions affecting the southwestern USA may decrease water delivery to the delta with significant impacts on both the ecologic and economic health of the region.