Protect the world's deltas, experts urge

The Atchafalaya River delta meets the Gulf of Mexico. The view is upriver to the northwest. Credit: Photo courtesy A. Belala/U.S. Army Corps of Engineers

Extensive areas of the world's deltas -- which accommodate major cities such as Shanghai, Dhaka and Bangkok -- will be drowned in the next century by rising sea levels, according to a Comment piece in this week's Nature. In the article, Dr. Liviu Giosan, a geologist with the Woods Hole Oceanographic Institution (WHOI), and colleagues call for maintenance efforts to be started now to avert the loss of vast expanses of coastline, and the consequent losses of ecological services, economic and social crises, and large-scale migrations.

The authors state the problems start upstream: deltas are built from sediments deposited at the mouths of rivers, but dams and river engineering have lowered rates of sediment flow. The Nile and the Indus, for example, carry 98 percent and 94 percent less mud respectively than they did 100 years ago. At the coast, rising seas resulting from warmer global temperatures are eroding delta plains, increasing the chance of flooding. Coastal lands lower than a meter in elevation will be inundated within a century.

Lack of quantitative knowledge of basic delta processes is hindering efforts to develop maintenance strategies for deltas, the authors say. At the same time, the role of healthy marshes in coastal processes needs to be more fully understood. Giosan and colleagues call for river sediment flows to be restored, and natural land-building methods to be exploited in delta plains under worldwide monitoring programs coordinated and guided by United Nations committee of experts.

Source: Woods Hole Oceanographic Institution

Recreational activity a major pollutant on Canadian coast of Pacific Ocean

This is University of Calgary associate professor in geography Stefania Bertazzon.
Credit: Robert Walker

From recreational boats and fishing vessels to commercial cruise ships and private marinas, a newly published study shows that oil discharges related to human maritime activity on the Canadian coast is posing a major threat to marine ecosystems in the Pacific Ocean.

The study -- published in the August edition of the journal Applied Geography, with University of Calgary associate professor in geography Stefania Bertazzon as lead author -- provides a geospatial analysis of oil discharges in the Canadian Pacific Ocean.

The findings show that a large portion of oil discharge within these waters stems from recreational activities, passenger traffic and fisheries. According to this scientific analysis -- conducted on oil spills observed by the National Aerial Surveillance Program with the use of remote sensing devices -- these sources are polluting the ocean along the British Columbia coast more than oil tankers and commercial cargo ships.

"Cargo ships and oil tankers are much more regulated with portside inspections and they have to meet certain standards," explains Bertazzon. "They're very aware of this surveillance and this is probably why our analysis suggests that they are responsible for a smaller portion of detected oil discharges. They have to be more careful."

Bertazzon adds: "We're not saying that cargo ships and oil tankers are not polluting. What we are saying is that they are not the only source of pollution in the Canadian Pacific Ocean."
Bertazzon and her co-authors explain that fuel docks for recreational and fishing vessels can be problematic. "We know that there's a lot of oil discharge in these fuel docks, which is largely uncontrolled," she says.

"One thing that happens in these marinas is there's a lot of old boats which have been sitting there for years slowly leaking into the ocean. These are not huge spills. It's a relatively small discharge. But there's a lot of these derelict vessels and together they make for a large source of pollution."

While there's no denying the impact of large-scale oil industry disasters such as the Gulf of Mexico spill in 2010, Bertazzon argues that the oil discharges related to maritime activities are even more devastating to marine ecosystems in the long run.
"There is scientific evidence to show that these day to day activities have a larger impact on the wild life and the marine ecosystem than those accidents that are huge, but limited in space and time," says Bertazzon. "What we're talking about happens every day, all along the coast. The impact is longer term and over a larger spatial extent."

Source:  University of Calgary

'Tipping points' for sea level rise related flooding determined

Annapolis, Maryland, pictured here in 2012, is one of three major East Coast urban areas already being faced with nuisance flooding in excess of 30 days per year. Credit: With permission from Amy McGovern

By 2050, a majority of U.S. coastal areas are likely to be threatened by 30 or more days of flooding each year due to dramatically accelerating impacts from sea level rise, according to a new NOAA study, published today in the American Geophysical Union's online peer-reviewed journal Earth's Future.

The findings appear in the paper "From the Extreme to the Mean: Acceleration and Tipping Points for Coastal Inundation due to Sea Level Rise," and follows the earlier study, Sea Level Rise and Nuisance Flood Frequency Changes around the United States, by the report's co-author, William Sweet, Ph.D., oceanographer at NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). The new analysis was presented at a news conference today at the annual AGU fall meeting in San Francisco.

NOAA scientists Sweet and Joseph Park established a frequency-based benchmark for what they call "tipping points," when so-called nuisance flooding, defined by NOAA's National Weather Service as between one to two feet above local high tide, occurs more than 30 or more times a year.

Based on that standard, the NOAA team found that these tipping points will be met or exceeded by 2050 at most of the U.S. coastal areas studied, regardless of sea level rise likely to occur this century. In their study, Sweet and Park used a 1½ to 4 foot set of recent projections for global sea level rise by year 2100 similar to the rise projections of the Intergovernmental Panel for Climate Change, but also accounting for local factors such as the settlement of land, known as subsidence.

These regional tipping points will be surpassed in the coming decades in areas with more frequent storms, the report said. These tipping points will be also be exceeded in areas where local sea levels rise more than the global projection of one and half to four feet. This also includes coastal areas like Louisiana where subsidence, which is not a result of by climate change, is causing land to sink below sea level.

NOAA tide gauges show the annual rate of daily floods reaching these levels has drastically increased -- often accelerating -- and are now five to ten times more likely today than they were 50 years ago.

"Coastal communities are beginning to experience sunny-day nuisance or urban flooding, much more so than in decades past," said Sweet. "This is due to sea level rise. Unfortunately, once impacts are noticed, they will become commonplace rather quickly. We find that in 30 to 40 years, even modest projections of global sea level rise -- 1½ feet by the year 2100 -- will increase instances of daily high tide flooding to a point requiring an active, and potentially costly response, and by the end of this century, our projections show that there will be near-daily nuisance flooding in most of the locations that we reviewed."

"Communities across the country become increasingly vulnerable to water inundation and flooding, effective risk management is going to become more heavily reliant on environmental data and analysis," said Holly Bamford, Ph.D., NOAA acting assistant secretary for conservation and management. "Businesses, coastal managers, federal, state, and local governments, and non-governmental organizations can use research such as this as another tool as they develop plans to reduce vulnerabilities, adapt to change, and ensure they're resilient against future events."

"The importance of this research is that it draws attention to the largely neglected part of the frequency of these events. This frequency distribution includes a hazard level referred to as 'nuisance': occasionally costly to clean up, but never catastrophic or perhaps newsworthy," said Earth's Future editor Michael Ellis in accepting the paper for the online journal.

Ellis also observed that "the authors use observational data to drive home the important point that nuisance floods (from inundating seas) will cross a tipping point over the next several decades and significantly earlier than the 2100 date that is generally regarded as a target date for damaging levels of sea-level. The paper also raises the interesting question of what frequency of 'nuisance' corresponds to a perception of 'this is no longer a nuisance but a serious hazard due to its rapidly growing and cumulative impacts'."

The scientists base the projections on NOAA tidal stations where there is a 50-year or greater continuous record. The study does not include the Miami area, as the NOAA tide stations in the area were destroyed by Hurricane Andrew in 1992 and a continuous 50-year data set for the area does not exist.

Based on that criteria, the NOAA team is projecting that Boston; New York City; Philadelphia; Baltimore; Washington, D.C.; Norfolk, Virginia; and Wilmington, North Carolina; all along the Mid-Atlantic coast, will soon make, or are already being forced to make, decisions on how to mitigate these nuisance floods earlier than planned. In the Gulf, NOAA forecasts earlier than anticipated floods for Galveston Bay and Port Isabel, Texas. Along the Pacific coast the earlier impacts will be most visible in the San Diego/La Jolla and San Francisco Bay areas.

Mitigation decisions could range from retreating further inland to coastal fortification or to a combination of "green" infrastructure using both natural resources such as dunes and wetland, along with "gray" human-made infrastructure such as sea walls and redesigned storm water systems.

Source: National Oceanic and Atmospheric Administration

Colorado River Delta greener after engineered pulse of water

Water being released from Morelos Dam in the first environmental release of water to the Colorado River Delta. The Minute 319 pulse flow of water started March 23, 2014 and ended May 18, 2014. Credit: Rebecca Lester, Deakin University, Australia

The engineered spring flood that brought water to previously dry reaches of the lower Colorado River and its delta resulted in greener vegetation, the germination of new vegetation along the river and a temporary rise in the water table, according to new results from the binational team of scientists studying the water's effects.

The experimental pulse flow of water was the result of a U.S.-Mexico agreement called Minute 319.

"The pulse flow worked," said Karl W. Flessa, co-chief scientist for the Minute 319 Science Team. "A small amount of water can have a big effect on the delta's ecosystem."Starting March 23, 2014, and ending May 18, approximately 105,392 acre-feet (130 million cubic meters) of water was released into the dry river bed below Morelos Dam, which straddles the U.S.-Mexico border just west of Yuma.

"The groundwater was recharged, vegetation got greener than previous years and the water helped germinate new native vegetation," said Flessa, a University of Arizona professor of geosciences. "As a bonus, the river reached the sea."

In addition, people living along the river benefited, he said.

"People in the communities along the river were just overjoyed to see their river again," he said. "When the surface water was there, people celebrated. Kids who'd never seen water in the river before got to splash in it."

The science team includes more than 21 scientists from universities, government agencies and nongovernmental organizations from both Mexico and the U.S, including the UA, the Universidad Autónoma de Baja California, the U.S. Geological Survey, the U.S. Bureau of Reclamation, The Nature Conservancy, the Tucson-based Sonoran Institute and the Ensenada-based Pronatura Noroeste.

Flessa will present the team's findings at his talk, "The Science and Policy of the First Environmental Flows to the Colorado River Delta," on Dec. 18 as part of the American Geophysical Union's annual meeting in San Francisco.

Although most of the water soaked into the ground in the 37 miles (60 km) below the dam, the river's surface flow reached areas farther downstream that had been targeted for restoration. The increase in groundwater revived vegetation along the entire 83-mile (134 km) route to the sea.

By comparing Landsat 8 satellite images from August 2013 with those from August 2014, team members calculated a 23 percent increase in the greenness of riparian zone vegetation.
Although the groundwater did eventually recede, the surface water caused the germination of new willows and cottonwoods. Those plants germinate after natural spring floods, and their roots can grow fast enough to keep up with the receding water table.

The surface water reached the restoration sites prepared by the Sonoran Institute and Pronatura Noroeste and helped establish native vegetation.

"So long as the roots get down into the permanent water table, then you have established a new bunch of trees that will then live for 20, 30, 40 years," Flessa said. "Those trees will attract birds."

The scientists already observed an increase in the numbers of birds, he said.
Learning where the newly germinated plants survived past the first summer will help the researchers figure out where ecosystem restoration will do the most good using the least amount of water, he said.

"The water that soaked into the ground is also good for the farmers," Flessa said. "It raises the water table and they pump that water -- so this isn't just about trees and birds."
The team will continue to monitor the lower Colorado River Delta's vegetation and hydrological response to the pulse flow, including the long-term effect on groundwater. They will also study how the new vegetation affects both resident birds and those migrating along the Pacific Flyway.

The five-year program to monitor the environmental results of the pulse flow is being supported by government agencies and environmental groups in both countries, under the auspices of the International Boundary and Water Commission.

The Minute 319 pulse flow is part of a five-year agreement (2012-17) adopted by the International Boundary and Water Commission, under the framework of a 1944 U.S. -- Mexico treaty that governs water allocations on the Colorado River between the two countries.

The agreement provides multiple benefits for Colorado River water users in both countries, including environmental flows to the delta. Minute 319 identifies criteria for sharing of future water shortages and surpluses between the two countries, allows storage of Mexican water in Lake Mead and supports improvements to Mexican irrigation infrastructure.
"Another pulse flow would require a new agreement, because Minute 319 calls for only one pulse flow within the five-year term of the minute," Flessa said. "We hope the results of this pulse flow encourage the negotiators to make this happen again."

Source: University of Arizona