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Towering Hills for Beauty and Strength

Governors Island

Photo: Timothy Schenk

A dozen years ago an American port representative was asked how his port was preparing for rising sea levels. “Well…we aren’t,” he answered, somewhat sheepishly, because he knew they should be. Back then, the public was skeptical of the controversial topic, and frankly many ports had too many other priorities. But now public officials see the situation in a new light. They are taking advantage of waterfront development projects to make property not only more resilient to climate change, but also more beautiful and beneficial to the public.

A perfect example is the 40-acre Governors Island Park and Public Space in New York. West 8, an urban design and landscape architecture firm, transformed the abandoned former military island into a green oasis with an extraordinary 360-degree experience of water and sky that has won numerous awards. Part of the makeover involved creating four tall, dramatic hills from twenty-five to seventy feet high. This meant overcoming a major challenge involving Governors Island history.

Governors Island Park and Public Space

Pumice, or lightweight fill (the light colored material) is placed on the water side of the tallest hill. Image courtesy of West 8

From Subway Dirt to Island

Back in 1637, when a Dutch man bought Governors Island for two ax heads, a string of beads, and some nails, the island was only about 72 acres. In 1901, somebody needed a place to discard the dirt from the excavation of New York’s Lexington Avenue subway line. What better place to put it than Governors Island? The dirt widened the island by 100 acres.

Fast forward to the twenty-first century. Now that the island had been sold back to the people of New York for one dollar, it was possible to take advantage of the island’s potential views, which meant building upwards. To create the new hills, West 8 needed to add 300,000 cubic yards of new fill—enough to fill 40 Goodyear blimps. The challenge was to keep that massive amount of dirt from pushing the island built on subway fill out into the harbor.

Hart Crowser worked with the lead civil engineer to make the hills strong yet light. Twenty-five percent of the new fill is from the demolition of structures and parking lots. This made it sustainable and strong. Pumice lightened the load. Some of the fill was wrapped in geotechnical matting, and the steepest slopes used wire baskets. This allowed hills as high as seventy to be built within twenty feet of the shoreline, and allowed for varying slopes and walkways, where the public can safety enjoy the park.

Governors Island reopened to the public on May 28.

First Tsunami Safe Haven Building in the United States

Ocosta School Construction

The City of Westport stands sentry at the tip of a narrow peninsula between the expanse of the Pacific Ocean and the protection of Grays Harbor. The Cascadia Subduction Zone, a 700-mile-long earthquake fault zone, lurks approximately 90 miles off the shore. Experts predict this submerged fault zone will release a magnitude-9.0 earthquake and unleash a tsunami that will hit the coasts of British Columbia, Washington, Oregon, and California. The last such “megaquake” struck just over 300 years ago.

As was recently seen in Chile, Indonesia, and Japan, tsunamis ravage low-lying areas such as Westport. There, it is expected that a tsunami from a Cascadia Subduction Zone megaquake could reach the coast in as little as 20 minutes. However, evacuation of Westport and neighboring Ocosta Elementary, Junior and Senior High Schools could take nearly double that time. Therefore, in 2013 residents of the Ocosta School District approved re-construction of an aging elementary school that will include the nation’s first tsunami “refuge” structure.

Construction of the school started in November 2014. The school’s gym has been designed to withstand the impact of a tsunami and the debris it carries, while sheltering nearly 1,000 people on its roof. The roof is 30 feet above the ground (nearly 55 feet above sea level) to keep people dry and safe. The gym’s roof is supported by heavily reinforced concrete towers in each corner that are designed to remain intact during shaking from the initial megaquake, associated aftershocks, and the resulting tsunami surges.

Because of the potential for over 10 feet of scour (soil erosion adjacent to the building) caused by tsunami surges and liquefaction of the native sandy soils, the gymnasium is supported on nearly 50-foot deep piles. The remainder of the school is supported on shorter piles designed to withstand earthquake shaking and liquefaction, but not necessarily tsunami surge forces.

Links below lead to more information on the Ocosta building and general tsunami research. Note that the maps on the last link (Project Safe Haven) illustrate how impossible it would be to escape a tsunami in the Ocosta area.

Rooftop Refuge Washington Disaster News, Washington Military Department Emergency Management Division
Grays Harbor County school to build first U.S. vertical-tsunami refuge Seattle Times
First tsunami-proof building to be built in Westport Komo News
Rising above the risk: America’s first tsunami refuge the Geological Society of America
Project Safe Haven: Tsunami Vertical Evacuation in Washington State

Three Reasons Eelgrass is Declining—What’s Being Done?

Dredging

In an earlier post we showed how important eelgrass is to fish, and noted that eelgrass is declining worldwide. West coast eelgrass is affected by a combination of coastal development and nutrient pollution, direct displacement (such as dredging activities), and climate change.

Here’s why:

Eelgrass needs light. Urbanization and construction activities in coastal areas remove vegetated buffers, allowing more runoff into the water. Runoff carries sediment, which reduces water clarity. Also, nutrients from wastewater, stormwater, and other human activities can promote algae blooms, which also block light.

Dredging uproots eelgrass; filling buries it. These activities can completely decimate an eelgrass meadow even beyond the footprint of direct impact. It can take ten years or more for eelgrass to recover, if at all.

Climate change: as ocean temperatures rise, native plants feel the heat. Evidence shows that northern eelgrass populations will not adapt to warmer waters as easily as southern eelgrass populations might. Their photosynthetic engines just can’t keep cool enough. Also, as a consequence of climate change, sea level is rising, meaning eelgrass will have to move to keep the same relative depth. It can’t move far before a hardened structure such as bluff or even a seawall stops it.

The State of Washington is acting to restore eelgrass across Puget Sound. The Puget Sound Leadership Council established a target of expanding the total area of eelgrass beds by 20 percent by 2020. Major restoration efforts have already been undertaken, and more are underway. New plantings are proposed for the Nisqually, Skokomish and Elwha river deltas. In these places, restoration may have a better chance to succeed because of improved sandy substrate and restored water quality.

Section3B_Marine-Nearshore_AcresEelgrass

Acres of Eelgrass in Puget Sound

More information: shedding new light on eelgrass recovery and threats and human impacts on eelgrass.

Eelgrass—Nowhere to Hide

Bay Pipefish in Eelgrass

Bay Pipefish (Syngnathus leptorhynchus)–one of many species that depend on eelgrass habitat for survival.

A marine ecologist in Hart Crowser’s Anchorage, Alaska office, overheard a recent complaint, “When I go fishing I can’t stand all this ‘eelweed’ getting in my prop and fouling my lines.”

“Then why do you fish where there is eelgrass?” asked the marine ecologist.

“Because that is where fishing is best.”

That was the crucial connection. Eelgrass is essential fish habitat. Without it, even migratory fish (including our beloved salmon), don’t have a place to call home.

Eelgrass (Zostera marina) is native to shallow waters of most temperate oceans and seas, including Puget Sound, Oregon, northern California, British Columbia, and Alaska. It is not a seaweed like kelp, but a flowering plant that evolved from terrestrial flora (similar to what you might find in your front yard).

Eelgrass is important to many fish and invertebrates. Juvenile salmon, rockfish, and Dungeness crab find shelter in eelgrass meadows in early life. Herring, in particular, spawn on eelgrass, making it crucial to its survival. Many species (including commercially important ones) use it to live, eat, spawn, and hide from predators.

Eelgrass is also very good at converting carbon dioxide into tissue that may get buried, taking it out of the system (blue carbon). An acre of eelgrass can remove nearly 150 kg of carbon from the atmosphere every year, making it important to the issues of ocean acidification and global climate change.

Eelgrass is pretty hearty, dealing with coastal storms, being exposed at low tide, and spending part of each year under sea ice (in northern areas). Yet, as hearty and important as eelgrass is, it is on the decline, leaving fish and invertebrates that depend on it with nowhere to hide. Stay tuned for the reasons why, and what’s being done about it.