Resilience Concepts Behind Living Breakwaters

I was asked by an intern at City Atlas, Travis Gonzales, to answer his well-posed questions on our winning Rebuild By Design entry, Living Breakwaters, and here is that Q&A, which I think gets addresses some important aspects of the concept.

1. The proposal for Living Breakwaters states that the breakwater system developed to protect Staten Island’s coastline could be used in other vulnerable communities. Yet, the Island’s location at the mouth of the harbor makes for a special case of erosion. Do you think that a proposal like this, and Rebuild’s competition by extension, supports experimenting with coastal protection locally in a way that can be used throughout the coastal US?

Staten Island is a somewhat unusual semi-protected coastal location, where waves are typically small, but can be large during coastal storms.  However, the irregular US Northeast coast has many locations with similarities, such as beach areas near Boston, as well as all of coastal Masschusetts and New Hampshire.

A distinguishing feature of a coastal area like that of Staten Island is that waves are not a normal feature utilized for recreation, such as surfing.  So, it’s an ideal location where modification of the wave climate will not cause opposition of surfers and others who enjoy the waves.  However, the approach could also be used selectively at open coastal locations where there is surfing, as long as surfers are brought into the process of planning reefs that they might enjoy using for surfing.

2. Because the breakwaters aren’t a type of levee or berm but instead a buffer, how long do you think they will remain effective, given issues like continual sea level rise or the potential for stronger storms?

One of the main innovations with the breakwaters is that they are designed to GROW with sea level rise, as oyster beds can easily grow at a similar or faster rate.

In terms of extreme storms, which can happen today and aren’t only a thing of the future, the breakwaters gradually become less effective at reducing wave heights as a flood deepens above them.  But this is part of the plan; the purpose of our approach is actually to NOT have a flood elevation where the adaptation abruptly becomes useless (or worsens the dangers).

This is in contrast to levees, which always have a “design height” and this is typically the height of a 100-year storm, plus one or more extra feet allowing for sea level rise.  Once the flood goes above a levee design height you have abrupt rushing water filling in the “protected” area, which can make the hazard MORE deadly than a gradually rising water level.   In New Orleans, this occurred many times over and over through history, not just in 2006 (see this reference).  The paired problems of sea level rise and urban coastal flooding is a very complex and dynamic problem involving not just physical flooding, but also sociology, psychology (do I evacuate?), economics and politics.  Levees are a static solution to this very dynamic problem.

3. Staten Island coastal areas, while good for recreation, do not have the same vital infrastructure points as Lower Manhattan. Why is protecting Staten Island a concern for New York City?

Actually, the project isn’t really about “protecting” Staten Island.  It aims to improve the area’s resilience in a much broader way, including economics and coastal storms.  We do this by restoring Staten Island’s historical water culture, reducing flood and wave risks, reducing erosion, improving educational and recreational opportunities at the shore, and thus making the ocean tides and waves (and their risks) more visible and tangible.  It’s much broader.

New York City has a very large coastal population in flood zones, and they expect something to be done in response to Sandy, and the options often boil down to vertical protections (e.g. levees) and other options, and we feel we have created a very appealing alternative.  That being said, our living breakwaters are an offshore option, and communities can still work with the city and Corps of Engineers to build vertical protections such as dunes or levees.

4. If you have any other thoughts or insights on Rebuild by Design that you’d like to share, please do.

When there is a disaster, the political response by government is to try to help people and to stop the same disaster from happening again.  But when it comes to coastal flooding, it’s also important to have some sort of long-term thinking.  We know we have many feet of future sea level rise coming, possibly within just this century, and simply stopping today’s flooding problem isn’t necessarily the best solution.

This was the brilliant justification behind Rebuild By Design — bringing the world’s designers, scientists and engineers together to come up with new ideas for more forward-thinking solutions to the increasing problem of sea level rise and coastal flooding.

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Living Growing Breakwaters and Building Community Resilience

We had great news a few weeks ago — our team was selected as a winner of the HUD Rebuild By Design competition, and New York State is being awarded $60 million to build out our project — Living, Growing Breakwaters off Staten Island.

Kate Orff and her team at the SCAPE design firm built the team and led the effort, and it was an honor to get to be a part of it.  For the final review, teams were asked to make videos, and here is the one by our team – it keeps getting positive reviews, so is worth sharing far and wide.  In it, we explain many of the innovative aspects of our living growing breakwaters, as well as our approaches to stepping down risk instead of falsely hoping to eliminate it, making the hazard more visible and making urban coastal communities more resilient through education and interaction with the ocean.

I recommend watching the video, but in case you would like to read, the transcript of my statements on coastal flood adaptation and how we used ocean modeling to test our breakwaters follows.

The layering of coastal protections is important because sometimes one protection type such as a levee can fail or be over-topped.  It’s better to have multiple, layered protections and that can come in many forms.  Having an ecological approach, one case would be to have large expanses of oyster reefs or wetlands that can reduce the flooding before it reaches your seawall.

We were reminded by Sandy that this region, northern New Jersey and New York City, is susceptible to being hit by a hurricane, which hadn’t happened in over 100 years.  And so we were reminded that we have to deal with this issue sooner than we realized with sea level rise and natural storm surges that don’t even necessarily have to do with climate change.

In the case of the storm surge, Raritan Bay is in a bad location, and Staten Island is very vulnerable to storm surge because it is in more of a funnel shaped area where the storm surge comes in and it actually gets larger as it comes into the point of that funnel.

Peak water elevations during Hurricane Sandy in meters above mean sea level

Modeled peak water elevations during Hurricane Sandy in meters above mean sea level. With Sandy “captured” by the computer model, we can run experiments on the storm, testing how different adaptation strategies can impact flooding and waves.  

A benefit of computer models is that they synthesize all scientific understanding of coastal storm surge and waves and they give us an objective answer.  Many people have an opinion or even political viewpoints driving what they think we should do about coastal flooding and sea level rise, but the benefit of computer models is that they give us an objective answer based on the best available science.

In terms of risk reduction, the goal of the breakwaters is only to reduce wave impacts at the coast, not to stop storm surge, and it leaves the choice of what is done at the coast (e.g. dunes, raised berms) to the Corps and local communities.  The model results show an up to 4 foot reduction in wave height at Staten Island’s shore (during a Sandy-like storm), which could ultimately reduce erosion during winter storms, make the coastal areas safer during more extreme storms, and reduce the FEMA V-Zones and Coastal A-Zones.

Risk reduction doesn’t always have to come in the form of vertical walls.

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Increasing storm tides in New York Harbor, 1844–2013

We published a paper in the journal Geophysical Research Letters in May (paper, supporting information), and a very important yet simple result from the paper is that Stefan Talke (Portland State University) recovered historical sea level data from NY Harbor and created this great 1844-2013 dataset for annual maximum storm tide that is twice as long as datasets previously available.

Annual Maximum Storm Tide from gauges around the New York Harbor area.  The error bars denote the estimated precision, and the dashed horizontal line depicts the 1.75m AMST threshold (a nominal seawall height for Manhattan).

Annual Maximum Storm Tide (AMST) from sites around the New York Harbor area. The error bars denote the estimated precision, and the dashed horizontal line depicts the 1.75 m AMST threshold (a nominal seawall height for Manhattan).

This figure shows the annual maximum storm tides (AMST) in meters above mean sea level — water levels purely driven by storm winds, atmospheric pressure, and tides. Looking at these data one can clearly see that the storm tides have been increasing, and much of the paper is about quantifying this trend and also the variability. Each bar on the plot represents a year’s maximum flood height minus that year’s mean sea level, so sea level rise is not the reason you see increasing AMST.

A sound-byte in the media articles has been the part of the final sentence of the paper’s abstract, which reads “… the annual probability of overtopping the typical Manhattan seawall [has risen] from less than 1% to about 20-25%.”  This is unquestionably a powerful result!

This has led to headlines such as this one from Salon:

Manhattan’s surging flood risk: City could end up underwater every 1 in 4 years” – Salon.com (with a photograph of deep-water flooding in Manhattan during Sandy)

I want to make clear that just because a seawall is overtopped doesn’t mean the city is “underwater”.  There are many different flood height thresholds for flooding different neighborhoods, and the 1.75m threshold is just a nominal Manhattan seawall height (from Colle et al. 2008) and even those vary substantially in height.  The National Weather Service considers a 1.8m flood height to be the threshold for “moderate flooding” at NY Harbor.  But in most places, only a waterfront walkway or park floods with a 1.75m or 1.8m flood height, and neighborhoods are dry until the flood height reaches a higher elevation.

We are trying to work with NYC to quantify what neighborhoods flood at what flood heights, but we already know that at least a few neighborhoods of NYC are susceptible to flooding at low levels of ~2m (about a 10-year flood event).  On the other extreme, we also know that about 5% of the city population had floodwaters during Hurricane Sandy.

Stefan and I estimate Sandy to be a roughly 300-year return period flood event (unpublished work), so this is not something I personally expect to occur again frequently.  This estimate is based on historical data only, and if storms are changing, then it may underestimate the frequency of such floods.  There is some evidence for an increase in North Atlantic storms and their intensity (National Climate Assessment, 2013, Chapter 2), but scientists are still debating whether climate change is responsible and whether the trend will continue into the future.

A less frequent focal point of the media is the great story of discovery of the historical data, explained in this nice video:

The American Geophysical Union did a great job with the video, capturing the wonder and excitement of the data archaeology and research.

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Winter Coastal Storms – a Dangerous Mix of Hazards

The winter storm hitting us right now is a reminder of how coastal flooding and winter storms can mix and bring a dangerous combination of hazards.  While the winds in this storm are substantially weaker (good news) than the Blizzard of ’78, both storms hit during extreme spring tides. The 1978 storm was the worst flood event on record for places like Boston.

Winthrop Drive, in the Beachmont section of Revere, Mass., was flooded by waves and tidal surge during the Blizzard of '78 that overflowed the seawall (credit: The Boston Globe)

Winthrop Drive, in the Beachmont section of Revere, Mass., was flooded by waves
and tidal surge during the Blizzard of ’78 that overflowed the seawall and froze in the streets (credit: The Boston Globe)

The Blizzard of ’78 caused record flood levels and also multiple feet of snow.  Combined with freezing temperatures this led to a very dangerous disabling of coastal communities in the Gulf of Maine and Massachusetts Bay.

Rescue worker struggles to haul evacuation boat to the front door of this home in Revere, Mass (photograph by Paul Benoit, Boston Herald American).

Rescue worker struggles to haul evacuation boat to the front door of
this home in Revere, Mass (photograph by Paul Benoit, Boston Herald American).

The storm surge forecasts at New York City, Long Island Sound, and the New Jersey Shore for this evening’s storm are only calling for about 2 feet of storm surge, but it is coming on top of some of the year’s highest tides.  We do not provide forecasts for Boston, but our forecasts for The Battery and Kings Point, in the NYC region, suggest only a 1.5 foot and 2.0 foot surges, respectively.  NOAA’s two models predict a ~2.5 foot surge and ~3 foot surge at these same locations.

caption

Stevens NYHOPS Storm Surge Warning System forecast for water levels at Kings Point (magenta), relative to mean lower low water (MLLW – normal daily low tide). Predicted tides are also shown (blue), as well as observed water levels (red) and two NOAA ET-Surge forecasts for comparison (green).

Above is the figure showing the astronomical tides, as well as several forecasts for water level, suggesting that moderate flooding (barely over seawalls in a few places) may occur in Long Island Sound.  Flood levels in the direst forecasts at the moment are more than 6 feet lower than those seen during Sandy for The Battery and ~3 feet lower at Kings Point, Long Island Sound.  Check for yourself as the storm proceeds, using the Storm Surge Warning System.

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Air Quality Measurements on Your Own Window Sill

[This is a guest blog post from Talmor Meir, a PhD student at Stevens Institute in the Maritime Security Laboratory.]

egg1

Good news to NYC and it’s neighbors: According to The New York Times air across our city is the cleanest it has been in at least 50 years.  The conclusions were based on the NYC Air Quality Survey, where measurements are taken at 150 locations throughout NYC metropolitan on a seasonal basis and applied regionally.  While I am in support of any effort done to improve the air we breathe, I think we, the citizens of NYC, can do better.  We can increase air quality awareness by improving our measurement resolution.  Let’s talk about air quality on a finer scale, in our own neighborhoods, on our own street, right outside our windows!

Air Quality-EGG is a project aiming to give citizens a way to participate in the conversation about air quality in their immediate environment. The egg resembles an ostrich egg that sits outside your window or inside your home. It has four sensors built in – Temperature, Humidity, Carbon Monoxide, and Nitrogen Dioxide. The Egg receives information from the sensors every minute and uploads it to a network cloud making all data accessible to the public. The idea is that if we implement such technology into our homes, schools and office spaces, we, the citizens and workers of New York, together, will be able to map the evolution of daily air quality across different neighborhoods.

Our atmospheric science and air pollution research group (Pullen, Meir, Orton, Blumberg) is trying to help encourage more citizens to join in this effort, to strengthen and broaden the network.  You can help us gain higher resolution across the NYC by implementing your own egg at home or work.  Air Quality Eggs can be ordered from https://shop.wickeddevice.com for $185.  The setup is simple and I have found the support team for this project to be very responsive.  The egg is pre-assembled and you will be asked to create a profile for your egg, where you get to name it and include details such as location, what floor you live on, indoor/outdoor placement, etc.  Once you connect it to your internet router (just like you would any other computer in your home), it begins collecting data.  You can then see your specific egg and all other available active eggs across the world at: http://airqualityegg.com.

egg2

Whether you purchase the Air Quality Egg or not, you can become part of the conversation by spreading the word and become active in chat forums and other media.  Visit this blog again soon to see some analysis of my Egg’s data, located down on Wall St, NYC, or simply follow my Egg’s measurements on your own using the map on their website.

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HUD Rebuild By Design: Plans for the Future Coast

I am honored to be part of a well-constructed, diverse-minded team for the HUD (federal Housing and Urban Development) post-Sandy “Rebuild By Design” competition, one of 10 successful teams of about 150 that applied.  The team was built and is guided by SCAPE Studios and Kate Orff, and includes designers, coastal engineers, the creators of ECO-ncrete, oceanographers, maritime high school educators, and a well-known expert on coastal fisheries, among other areas of expertise.  It brought a very wise mix of expertise and ideas on both physical and social resilience to the table.

The results of the “phase 2″ set of coastal adaptation approaches are online, and four come from our team.  HUD-RBD organizers, including the Rockefeller Foundation, are seeking input on the entries, so please go and see what you think!

The entire page of entries, with a clickable map to locate one in your location, are linked here:  http://www.rebuildbydesign.org/design-opportunities/

The entries from our team are:

Gardening The Bay: Jamaica Bay, NYC, http://www.rebuildbydesign.org/project/gardening-the-bay-jamaica-bay-nyc/

Living, Growing Breakwaters: Staten Island and the Inner Harbor, http://www.rebuildbydesign.org/project/living-growing-breakwaters-staten-island-and-the-inner-harbor/

More Wet Meadow, Less Land: Hackensack River, NJ (The Meadowlands), http://www.rebuildbydesign.org/project/more-wet-meadow-less-lands-hackensack-river-nj/

Barnegat Bay Remade: Barnegat Bay, NJ, http://www.rebuildbydesign.org/project/barnegat-bay-remade-barnegat-bay-nj/

You can actually leave comments and questions on the RBD website, with each entry.

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Hurricane Sandy Storm Surge Map Animations

Hurricane Sandy was a wild beast, with a powerful high pressure system, a hurricane, a nor’easter and a high tide all meeting simultaneously to cause the highest flood in NYC history.  As a result the peak flood height was poorly forecast by federal and academic scientists.  One of our main pursuits at Stevens Institute’s Davidson Laboratory (aka Center for Maritime Systems) has thus been “capturing Sandy” — creating a reproduction that is as accurate as possible.

Click to see an animation of Hurricane Sandy modeled wind and pressure driven storm surge (color shading) from Hatteras to Nova Scotia. Arrows are wind velocity vectors (see the scale arrow for a 33 m/s or 74 mph hurricane strength wind), contours are isobars - lines of constant atmospheric pressure. An inset panel shows the four day time-history of modeled surge near NYC's shoreline at Sandy Hook.

Click to see an animation of Hurricane Sandy modeled wind and pressure driven storm surge (color shading) from Hatteras to Nova Scotia. Arrows are wind velocity vectors (see the scale arrow for a 33 m/s or 74 mph hurricane strength wind), contours are isobars – lines of constant atmospheric pressure. An inset panel shows the four day time-history of modeled surge near NYC’s shoreline at Sandy Hook.

In order to do this, we needed to find the best representation available of Sandy’s winds and pressure, and accurately simulate Sandy’s storm surge using our ocean model.   We also then needed to compare the resulting flood heights around the region to verify that they are accurate (they are, to an average across several tide gauge stations of 15 cm rms error for the animation above, 16 cm rms error for the animation below).  

Above is an animation of Sandy’s winds, barometric pressure, and storm surge, which is just the wind- and pressure-driven water elevation.  Credits for our ocean modeling also go out to my colleagues Alan Blumberg and Nickitas Georgas.  It is based on the Stevens Northwest Atlantic Predictions (SNAP) model grid that we built last fall, as forced by atmospheric model forecast data from the NOAA National Center for Environmental Prediction Global Forecast System (GFS).  I also have made a 3-minute version with voice-over descriptions of what is occurring.

Note how the winds blew from the northeast across the coastal Atlantic Ocean during the three days leading up to Sandy’s landfall, and this started to pile water up against the mid-Atlantic coast.  This is due to Earth’s rotation (and the “Coriolis Effect”), which causes the net flux of water to move to the right of the wind direction.  As Sandy itself approached the New Jersey coast, higher atmospheric pressure (black lines) pushing down outside the circular center of the storm helped force water to rise under the center of the storm, where the pressure is lower. This is the “inverse barometer” effect.

Next up is an animation of Sandy’s winds, pressure and total water elevation, which is the storm surge plus the tides and plus anything else such as rainfall or river-driven freshwater flooding.  This surge modeling is on a nested smaller grid that receives inputs from the larger scale grid at its boundaries.  The smaller grid is the NYHOPS grid, used for our regular regional forecasts of storm surges and ocean conditions.  The simulation is based partly on GFS atmospheric forcing, but mainly on the best forecast we could find – a Rutgers WRF model forecast (by Greg Seroka and Louis Bowers).

Click to see an anmation of water elevation (color shading) in the New York City, New Jersey and Long Island region. Also shown are wind velocity vectors (arrow) and isobars.  The right panel shows a zoom to the NYC region.  The axes on the top right show water elevation at The Battery over four days.

Click to see an animation of water elevation (color shading) in the New York City, New Jersey and Long Island region. This simulation includes both storm surge plus tides.  (NOTE: Time is in GMT here, four hours later times than EDT. Fixing that …)  Also shown are wind velocity vectors (arrows) and white lines are isobars. The right panel shows a zoom to the NYC region. The axes on the top right show water elevation at The Battery over four days.  The methods used for this simulation are very similar to a recent peer-reviewed published paper.

Now that we have created simulations with good accuracy, we can show people a new perspective on what happened, and we can also do experiments on Sandy to better understand hurricane storm surges and better forecast them in the future.  Beyond that we can even use the storm surge modeling to test out adaptations that reduce or prevent flooding, as we’re doing for the federal HUD’s Rebuild by Design competition.

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