5 March 2013 – Conference on Sea Level Rise

Back in 1996 I was part of a team in charge of assessing the vulnerability of a major south Florida hospital to hurricanes. My specific responsibility was to characterize the potential impacts of hurricanes, and its various damaging components, on the facility located in the coastal region of Miami-Dade County and to identify and recommend specific mitigation measures to reduce the potential for damage to this facility from recurring hurricanes.

In researching the possible impacts of storm surge on the campus of this facility I was soon confronted with the reality of sea level rise. All of the available site plans, land survey and plans showing ground floor elevations for the various buildings made reference to elevations above NGVD, which was a fixed mean sea level reference point established in 1929. My research of tide gauge data  and other sources showed that mean sea level in 1996 at that specific location was already approximately 20 – 22 centimeters (~ 8″-9″) above NGVD, which meant all of those ground and ground floor elevations on the plans were that much lower with respect to mean sea level, and consequently more vulnerable to the impact of storm surge during hurricanes.

A constant frustration as I became much more involved in all aspects related to climate change, global warming and sea level rise, has been the persistent reference by scientists to sea level rise in terms of a rate of rise of 1 mm, or 2 mm per year, and more recently 1″ (or 2.5 mm) per decade, which has usually led to yawns, rolled eyes and just plain lack of interest from various audiences. After all, 1 mm is more or less the thickness of a penny, so even when you stack-up 2 or even 3 pennies they do not amount to much. How can we pretend to convey the seriousness of the threat posed by sea level rise in those terms?

I have found it to be much more effective to discuss sea level rise in terms of its horizontal component or what I call sea level run. In considering this aspect of sea level rise it is useful to imagine  a staircase. Each step in a staircase has a vertical dimension known as the rise and a horizontal dimension known as the tread or run. Most everyone will understand this analogy and find it quite logical that in order for a stair case to climb from one floor to another it must also travel a considerable horizontal distance. It is exactly the same for sea level rise.

Rate of SLRPowerPoint Presentation

Sea level run is a function of the slope of the beach and coastal region at a given region, but in general terms and considering the very low and gentle change in elevation prevalent in Southeast Florida, it is estimated that sea level run in this coastal region may range from 150 to 200 times the rise. Viewed in these terms, suddenly 3 mm is equivalent to 3 x 200 = 600 mm (approximately 2 feet) of  shoreline retreat per year and a new perspective takes over when considering the potential for damage from this hazard.

Things become even clearer when one considers how sea level rise and sea level run have been and will continue to exacerbate storm surge for the foreseeable future gradually transforming it into a much deeper, faster flowing, much more damaging hazard that also results in higher waves and vastly stronger energy of impact against buildings in its path.

To address what sea level rise is, what causes it, how fast it is occurring, how it will affect us, and what can we do about it? This past 5 March 2013 I gave a conference on Sea Level Rise: Can we keep the sea away? at the St. Gregory’s Episcopal Church in Boca Raton, Florida. The slides I used to illustrate my conference are now posted on this site. Please go to the CONFERENCES-PRESENTATIONS on the banner menu above and look for Sea Level Rise Conference – 5 March 2013, Boca Raton, Florida.

The National Climate Assessment 2013

A presidential directive by President George H. W. Bush in 1989 created the U.S. Global Change Research Program (USGCRP) as a venue for informing the Executive Branch of Government about potential consequences of climate change in the United States.

In 1990 the Congress mandated the USGCRP become an official federal program when it enacted the Global Change Research Act of 1990 (P.L. 101-606) with a mission of conducting or guiding a comprehensive and integrated U.S. research to assist the Nation and the world to understand, assess, predict and respond to human-induced and natural processes of global change.  The name of the program was changed to the U.S. Climate Change Science Program during a period from 2002  to 2008.

By law the USGCRP is required to submit a report to the President and the Congress every four years assessing current conditions based on scientific findings, and projecting major trends for the next 25 – 100 years. This report is known as the National Climate Assessment  (NCA) and it is the product of a national effort with participation from researchers and stakeholders from across the Nation, which also involves a period of public comments. open to all residents of this country.

The first assessment report was submitted in early 2000. The second NCA was submitted in 2009. The process for the third NCA was initiated in 2012 and continues today in 2013 with the period of public comments that will remain open until April 2013.

I had the  privilege of actively participating in the first assessment completed in 2000 as managing director for a regional workshop of the potential consequences of climate change on the U.S. Coastal South Atlantic and U.S. Caribbean Region hosted by Florida International University in North Miami Florida, in July 2008. In  my capacity of managing director for this workshop I wrote a white paper – The Need for Action to Confront Potential Consequences of Global Climate Change on a Regional Basis: a White Paper in support of the Climate Change and Extreme Events Workshop, (you may view this paper by clicking of this link WHITEPAPERDraft1 ) that set the  topics of discussion and objectives for the conference.

I also participated in the 2009 NCA by providing extensive written comments to the draft version of the report, and I am doing the same for what will be the 2013 report. Relative to this contribution by way of comments on the document I have also offered opinions and comments to some of the designated authors of the NCA. Following below is the text of a memorandum I sent to one of the NCA authors back in February of 2012, which is specifically relevant to the vulnerability of Southeast Florida to potential impacts driven by climate change. I believe those of you who reside in Southeast Florida or in similar coastal regions may  find this document of interest, and quite relevant to conditions in your own communities:


TO          :           

FROM   :               Ricardo A. Alvarez

REF         :               National Climate Assessment

DATE      :               24 February 2012

This is in response to your email of 23 February 2012, regarding the in-progress national assessment of climate change, and the two questions you posed therein.

My current thinking relative to your questions is summarized below:

Critical Issues

  1. Erosion and loss of sand supply [the economic value of sand as a resource]:

There are approximately 800 – 850 miles of sandy beaches in Florida, of which around 450 – 500 miles are already designated as being in critical condition due to erosion, loss of sand, the disruption of the natural flow of sand, and the lack of a reliable off-shore or inland source of sand for nourishment. Many of these sandy beaches are on the water-front of heavily built up large urban areas in the coastal region.  

Current and future adverse consequences on this economic resource from the impact of sea level rise raise the potential for severe economic damage affecting hundreds of thousands of jobs in Florida and other coastal states in the Southeast region.

2. Developing reliable source of data on velocity of storm surge flow:

Based on the extreme loads that it generates and the potential for damage to the built-environment and transportation infrastructure, hydrodynamic pressure and wave impact associated with storm surge are by far the most damaging hazards associated with tropical cyclones. Given the exacerbation of storm surge by sea level rise, such potential for damage will likely continue to increase in the future. 

In view of this high risk it is quite worrisome that we lack a reliable source of data on the expected velocity of flow of storm surge, which is specific for the various coastal urban communities in the southeast. Velocity of flow is the key driver for resulting hydrodynamic and impact forces generated by storm surge.

There is a critical need for research and models to build such database for storm surge velocity of flow, that will allow for the characterization of impacts on the built-environment and transportation infrastructure; a necessary first step in the design of adaptation solutions.

3. Incorporating Atlantic multi-decadal oscillation into climate models:

Previous versions of the National Assessment relative to the Southeast region list the likelihood of increased hurricane intensity, rainfall intensity, and storm surge height and strength.

Although the NA makes references to studies and sources that support these assertions, the reality is that the scientific community continues to be divided on both sides of this issue. Ongoing scientific debate is also divided with respect to the actual linkage between climate change and tropical cyclones.

Given the current state of scientific lack of consensus on this issue, it is critical that higher resolution climate models continue their attempts at discerning cyclogenesis driven by climate change. This research also needs to include the Atlantic multi-decadal oscillation, which alternates between periods of increased and depressed annual tropical cyclone activity in the Atlantic basin, and which during its current high activity phase may be masking the linkage between tropical cyclones and climate change.

The successful inclusion of the multi-decadal Atlantic oscillation as a critical component of climate models, would allow those working on adaptation gain a better informed understanding of future scenarios resulting in a more effective approach to identifying solutions for adaptation.

4. Modeling exacerbation of storm surge:

Given the potential for damage from this hazard, which will grow as it is exacerbated by sea level rise in the future, it is critical that at-risk communities along the coastal region in the Southeast, develop  the capability for characterizing future impacts  of storm surge on the built-environment and transportation infrastructure.

Development of such capability will play a major contribution in the design and implementation of adaptation measures, or the identification of alternative courses of action.

Toward this objective it is critical that models capable of reliably simulating the exacerbation of storm surge over time, on a basin or location specific basis, be developed and made available as tools for the design professionals and urban planners. Such models must be dynamic in the sense that with continuing sea level rise, the behavior of future storm surge and it potential impact will change in response to such conditions.

5. Identifying  feasible and effective ways for keeping the ocean away:

The NA has concentrated in identifying what is probable and what is possible by way of issues, and hazards that may affect communities in various regions.

This approach has contributed a foundation of knowledge for others to use in devising future scenarios to identify effective adaptation measures for the built-environment and transportation infrastructure.

Relative to this it is critical, for the protection of coastal communities, that a more dynamic and proactive approach be used in identifying effective solutions for keeping a rising ocean away. This proactive approach must also include research into solutions to existing or perceived problems that may impede the deployment or construction of protective measures on community-wide or regional scales.

One specific example is the possibility of using off-shore structures to keep the rising sea away from specific coastal communities, where the geology of the hard bottom or substrate that may provide a foundation for such structures may not be suitable for such a job. In the case of southeast Florida for example, it appears the underwater substrate consist of porous rock, which would still allow for water seepage even after protective barriers and structures are erected.

While this may be a valid argument, it is critical that research be directed at identifying effective ways of solving such problem, perhaps by means of developing injection or other methods to make such rock substrate impermeable. Otherwise, precious time is being wasted by repeatedly stating the obvious without looking for possible solutions to the problem. The criticality of this issue is compounded by the fact that any project of this type, involving underwater resources, may require many years for all of the studies and permitting to be resolved before actual work can start. If regular beach nourishment projects require up to 12-15 years of administrative work and permitting before they can be implemented, when federal funds are used, it might be possible that more complex projects, involving building structures to keep the sea away, could take 25-30 years before actual construction begins. Consider how much the sea will rise and storm surge be exacerbated during this time.

Most Important Risks

1.       Storm surge impacts:

There is huge potential for damage to the built-environment and transportation in coastal communities in Southeast Florida.  Such potential for damage continuously increasing over time as additional rise in sea level contributes to higher, faster flowing storm surge.

2.       Extreme precipitation events:

The possibility of extreme rain events (heavy precipitation over a short span of time) causing increased environmental loads on structures and roofs, which may exceed design criteria leading to potential structural damage.  Also the associated potential for increased flash-flood events.

3.       Soil saturation:

Coastal flooding either from storm surge or flash floods associated with extreme rain events, and also a rise in the water table, may result in extended instances of soil saturation with the potential for damaging buildings’ ground slabs, foundations or underground spaces, because of hydrostatic pressure.

4.       Structural damage due to erosion:

Erosion may lead to undermining of building foundations with considerable potential for structural damage.

5.       Damage to infrastructure from salt water:

Specific infrastructure in the coastal region, such as ground-mounted electrical transformers and switching equipment, can be adversely affected by salt water during coastal flooding events or just salt water intrusion into the ground, due to the corrosive action of salt water when in contact with such equipment.

Also, electrical distribution or transmission lines near the coast, including transformers, and even line insulators,  can be damaged by mist and spray from the sea leading to salt coating the equipment, inducing electrical arching, and also corrosion.  The possibility of this increases with sea level rise as the sea gets closer to such equipment.

6.       Loss of effectiveness of water management infrastructure:

In many locations along the southeastern coast water management operations have little to work with when it comes to a gradient to drive gravity flow of water. As sea level rises and infiltrates further inland that gradient is reduced even further, and the balance between the head of fresh water and incoming salt water becomes progressively more difficult to maintain.

This reduction in the effectiveness of this installed water management infrastructure can catastrophic consequences when it comes to hurricane and storm surge impacts, or instances of extreme rain events resulting in flood events. The potential for damage to the built-environment and transportation will continue to increase as the effectiveness of the water management system decreases.

Your comments regarding above material are welcome either directly on this site or via email, at your convenience.