Category Archives: Storm Surge

April 2011: Extreme Weather Events

In the spring and early summer of 1998 I researched various sources to write a paper titled  The Need for Action to Confront Potential Consequences of Global Climate Change on a Regional Basis, to set the topics of discussion for one of the regional conferences taking place nationally as part of a National Assessment of Consequences of Global Climate Change in the United States [ or just National Assessment or NA for short] mandated by the U.S. Congress. The specific region for this conference included the U.S. South Atlantic coastal regions of Florida, Georgia, North Carolina, South Carolina and Puerto Rico and the U.S. Virgin Islands.

In writing this paper and conducting my research I was striken by the complexity and interaction of natural processes governing the behavior of the coupled ocean-atmosphere system, and the byproducts that become hazards with the potential for causing damage to life, all aspects of human activity and the environment in their paths.

Also significant to me was the realization that: (a) Our Earth’s climate is driven or affected by so many factors acting on time scales that vary from hours or days to millennia, and which in many cases conform to repetitive cycles; (b) While climate may be changing so slowly, almost imperceptebly, in response to a natural cycle lasting thousands of years such as changes in the orbital mechanics of Earth around the Sun and the galactic center, it also has the capacity for being puntuacted by localized extremes such as temperature or atmospheric pressure that lead to weather events that last from hours to days; (c) This contrast between extremely slow change and the turmoil of hourly or daily events requires Nature to constantly activate other components of the ocean-atmosphere complex seeking to restore equilibrium; (d) There is an inherent fragility in this struggle between extremes as climate is actually happening in that thin wispy vail of gases, the atmosphere, surrounding Earth where less than 3/100 of 1% of the component gases contribute to the conditions allowing multicellular – human – life to exist. It is simple to deduct how even minor changes may alter the equilibrium that Nature tries so hard to maintain, leading to potentially dire consequences and change perhaps even for life as we know it.

These findings influenced me not only in my writing of the white paper for the conference, but in naming the upcoming event the Climate Change and Extreme Events Workshop”. In retrospect, since this took place in 1998, I have to say the extreme event characterization was right on target as numerous weather events over the past 13 years have reinforced my ideas and findings expressed in the white paper mentioned above [which you can view by clicking here WHITEPAPERDraft1].

The above thoughts and reference serve as preamble to comments and illustrations I want to share relative to extreme weather events taking place in the United States over just a few passing days this April of 2011. You will find my comments on a brief paper under the title April 2011: Extreme Weather Events, which you can read by clicking of the following link:  April2011ExtremeWeatherEvents

Sea Level Rise in Florida

Back in 1995 I was a consultant to an architectural/engineering team that had been charged with evaluating the vulnerability of a major hospital, located near the coastline of southeastern Florida, to the impacts of hurricanes. The assessment of vulnerability had the objective of determining if there were practical alternatives for the hospital to exercise in lieu of the mandatory evacuation it faced in case a hurricane warning were to be issued by Miami-Dade County, which carried a mandatory evacuation order.

Evacuating a major hospital, as I discovered while I participated in that study, especially one where a large percentage of the patients require intensive care or are frail and elderly, is truly a major and critical undertaking. In addition, evacuation of a hospital raises critical issues of respnsibility for patient care, access to medical records, patient safety, and liability.

My participation in this project led me to propose “Sheltering-in-place”as an alternative to evacuation for major hospital vulnerable to the impact of hurricanes. This proposed alternative survived a rigorous process of debate and peer review involving professionals in several disciplines and representatives from the state and county governments, and in 1996 became the accepted paradigm in Miami-Dade County.

In approaching this assessment of vulnerability, I first gathered data to establish a baseline regarding the physical characteristics of the project site relative to the hazard impacts it faced as a result of its location. Data related to ground elevation, proximity to the ocean

and intracoastal waters, coastal bathymetry characteristics were gathered to paint a picture of what could happen at the site under the impact of a hurricane.

In the course of doing this I made one important discovery. Existing surveys and site plans for the hospital campus did not reflect the actual conditions of the place in 1995. To begin with the survey of ground elevations and elevation of ground floors of the several building on campus was based on NGVD (National Geodetic Vertical Datum), meaning mean sea level as it had been measured back in 1929. I realized then I needed to determine what these various ground and building elevations with respect to mean sea level were in 1995, so that we could take into account any changes in sea level from 1929 to 1996. Research of tide-gage records and several data sets maintained by NOAA indicated mean sea level at this location in 1995 was 0.23 meters above the 1929 NGVD.

This was a truly significant discovery for two main reasons: (a) it meant ground and building ground-floor elevations were 23 centimeters lower with respect to mean sea level than indicated in site survey and plan documents, (b) it also meant the potential impacts of storm surge and coastal flooding during hurricanes would result in higher water and wave heights. In summary, the hospital facility was more vulnerable to these impacts in 1995 that it would have been in 1929 if it had been built at that time. What truly made this a critically significant discovery was the realization that as sea level continued to rise in the future the potential impacts from storm surge, waves and coastal flooding would be exacerbated increasing the vulnerability of the hospital, hence its potential for damage under the impact of hurricanes.

My research at the time also showed that all available sources of data to assess the vulnerability of the site, such as flood maps and storm sure atlases were all based on NGVD 1929 and did not make any provisions for sea level rise. I also found that design standards, such as ASCE-7 (American Society of Civil Engineers – Standard 7), were also based on references to historical data of sea level and flood elevations and did not include methodology to make corrections to account for historical or future changes in sea level. Clearly this was a situation that needed to be corrected in order to arrive at more accurate estimates of potential damage to buildings and infrastructure from the impact of hurricanes.

It is now 2011, sixteen years later, and while some changes have taken place much remains to be done. Most land surveys and ground elevation studies are now using AVD-88 (the American Vertical Datum of 1988) as the point of reference and several data sources now exist that allow for far more accurate determination of current mean sea level as well as estimations of future mean sea levels at specific locations. Unfortunately the sobering reality is that design criteria for building and infrastructure design and construction have yet to incorporate provisions to account for the impacts of storm surge and waves and coastal flooding as these hazards continue to be exacerbated by sea level rise.

On a positive note it is good to see that here in Florida the state government and other entities are focusing on the potential impacts of climate change, publishing important studies and documents on these topics. The Florida Ocean and Coastal Council is one of such agencies, which in 2009 published “The Effects of Climate Change on Florida’s Ocean and Coastal Resources” a peer-reviewed document with the objective of educating the state legislature and the general public on what we know about these potential climate change impacts based on current state of science, what is probable and what is possible in term of potential impacts. I was one of the contributing authors to this study and worked on it during 2008 and 2009.

 A new peer-reviewed report also commissioned by the Florida Oceans and Coastal Council, “Climate Change and Sea Level Rise in “, has just been published ( click on following link to read this report, Climate Change and Sea Level Rise[1].) As with the previous study I was also a contributing author to this one together with several other Florida scientists and members of the council. My specific contribution was in the area of impacts to the built environment and coastal infrastructure, a chapter that was edited and coordinated by my good friend Karl Havens, Ph.D., from the University of Florida who is also Director and Professor of Florida Sea Grant College Program.

This report provides an excellent foundation for various sectors to identify adaptation alternatives, which may prove effective in reducing the potential for damage from the impact of hazards driven by or exacerbated by climate change. It is clear than in a state such as Florida, a narrow low laying peninsula, where must of the urban development and infrastructure is located on the coastal regions, sea-level rise exacerbated storm surge, wave impacts and coastal flooding constitute critical factors in the development of design-criteria for future buildings and infrastructure and for the retrofitting of existing facilities and built-environment if we are to have a chance of adapting to sea-level rise and its consequences in the future.