Environment, Coasts, Oceans, & Infrastructure

As a retired professor, I am currently VP of the Hollywood Lakes Civic Association which is starting to collect info on sea level rise and is experiencing periodic tidal flooding of streets and property. Current seawalls are nonuniform, some in disrepair, and not in all flood-prone areas.
Would like to start to obtain references and information on effective sea wall designs for our muck-and -mangrove environment to begin a grassroots assessment effort and civic education. Input would be useful in speeding up our activities. An allied issue is that South Florida is subject to periodic tropical storms and resultant storm surge which can reach six feet, hence seawalls should also provide some protection for this surge while protecting against monthly tidal surge. Our current minimum seawall height of 3.5ft above MHT is generally viewed as inadequate given a sea level rise of about an inch a year. References would be appreciated.

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Alexis Sommers Ph.D., A.M.ASCE
Professor Emeritus
University of New Haven
Hollywood FL
(754)816-5648
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We have been successful in using Steel Sheet Piling for these types of surge
in places like NY for protection of Electrical Substations albeit a bit higher
walls than 6 feet....some of which required Cover Plates or Combination Walls...

Be happy to discuss...



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Richard Morales, M.Sc., P.E., F.ASCE
Director of Engineering
LB Foster Piling
Atlanta GA
(404) 275-6430
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Alexis
I suggest that you make contact with the ASCE/COPRI Waterways Committee, as any form of barrier to vessel traffic (which would affect intracoastal navigation) would be of interest to them. One of their current projects is looking at the preparation of a rehab manual for navigation structures. It is an applied guide to practitioners for what to look for or to avoid when they are performing a rehab project. With ASCE becoming a major advocate in sustainability/resiliency in US, what is intended is this manual is any recommendation to practitioners should consider sustainable/resilient materials of replacement for what did not work and the care for environment. It should furnish enough information to the users to make correct decisions.  The lessons learned, failed technologies, successful technologies, and successful and failed methods have a valuable place in this manual.  It will have less of theory and more of applied/practice procedures but unfortunately is a long way from being complete. Contact the chairman Kelly Barnes (Kelly.J.Barnes@...) for more information.

You might also take a look at the recent PIANC report of their Working Group 137, entitled ‘Navigation structures: their role within the flood defence systems – Resilience and performance under overloading conditions’.

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Graeme Forsyth CP, D.NE, M.ASCE
Senior technical consultant - Hydraulic gates
CH2M
Glasgow
440141 5522000 x2089
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In my experience in industrial shoreline settings in major ports and also in residential beach settings in Long Island, there are basically 2 types of seawalls in common use, steel sheet piling and composite sheet piling. Sometimes composite can be fortified with timber piles. Steel is required for wall heights greater than 15 to 20 ft. Below that, composite starts to become economical. Composite is also corrosion-proof which is a big plus. The wall heights you describe may well be within composite territory, especially if the subsurface is not too hard. Note that the additional wall height that might be required due to sea level rise or storm surge is imposing a lateral force in the opposite direction as the soil. So that additional height is not additive for determining internal stresses.

There are various types of composite sheet pile materials including vinyl, polyethylene, fiberglass, and more. One firm that comes to mind, called CMI, has a line of such sheet piling products. I have no affiliation with them. There are many others as well. Skyline Steel is a big supplier of steel sheet piling in the US. There are a few others. Again, I have no affiliations. 

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John Francescon P.E., M.ASCE
Hatch
New York NY
(646)
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If you would like to include the impact of the sea level rise in designing the top elevation of your seawall I suggest using an approach that allows a reasonable risk management. One such approach that I have been developing is called the equivalent risk method. Here is a reference to a presentation on this method:

http://www.floods.org/Files/Conf2015_ppts/E7_Zomorodi.pdf

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Kaveh Zomorodi P.E., M.ASCE
Senior Water Resour
Dewberry
Fairfax VA
(703) 849-0336
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The geology of south Florida provides special challenges in providing protection from sea level rise.  The limestone layers just below the surface soils are extremely porous.  Building a conventional seawall will not prevent the rising water levels from just seeping up through the ground.

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Richard Czlapinski P.E., D.CE, M.ASCE
Senior Coastal Engineer
Jupiter FL
(561)744-8410
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Original Message:
Sent: 02-10-2017 09:43
From: Kaveh Zomorodi
Subject: Design of effective seawalls for south Florida Intracoastal Waterway locations

If you would like to include the impact of the sea level rise in designing the top elevation of your seawall I suggest using an approach that allows a reasonable risk management. One such approach that I have been developing is called the equivalent risk method. Here is a reference to a presentation on this method:

http://www.floods.org/Files/Conf2015_ppts/E7_Zomorodi.pdf

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Kaveh Zomorodi P.E., M.ASCE
Senior Water Resour
Dewberry
Fairfax VA
(703) 849-0336
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Richard makes an excellent point.  You may need a cut off wall to make the sea wall effective.
Do you have a comprehensive geotechnical report?  How deep, and thick, is the limestone layer?

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Russell Barnes P.E., M.ASCE
PRINCIPAL
Wilshire Consulting Services
Napa CA
(707)8151707
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Original Message:
Sent: 02-10-2017 12:03
From: Richard Czlapinski
Subject: Design of effective seawalls for south Florida Intracoastal Waterway locations

The geology of south Florida provides special challenges in providing protection from sea level rise.  The limestone layers just below the surface soils are extremely porous.  Building a conventional seawall will not prevent the rising water levels from just seeping up through the ground.

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Richard Czlapinski P.E., D.CE, M.ASCE
Senior Coastal Engineer
Jupiter FL
(561)744-8410
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On taking account of the accelerated sea level rise (ASLR), I would also suggest to consult the 2014 USACE publication (Procedures to Evaluate Sea Level Change: Impacts, Responses and Adaptation). This document shows a wide margin of disagreements among various agencies in the projections of future ASLR. Despite the fact that all coastal states have their own assessments, uncertainties in ASLR projection could have significant consequences to stake holders in costs etc. In addition, uncertainties of associated enhanced storminess make the decision making even more cumbersome and risky.

For reflective seawalls scour and overtopping could pose a big problem – especially during storms. There are many publicly available guidelines including CEM addressing the issues.    

Dilip

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Dr. Dilip Barua, Ph.D, P.Eng, M. ASCE
Consultant - Coastal, Port and Marine Engineering
Vancouver, Canada
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