The Coastal Engineering Challenge: Impacts to Captiva and Remedial Actions — Hans J. M. Wilson, PE

Rising Sea Level on the Florida Gulf Coast and What Can Be Done About It

South Seas Resort, Captiva Island January 13, 2017

Image: LEEPA

Sea Level Rise – Captiva Island 1/13/16

In 2007, the Intergovernmental Panel on Climate Change (IPCC) stated that it is most likely human-induced (anthropogenic) warming contributed to the sea level rise observed in the latter half of the 20th century. The 2013 IPCC report (AR5) concluded, "there is high confidence that the rate of sea level rise has increased during the last two centuries, and it is likely that GMSL (Global Mean Sea Level) has accelerated since the early 1900’s.(Wikipedia)

Sea Level Rise – An Engineers Perspective

1. Fundamentals. 2. Looking at it from the ground up. 3. Slow insidious increase is imperceptible in today’s

world of immediate results. 4. Fortitude and the long view, it’s political folks. 5. What are the most immediately noticeable changes

that are not natural? None, it’s all nature in action. 6. A natural response to a manmade impact. 7. Do we need to panic? Depends on your timeline.

Fundamentals - Who Said What

Randall Parkinson (Space Coast Climate Change Initiative) & Jim Titus (EPA Climate Change Division)– “Climate change effects on boating in Florida’s coastal and inland waterways” ; Stem to Stern II – May 15, 2012 Clearwater Beach, Florida

0.13 in./yr. or 0.011 ft./yr.

Fundamentals – Skeptics with a C

Leon Ashby, President “The Climate Sceptics” – “Why an Emissions Trading Scheme (ETS) is not necessary”

Fundamentals – Maritime Engineers

Duncan Mellor – “An Update & Analysis of Climate Change & Rising Seas” ; Maritime Reporter & Engineering News; October 2016

Altimetry Trend 2.88mm/yr.-0.11in./yr. - 0.009ft./yr.

Fundamentals – Coastal Engineers

Todd L. Walton Jr. and Robert G. Dean – “Thoughts outside the bubble on Sea Level Rise” . FSPBA Shoreline 2010

Sea level rise @ 2mm/year from 1900-2000

0.82 ft. 1.01 ft. 1.14 ft. 0.88 ft. 1.11 ft.

0.015 ft/yr. - 4.6 mm/yr.

Impact on Coastal Processes

From Jim Houston and Bob Dean – FSBPA Conference 2016

Coastal Processes - Not So Simple

From Jim Houston and Bob Dean – FSBPA Conference 2016

Sea Level Rise – 2080

The short answer is, you won’t. The incremental increases by millimeters in elevation on an annual basis will be almost imperceptible. From the beach front or coastal perspective, there is typically sufficient height along the coast that adjustments can be made to the beach profile to adapt to the sea level rise. However, when contrasted with the impacts from storm driven surges and wave setups in multiples of feet, the sea level rise is inconsequential on a short term basis.

How Can I See It?

The Coastline View

What will I see? The long answer is incremental, almost imperceptible changes in lower lying areas. The canaries in the coal mine are: - increased salt water intrusion into wells (partly attributed to upland impacts) - coastal flooding - decreased efficiency in septic treatments. It will begin below the earths surface along the lowest lying coastlines, with properties having infrastructure (i.e. roads, septic systems, stormwater treatment, wells) in close proximity to coastal waters.

Typical Interior Coastline

Impacts to: -- Septic Drainfields -- Irrigations Wells -- Stormwater Mgmt Discharges

-- Street Drainage -- Seawalls, Coastal Structures -- Natural Resources

The Solution? At What Cost?

Intermediate Opportunities Septic Drainfields (and tanks) – Renovate or relocated to higher elevations; implement performance systems that do not rely on percolation into the substrate; install central sewer (better for the environment). Irrigations Wells – Relocate; implement desalinization features; utilize re-use water; landscape with native vegetation that does not require irrigation. Stormwater Management Discharges – Redesign and enhance berm heights; modify discharge weir elevations. Street Drainage – Raise the road bed; install one way gates at discharge outlets; re-route to higher ground. Seawalls – Place stabilizing materials immediately landward of the seawall cap to address wave overtopping; remove and replace with living shorelines that can “walk” inland as the mean high water encroaches. Natural Resources – Anticipate loss of resources as the natural process of adaptation runs headlong into human impacts.

Thank You!

Hans Wilson, P.E. Hans Wilson & Associates, Inc.

1938 Hill Ave. Ft. Myers, FL 33901

239-334-6870 hans@hanswilson.com

Caloosahatchee River Bridge - 2015 Caloosahatchee River Bridge – 20??