SEA LEVEL RISE AND FLOOD PROTECTION


Regardless of the causes, southeast Florida, with a population of 5.6 million (one-third of the State’s population), is among the most vulnerable areas in the world for climate change due its coastal proximity and low elevation (OECD, 2008; Murley et al. 2008), so assessing sea level rise (SLR) scenarios is needed to accurately project vulnerable infrastructure (Heimlich and Bloetscher, 2011). Sea level has been rising for over 100 years in Florida (Bloetscher, 2010, 2011; IPCC, 2007).  Various studies (Bindoff et al., 2007; Domingues et al., 2008; Edwards, 2007; Gregory, 2008; Vermeer and Rahmstorf, 2009; Jevrejeva, Moore and Grinsted, 2010; Heimlich, et al. 2009) indicate large uncertainty in projections of sea level rise by 2100. Gregory et al. (2012) note the last two decades, the global rate of SLR has been larger than the 20th-century time-mean, and Church et al. (2011) suggested further that the cause was increased rates of thermal expansion, glacier mass loss, and ice discharge from both ice-sheets. Gregory et al. (2012) suggested that there may also be increasing contributions to global SLR from the effects of groundwater depletion, reservoir impoundment and loss of storage capacity in surface waters due to siltation.

Why is this relevant?  The City of Fort Lauderdale reported last week that $1 billion will need to be spent to deal with the effect of sea level rise in Fort Lauderdale alone.  Fort Lauderdale is a coastal city with canals and ocean property, but it is not so different from much of Miami-Dade County, Hollywood, Hallandale Beach, Dania Beach and host of other coastal cities in southeast Florida.  Their costs may be a harbinger of costs to these other communities. Doing a “back of the napkin”  projection of Fort Lauderdale’s cost for 200,000 people to the additional million people in similar proximity to Fort Lauderdale means that $5 billion could easily be spent over the next 100 years for costal impoundments like flap gates, pumping stations, recharge wells, storm water preserves, exfiltration trenches and as discussed in this blog before, infiltration galleries. Keep in mind that would be the coastal number and we often ignore ancillary issues.  At the same time, an addition $5 to 10 billion may be needed for inland flooding problems due to the rise of groundwater as a result of SLR.

The question raised in conjunction with the announcement was “is it worth it?”  I suggest the answer is yes, and not just because local politicians may be willing to spend money to protect their constituents.  The reality is that $178 billion of the $750 billion economy of Florida, and a quarter of its population, is in the southeast. With nearly $4 trillion property values, raising a few billion for coastal improvements over 100 years is not an insurmountable task.  It is billions in local engineering and construction jobs, while only impacting taxpayers to the tune of less than 1/10 of a mill per year on property taxes. This is still not an insurmountable problem.

I think with good leadership, we can see our way.  However, that leadership will need to overcome a host of potential local community conflicts as some communities will “get more” than others, yet everyone benefits across the region.  New approaches to working together will need to be tried.  But the problem is not insurmountable, for now…

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