Monday, February 23, 2015

Trends in Beach Nourishment


The folks at the Program for the Study of Developed Shorelines (who maintain the Beach Nourishment viewer highlighted in my last post) have kindly shared some data with me.  Below are a couple of graphs analyzing their data.  

I am grateful for their taking the moment to chat with me and a beach nourishment 101 explanation.  Any error in interpretation here is mine alone.  

The Beach Nourishment viewer keeps track of nourishment "episodes."  This is different from projects.

The US Corps of Engineers (USACE) is responsible for most beach nourishment projects.  When they propose a project to Congress for funding the entire project may contain many episodes.  For instance, the hypothetical "New America Beach Project" includes three episodes in which sand will be placed at the June, July, and August Beaches.

As well, this data contains episodes that include navigation projects in which dredge material from a channel was put on a beach.  USACE does not consider such methods as beach nourishment just navigation.

So, some differences in definition exist depending on where you get your data and you you talk to.

The first graph shows number of beach nourishment episodes indexed to the average number per year.  Clearly, there is an increase in the number of beach episodes each year over time.

It is generally accepted that the first beach nourishment project was on Coney Island in 1923.  This was done at the expense of local government to build up tourism to the area- the project allowed for the famous Coney Island boardwalk..

But beach nourishment didn't really get going as public policy activity until the 1950s.

In the past (though perhaps not so much today), most nourishment projects were characterized as flood control measures.  Around the 1950's the federal government began receiving a lot of pressure to step in an help out with disaster relief and prevention.  I am under the impression that this is why one sees an amp up in nourishment projects around the same time.

Thus, I divided the data in the top graph into a smaller subset in the bottom graph. The year 1955 is an arbitrary start point for 'some time in the 1950's'.  



Over the entire dataset there is an average of 21.6 episodes per year.  Some years see a tripling and many years are around 50% -100% above average.  

Over the 1955-2014 time period there is an average 31.3 episodes per year.  The number of projects varies by about 50%, give or take, around the average with some years seeing a doubling of episodes.  
Roughly the same can be said for the total cost per year in the next set of graphs (regardless of government cost share).   

Since 1955, the average annual cost of episodes is about $196M.  Since about 2000, there appears a generality that most years are about 50% more than the average with a couple years at twice the average annual cost.















The final graphs in the series show the annual cost per year of episodes as a percent of national GDP.

It also shows a bit why I became more curious about the 1950's affect.

The average cost of beach nourishment as a percent of GDP over the entire time series is ~0.003%.

The top graph shows that over the whole data series, the annual cost of nourishment projects has a percent of GDP has decreased.  But notice that some early episode years, when the economy was much smaller, the total cost constituted much larger percentages of GDP.

After the WWII our economy grew substantially.  Since 1955, the cost of beach nourishment as a percent of GDP shows no trend.


I don't know what this means, if anything, for policy or society.  

However, what the data seems to demonstrate is that the nation spends an increasing amount of funds on beach nourishment but this total amount is bound by economic growth (as measured here by GDP).  As a constant proportion of GDP, so long as the economy grows, perhaps funding for beach nourishment will too.  

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