The Corps and the Shore

The subject of this book is the activities of the US Army Corps of Engineers in beach stabilization efforts along the US coast over the last 150+ years, although the bulk of the material is more recent. The main author, Orrin Pilkey, was, at the time the book was published in 1996, a coastal geologist at Duke University.

Pilkey outlines the general problem he sees with Corps activities, then explores examples from around the country to highlight problems in the bulk of the book. He concludes the work by suggesting ways for the Corps to better serve the general public. And, while the restructuring would probably prove to be helpful, that's not usually the way government entities work - at least in my experience.

The bulk of the "science" contributed by Pilkey is that coastal stabilization is difficult. Thus, the best alternative is to allow the beaches to move as they would naturally. I don't disagree. But, people who have built structures adjacent to the beach do not want their structures to fall into the water. And, they'd rather not move them (in some cases, moving them isn't really a good alternative). So, what are the options? Hard stabilization (sea walls, jetties, groins, breakwaters, etc.) or beach replenishment. But, essentially, we have another "Control of Nature" fiasco on our hands. Essentially, you can try, but you'll give up before nature does.

There is a reason a beach is moving seaward or landward, just as there is a reason a glacier is advancing or retreating. If the beach is disappearing, it's because more sand is being taken from the beach than is being deposited in that location. It's not real complicated. So, if you construct groins (rock walls perpendicular to the coast) to trap sediment being transported by longshore currents, you will be robbing someplace downstream of the sediment that should be leaving your location. While you may have fixed your problem, you've passed the buck.

Coastal engineers attempt to come up with solutions to the problems, but they aren't really equipped properly. But, I think Pilkey is too critical of the coastal engineers and not critical enough of the scientists and society. The blame continually goes to the Corps for this and that, which isn't unfounded. But, if people weren't asking the Corps to save their beaches or improve their navigation channels, etc., they wouldn't have to try to come up with a solution. And, if the appropriation process wasn't as it is, they might not be as apt to fudge numbers for the cost-benefit studies as Pilkey accuses them of being. Apparently, for a project to be funded, the Corps has to demonstrate a positive cost-benefit ratio. That is, the cost has to be less than the value added by doing the project. If the numbers were computed correctly, would this happen often?

Pilkey claims that the engineers don't understand the complicated dynamics of the near-shore surf zone. And, he claims that the models don't do a good job of accounting for all the processes. Well ... duh! That's why it's a model. It's not a direct numerical simulation. But, it is true that it is a very difficult problem to tackle, even 10+ years later. I'm not sure how sophisticated sediment transport equations are. And, even if you have those perfectly figured out, you still need to be able to account for all the sand, mud, rock, etc. features in the system. So, you need very detailed bathymetric and soil characteristics. And, you also have to have a very high resolution 3-D coupled hydrodynamic/wave model. And, even if you had all of that, you would have to have some way to figure out the meteorologic forcing. And, since sediment transport and deposition is a cumulative process, even if you the exact specifications of a storm that is going to hit the area, if you don't know what the weather is going to be between when you collect all the data and start the model and when the storm comes, the initial conditions pre-storm won't be exactly correct. And, as they say, "Garbage in equals garbage out." In 2009, I don't think modeling the system is feasible. I don't think it would be possible in the next 10 years either. So, in the 1980's? Hmmmm.

I found the book to be interesting, although, at times, the tone was a little bit irritating. But, generally, the follies of the Corps (including at Folly Beach, South Carolina) and the people requesting the projects are entertaining. However, the whole book is a bit depressing when you consider all of the federal money that is being wasted. And, even more depressing, is that there isn't an end in sight.