This is what a Terminal Groin looks like:
That's Captiva Island, Fla., (zoomable) a terminal groin example from a 2009 / 2010 N.C. legislative study on groins.
You can look at that and probably feel comfortable the groin is keeping sand in right behind it, even if some sand was trucked in.
Harder to predict is what that wall does, say, half a mile away. And sand along the N.C. coast is kind of a zero-sum issue, since people's houses are surrounded with sandbags and will probably fall into the ocean soon.
A House legislative committee ordered a study on groins in 2009, hoping to determine whether lifting N.C.'s ban on them is a good idea. From the Winston-Salem Journal:
Six months later the study was done. It was 530 pages long, cost more than $287,000 to produce and determined that it's "difficult to draw conclusions" on whether terminal groins work.Now, parts of that story were cut for space.
For example, one of the legislators who sponsored the bill requiring this study, state Rep. Lucy Allen, said it was "appropriately funded," then said she didn't read "any part of it."
Allen chaired the House Environment and Natural Resources Committee in 2009, but about the time the study was complete Gov. Bev Perdue appointed her to the state utility commission. That's why Allen didn't look at the study, she said.
The bill's other primary sponsor was state Rep. Pryor Gibson. Rep. Gibson said he wasn't happy the study didn't provide definite answers, but said groins were "way too big of an issue not to have the data collected."
But "organized" may be a better word than "collected" here. Given until April Fool's Day 2010 to finish the study, researchers reported back that due to "schedule and budget constraints ... no new data collection efforts were undertaken."
From study team's final recommendations:
Rather, available data (shoreline changes, nourishment and dredging activities, natural resources, etc.) were collected from as many sources as possible. Additionally, most of the data originally were collected for purposes other than determining the potential impact of a terminal groin. ...My questions to you: Do you think the state got a good price for this information? And was it reasonable to expect an answer to "take six months and tell us how these walls are likely to affect where the ocean puts sand?"
The Commission has concluded that the general impacts of the groins, as reported in this study, tend to be lost in the “noise” of other inlet management activities. ...
"Based on the results, the (study) commission cannot make a determination that terminal groins would or would not cause adverse impacts on the environment or adjacent properties."