pecipe for erosion 



torm as they explored every crevice of the coast 

 T H mapped its features foot-by-foot. 

 I three Sea Grant researchers have learned a 

 . about how the coast protects itself from erosion, 

 >t tat people can do to help the coast protect itself 

 a j ,vhy certain areas are more vulnerable or 

 i sistant than others. By the time the three are 

 l ug h next year, they hope to be able to tell local 

 X jcials and landowners in detail exactly what is 

 .opening on the coast and why. An erosion in- 

 ,jity scale— sort of a layman's guide to reading 

 shore— is being developed to help people on 

 t coast predict the erosion of specific areas and 

 |,„ for the future. Riggs, Bellis and O'Connor 

 ,pe to be able to impart enough knowledge about 

 : osion to let coastal residents work with an under- 

 jndingof the shores. 



Different rates for different banks 

 Riggs, O'Connor and Bellis have already dis- 

 jvered that different shorelines experience differ- 

 Dt rates of erosion and they have identified some 

 ujor shoreline types. The sand and clay banks 

 ,clude low banks of one to five feet which are 

 loderately to highly susceptible to erosion but can 

 t protected fairly easily. High banks of five to 20 

 et may be extremely erosion-resistant if they're 

 lade of tight clay or iron-cemented sand. If they're 

 Dt, the high banks are subject to the same sort of 

 osion as low banks. Bluffs rise higher than 20 

 Et and erode somewhat more slowly. They lose 

 lore material per foot, though, and are very diffi- 

 ilt to protect. 



Swamp forests have negligible erosion and sedi- 

 ent berms are actually accreting. The area be- 

 leen swamp forests and low banks erodes less 

 lan the low banks but more than the forest. The 

 ass marshes with their soggy peats are the most 

 odable but they protect the sandy soils behind 

 lem. 



Erosion of these shores is affected by numerous 

 her factors, which the researchers are still trying 

 unravel. So far, they've found that height, soil 

 imposition, water depth and offshore topography 

 front of the shore and the direction it faces all 

 fluence erosion. The type and density of vegeta- 

 >n on and in front of the bank, the breadth of the 

 nk and the size of the body of water the bank 

 era also affect the rate. Man's activities can 

 hibit or encourage erosion. 



The University of North Carolina Sea Grant 

 College Newsletter is published monthly by the 

 University of North Carolina Sea Grant College 

 Program, 1235 Burlington Laboratories, Yar- 

 borough Drive, North Carolina State University, 

 Raleigh, N.C. 27607. Vol. 3, No. 11, November, 

 1976. Dr. B. J. Copeland, director. Written and 

 edited by Karen Jurgensen and Johanna Seltz. 

 Second-class postage paid at Raleigh, N.C. 27611. 



Eroding peat marsh 



The options 



"There's no way to stop this process, but you 

 can slow it way down, so it's almost negligible to 

 the landowner," ECU geologist Stan Riggs said. 

 "One thing we're learning is that there is a whole 

 series of different natural mechanisms which 

 naturally slow erosion. Cypress, for example, can 

 naturally produce a buffer against waves and 

 catch sediment. 



"One of the big problems is that most people 

 who develop second homes are interested in clear 

 views and a big swimming beach. So the first thing 

 they do is cut down the cypress that block the view 

 and clean up the grasses so they can have a sandy 

 beach. Both the cypress and the grasses are natural 

 protections. So pretty soon, the property is reced- 

 ing at a major rate, which is a major economic loss. 

 So the people have to build a bulkhead, which is a 

 major investment and which, had they understood 

 the system, wouldn't have been necessary." 



Another common mistake, according to the three 

 researchers, is to clear the debris in front of an 



(See "The Real Solution," page k) 



The real solution . . . 



(Cont.from page S) 



eroding shoreline. The "trash" of fallen trees and 

 branches breaks the waves and acts as a natural 

 groin catching the sediment that erodes from the 

 bank. It should be left, at least until some other 

 type of bulkheading is made. 



"Clean it up and you're costing yourself several 

 feet of shoreline erosion," O'Connor said. 



The shoals that often form in front of an eroding 

 shore should also be left because they, too, slow 

 erosion. 



Sea Grant researchers are now looking at ways to 

 copy the coast's natural protections. But the most 

 common reaction to erosion — besides despair — is 

 still to build a bulkhead. Between May 1975 and 

 June 1976, requests for permits were made to build 

 more than seven miles of bulkheading along North 

 Carolina's estuarine shore — an investment con- 

 servatively estimated at at least three-quarters of 

 a million dollars. 



O'Connor, Bellis and Riggs have found that 

 where built well and with an understanding of the 

 process of erosion, bulkheading, sea walls, groins 

 and other man-made erosion barriers are effective, 

 especially on low-bank shorelines. They have also 

 found, however, that bulkheads should be placed 

 as planned units because the coast erodes in dis- 

 tinct geographic sections. Coves between resistant 

 clay bluffs, for example, will erode together and 

 should be treated as one shoreline. Otherwise, pro- 

 tection for just one part of the shore will only en- 

 sure greater erosion next door. 



Advantages and disadvantages 



Slowing erosion may make some landowners 

 happy, but it also has its disadvantages. It may 

 mean the loss of sandy beaches. Erosion provides 

 the sand that makes the beaches in the estuaries, 

 Riggs explained. Slow erosion and you risk cutting 

 off the replenishing sand supply. 



"Everyone wants a beach, but there's not a lot 

 of sand in the estuaries. So at some point you can 

 do yourself in." 



Slowing erosion may also hurt the seafood in- 

 dustry since erosion of the peats in the marshes 

 is probably an important means of recycling car- 

 bon and nutrients for the salt marshes. If you slow 

 erosion too much, you risk cutting the productivity 

 of the salt marshes which feed many of the com- 

 mercially important seafoods which, in turn, feed 

 the fishermen of the coast. 



One answer to erosion problems is to "let 'er 

 rip" and move development out of the way. Many 

 counties are now trying to figure out "setback 

 lines" beyond which it would be illegal to build. 

 The problem with setbacks, according to O'Connor 

 and Riggs, is that it is very difficult to choose the 

 line since different areas of the coast erode at 

 different rates. They hope their final information 



A common error: clearing a stable shoreline 

 and making it vulnerable. 



will reveal where setbacks could be set since their 

 data should show where development could occur 

 most safely. 



Still another suggestion is to make the natural 

 erosion barriers — cypress headlands and fringe, 

 resistant clay bluffs, swamp forest, peat marsh- 

 land — areas of environmental concern under the 

 Coastal Area Management Act. This would mean 

 any development there would have to meet state 

 guidelines. 



"We're not taking any stands on whether to 

 bulkhead or to let nature take its course," O'Con- 

 nor said. "But we can show what is likely to hap- 

 pen in an area and assign success probabilities to 

 different modifications. And we can provide an 

 education for people which can allow them to make 

 the right decisions. I've always maintained that 

 people who are informed tend to make the right 

 decisions." 



Losing ground 



