structures in the north Atlantic (Coast- 

 al Region 7), particularly along the New 

 Jersey and Long Island coastlines. No 

 information unique to groins in this 

 coastal region was found. 



Groins are used throughout the 

 Great Lakes (Coastal Region 8) to pro- 

 tect both shallow and steep, eroding 

 shorelines. The Michigan Demonstration 

 Erosion Control Program involves an on- 

 going study of the effectiveness of a 

 number of shore protection devices, in- 

 cluding groins (Brater et al. 1974, 1975, 

 Marks and Clinton 1974). Several dif- 

 ferent designs and materials are being 

 investigated. Some of the designs have 

 proved successful at retarding erosion 

 while others have failed. A great deal 

 has been learned concerning erosion on 

 Great Lakes shorelines. Filters are nec- 

 essary to prevent undermining or settl- 

 ing on clay and sand substrates (Marks 

 and Clinton 1974). Impermeable groins 

 are preferable for use in the Great 

 Lakes (Lee 1961). Basic design criteria 

 generally differ little from that of the 

 groins in the ocean. One difference is 

 that Brater (1954) recommends that 

 they terminate short of the 6 ft (1.8 m) 

 depth contour for maximum effective- 

 ness. 



BULKHEADS 

 Definition 



A bulkhead is a structure or parti- 

 tion built to prevent sliding of the land 

 behind it. It is normally vertical, but 

 may consist of a series of vertical sec- 

 tions stepped back from the water and 

 built parallel or nearly parallel to the 

 shoreline. There is no precise distinc- 

 tion between bulkheads and seawalls, 

 although some authors suggest the pri- 

 mary purpose of a bulkhead is to pre- 

 vent sliding of the land while the pri- 

 mary purpose of a seawall is to protect 

 the upland area from wave attack (U.S. 

 Artry Corps of Engineers 1973b). Thus, 

 a seawall might project above the eleva- 

 tion of the upland area, while a bulk- 

 head would terminate at or below that 

 elevation. 



Since bulkheads, seawalls, and re- 

 vetments are all generally parallel to 

 the shoreline and separate land from 



water areas, there is some confusion of 

 identification and the same structure 

 may have different names in different 

 areas. 



Structure Functions 



Bulkheads are built to prevent 

 sliding of the land behind the struc- 

 ture. In this capacity they serve a 

 number of diverse functions, such as 

 protection of uplands from erosion, 

 creation of shorefront real estate, 

 moorage of vessels, and other aesthetic 

 or recreational uses. However, the uti- 

 lity of bulkheads is that they allow 

 protection against waves and currents 

 without loss of land. Thus, one major 

 function of the structure is to deline- 

 ate between land and water with no loss 

 of land area. In many areas bulkheads 

 are built along shorelines and then 

 backfilled to create or reclaim water- 

 front land. Bulkheads are often used 

 where land is particularly valuable or 

 where there is insufficient land avail- 

 able to provide a sloped surface or 

 beach for protection. 



Bulkheads provide a vertical separ- 

 ation of land and water which allows 

 mooring of vessels adjacent to land 

 without the necessity of a pier. A 

 bulkhead, either alone or in conjunction 

 with a wharf, is often used for cargo 

 handling facilities in ports. 



Site Characteristics and 

 "Environmental Conditions 



Bulkheads are built parallel to and 

 on the shoreline. The location of a 

 bulkhead on the shoreline is generally 

 in the vicinity of the mean high water- 

 line, but placement can range from above 

 mean high water to below mean low water 

 depending upon the structure's function. 

 For example, when bulkheads are built 

 for boat mooring, the structure general- 

 ly is placed below the mean high water- 

 line and the bottom, in front of the 

 structure, is dredged to allow access at 

 low tides. Bulkheads thus are found in 

 all tidal zones ranging from subtidal to 

 terrestrial. They are generally install- 

 ed in areas of relatively low wave ener- 

 gy because waves will usually cause 

 scour and subsequent structural degrada- 

 tion. 



44 



