S h o r e l i n e E r o s i o n Chapter 3: North Carolina Estuarine Shoreline Erosion Studies OVERVIEW they all come up with the same general erosion is severe in Pamlico Sound and is results and rates of recession. The studies ubiquitous throughout all subhabitats Numerous estuarine shoreline are briefly summarized below. (Table 3.2, page 39). erosion studies were previously done for portions of the N.C. coastal counties and REGIONAL STUDIES North Carolina Coastal Counties include the following: In northeastern North Carolina: Stirewalt and Ingram Pamlico Sound The USDA-SCS (1975) produced (1974); USDA-SCS (1975); Dolan and data for 15 coastal counties concerning Bosserman (1972); Hardaway (1980); Using 1938 to 1971 aerial photo- rates and types of estuarine shoreline and Everts et al. (1983). Bellis et al. graphs, Stirewalt and Ingram (1974) erosion (Table 3.3, page 40). Pender, New (1975); O’Connor et al. (1978); and evaluated the shoreline recession at 16 Hanover and Brunswick counties were Riggs et al. (1978) mapped 1,593 miles sites around the perimeter of the Pamlico judged to have minimal problems with of estuarine shorelines in the Albemarle- Sound (Table 3.1, page 38). Five of these estuarine shoreline erosion, and therefore Pamlico estuarine system. sites were situated on the backside of the were not included in their evaluation. Also, Hartness and Pearson (1977), barrier islands, and 10 sites were on Also, erosion processes along the back- summarized the estuarine shoreline shorelines that rim the mainland coast. barrier estuarine shorelines were consid- erosion in three southern coastal counties: The Stirewalt and Ingram (1974) ered to be beyond the scope of their Pender, New Hanover and Brunswick, study made no attempt to relate the study. Table 3.3 (page 40) summarizes the and established 10 sites in the Pamlico changing patterns of shoreline recession USDA-SCS (1975) shoreline erosion data River estuary as long-term erosion to the erosional processes (i.e., shoreline for 18 coastal counties. control sites. type, fetch, orientation, etc.) nor did they The USDA-SCS study utilized aerial Locations of these studies are present any methodology concerning photos from 1938 to 1971 to develop outlined on Figures 3.1 and 3.2. These their photographic techniques, source of average erosion rates. All of the data were studies are based upon analyses of old photos utilized or indication of how they based upon defining a series of reaches surveys, charts and aerial photos and vary arrived at their maximum annual erosion within each county that represented areas tremendously in scale — from specific rates. Consequently, I have re-evaluated of similar shoreline types, fetch and land small sites around Pamlico Sound to all their maps in an effort to maximize the uses. Consequently, all data presented in of the coastal counties, to a portion of the information concerning erosional processes. the study were severely generalized and back-barrier estuarine shorelines. Each shoreline segment is divided into a represent an average number over the However, none were done with the rigor type, including low-sediment bank, distance of each reach (the reaches necessary to represent anything other than swamp forest, and marsh based upon ranged from 0.5 to 39 miles in length), generalErosion Studies patterns of recession and either direct knowledge of the area or without any indication of the variability approximate erosion rates. It is interesting aerial photo analysis. These data are only in shoreline type, fetch, land use or to note that in spite of the lack of rigor, approximations to indicate that shoreline erosion rates that occur within the Next page: This actively eroding swamp-forest estuarine shoreline is along the south shore of Albemarle Sound. Page 28 Page 29 T h e S o u n d f r o n t S e r i e s FIGURE 3.1. Map shows the location of estuarine shoreline erosion studies in the North Carolina coastal system by other researchers. Page 30 S h o r e l i n e E r o s i o n reaches. Due to the techniques utilized in under the auspices of the North Carolina type. However, natural complexities and this study, the USDA-SCS (1975) Sea Grant College Program. Locations of variations of shoreline types occur within shoreline erosion data is extremely these studies are outlined on Figure 3.2. each coastal segment. Thus, due to the map general and should not be construed to be These estuarine shoreline erosion studies scale, only the dominant shoreline type exact erosion rates. consisted of physically mapping the within each coastal segment was mapped. geologic, biologic and hydrologic Outer Banks Back-Barrier character of the shorelines on: 1:1000 ALBEMARLE SOUND Estuarine Shoreline Erosion scale maps from shallow draft boats for ESTUARINE SYSTEM all coastal segments included in the study. The backsides of barrier islands face These data were then combined with an Overview estuarine wave conditions, but with less analysis of various sets of old aerial energy than the ocean side. Everts et al. photographs obtained from the U.S. The Albemarle Sound, the northern- (1983) reviewed shoreline change Department of Agriculture, Soil Conser- most component of the North Carolina between 1852 and 1980 for the region vation Service offices in each coastal estuarine system, features a vast, fresh to from Cape Henry to just west of Cape county studied. The results were subse- low-brackish water complex of creeks, Hatteras. They concluded that the back- quently integrated with the USDA-SCS rivers, and open-water sounds (Table 3.4, barrier estuarine shorelines were generally (1975) study of estuarine shoreline page 41). Two trunk rivers, the Chowan in an erosional state. The average retreat erosion in the N.C. coastal counties. and the Roanoke, combine to form the rate for the north-south oriented shorelines Tables 2.2 and 2.3 (pages 24 and 25) Albemarle Sound. Flowing into the was 0.33 ft/yr or 33 ft/100 yrs., in contrast summarize the distribution and total Albemarle Sound, from west to east, are to the ocean shoreline, which had an abundance of shoreline types and the the following drowned tributary estuaries: average retreat rate of 2.6 ft/yr. The east- natural and human features that modify Yeopim, Perquimans, Little, Pasquotank west oriented back-barrier estuarine various shoreline types, respectively, in and North rivers on the north side of shorelines (W of Cape Hatteras) eroded at northeastern North Carolina. Table 2.1 Albemarle Sound, and the Scuppernong an average rate of 4 ft/yr between about (page 24) summarizes the average rate of and Alligator rivers on the south side. At 1850 to 1980, for an average total estuarine shoreline erosion for shoreline the eastern end of Albemarle Sound are recession of 530 ft. in 130 years. The types within northeastern North Carolina. three moderately large and open back- Everts et al. report also concluded that the The following publications resulted from barrier estuarine bodies, including back-barrier estuarine shorelines from these studies: Bellis, O’Connor, and Currituck, Croatan and Roanoke sounds. Cape Henry to Cape Hatteras increased Riggs (1975); O’Connor, Riggs, and The total shoreline within the system their net retreat rate between 1850 and Bellis (1978); Riggs, O’Connor, and exceeds 500 miles and touches nine 1980, reaching their maximum in the Bellis (1978); Hartness and Pearson counties: Bertie, Camden, Chowan, 1949-1980 period, while the Buxton (1977); and Hardaway (1980). Currituck, Dare, Pasquotank, Perquimans, Woods estuarine shoreline west of Cape Centerfold maps for the Albemarle Tyrrell and Washington. Hatteras displayed the opposite trend. Sound, Pamlico River, Neuse River and Figure 3.3 (centerfold) summarizes Core-Bogue sounds will summarize the the distribution of shoreline types for the Albemarle-Pamlico Estuarine distribution of shoreline types for the Albemarle estuarine system. Sediment System areas studies. The maps indicate coastal banks comprise roughly half of the shore- segments that were experiencing lines in the system, with the remaining half Riggs and his colleagues at East significant erosion and portions that were evenly divided between swampforest and Carolina University carried out numerous modified and protected by some form of marsh. Erosion is ubiquitous and can be studies during the 1970s on estuarine hardened structure at the time of field locally severe with many areas showing shoreline erosion in the N.C. coastal mapping in 1975-1976. Each shoreline recession far in excess of the average for system. These initial studies were done segment is mapped as a specific shoreline North Carolina estuaries. This erosion is Page 31 T h e S o u n d f r o n t S e r i e s FIGURE 3.2. Map shows the location of estuarine shoreline erosion studies in the North Carolina coastal system by Riggs and his colleagues at East Carolina University. Page 32 S h o r e l i n e E r o s i o n due primarily to the general orientation of Low-Bank Shorelines. PAMLICO RIVER AND Albemarle Sound, coupled with large fetches Low-bank shorelines are the most PAMLICO SOUND that are commonly more than 50 miles. abundant type and are dominant within ESTUARINE SYSTEM Tyrrell, Pasquotank and Camden Shoreline Descriptions counties. Erosion of low-bank shorelines Overview is typically very severe. In most areas, Table 3.4 (page 41) summarizes the the sediments are unconsolidated and The Pamlico River estuarine system general distribution and abundance of the virtually melt when wind tides raise the is the flooded portion of the Tar River and five dominant shoreline types by county erosive action of waves up and over the associated tributary streams.