A 2100-YEAR RECORD OF COASTAL SYSTEM CHANGES IN RESPONSE TO SHIFTS IN RATES OF RELATIVE SEA-LEVEL RISE

The relative sea-level rise (RSLR) record for NE North Carolina’s (NC) coastal system is based on rates of salt-marsh vertical accumulation, a proxy for RSLR. Over the past 2100 years the record of RSLR in NC documents two intervals of slow (S1 and S2) and two intervals of more rapid (R1 and R2) rise rates.

TIME INTERVALS*	RELATIVE SLR	AVE. RATE RSLR
S1 100 BC— 950 AD = 1050 yrs	1050 mm	1.0 mm/yr
R1 950 AD—1350 AD = 400 yrs	640 mm	1.6 mm/yr
S2 1350 AD—1880 AD = 530 yrs	477 mm	0.9 mm/yr
R2 1880 AD—2000 AD = 120 yrs	372 mm	3.1 mm/yr

*Based upon inflection points on the Kemp et al. NC RSL curve

These intervals correlate with documented geomorphic and ecosystem changes within the NC coastal system. Geologic data indicate that slow RSLR rates correlate to periods of maximum barrier island development with few inlets and low brackish to fresh back-barrier estuaries. Intervals of more rapid RSLR rates correlate to periods of minimum barrier island development with extensive inlet-shoal systems and high brackish estuaries with increased tidal range. Changes in rates of RSLR had a significant impact upon European settlement and subsequent history of NC’s coastal plain. From 1584 to late 1800s the barrier islands were dominated by shoreline accretion with decreasing number of inlet-shoal systems. Since the late 1800s the barriers have been dominated by island narrowing with increasing number of inlets in spite of extensive human efforts to prevent and minimize their existence. Additionally, the transition from a slow (S2) to the current more rapid rate of RSLR (R2), resulted in the following coastal system responses. 1) Croatan Creek, a drowned-river tributary estuary, flooded across an inter-stream divide to produce the shore-parallel Croatan Sound; 2) estuarine shorelines experienced substantial erosion resulting in a significant loss of land and wetland habitat; and 3) numerous human features built in the 17^th to 19^th centuries such as wharfs and other lowland structures, drowned beneath the rising sea. If the current rate of RSLR continues to increase, major segments of the barrier islands will likely collapse into broad inlet-shoal systems and the fresh to low-brackish water, wind-tide dominated Pamlico, Croatan, Albemarle, and Currituck sounds will evolve into salt-water estuaries dominated by astronomical tides.