A Short History of a Flat Place: Three Centuries of Geomorphic Change in the Croatan National Forest

Abstract

Despite flat terrain, extensive forests, and little urbanization, there has been extensive landscape change in the Croatan area of North Carolina's lower coastal plain in the past 300 years. Culturally-accelerated erosion, sedimentation, and geomorphic change are documented, including mean historic upland surface lowering of 15 to 25 cm, and historic alluvial sedimentation of 70 to more than 200 cm. This recent environmental history is significant beyond the Croatan because it illustrates three critical points. First, human agency can result in rapid and significant geomorphic change, even in geologically stable areas where traditional geomorphic risk factors such as slope and climate variability are low. Second, geomorphic change may not leave obvious visible clues. The scarcity of apparent landform change in the coastal plain has traditionally left the impression that culturally-induced geomorphic change has been minimal, when in fact such changes are comparable to those in other regions generally recognized as having undergone serious land degradation. Third, the impacts of human agency on geomorphic processes can be difficult to recognize when those impacts are intertwined with other geomorphic changes. In the Croatan, some human impacts are similar to those associated with Holocene sea level rise, though greatly accelerated. This makes historic change difficult to distinguish from longer-term Quaternary environmental changes.

Soil redistribution and pedologic transformations in coastal plain croplands

“…In this sense, about half the study area (the 35 cultivated hectares) has undergone a transition. The truncation estimate is based on the cemetery data, but is less than the general DTA differences between the forested and cultivated areas, and is consistent with previous studies of profile truncation in the southeastern coastal plain (Cooper et al, 1987;Lowrance et al, 1988;Phillips, 1993Phillips, , 1997Phillips et al, 1993). Our guess is that about 20 per cent of the cultivated area has experienced truncation or accretion sufficient to result in taxonomic reclassification, independently of or in addition to the general transition from the thicker forested to the thinner cultivated soils.…”

“…It has been increasingly recognized in recent years that despite low slopes, a prevalence of sandy permeable soils, dense natural vegetation, and the relative scarcity of visible erosion indicators, the southeastern coastal plain has undergone historic soil erosion at rates of significance both to geomorphology and environmental management (Dendy, 1981;Cooper et al, 1987;Soller, 1988;Lowrance et al, 1988;Phillips et al, 1993;Phillips, 1997;Slattery et al, 1997). Much of the soil loss is clearly due to fluvial processes, as evidence of recent and historical sedimentation linked to upland erosion abounds.…”

“…Measurements or estimates of erosion rates on cropland typically range from 5 to more than 30t ha ±1 a ±1 (Beasley, 1979;Dendy, 1981;Sheridan et al, 1982;Lowrance et al, 1986Lowrance et al, , 1988Cooper et al, 1987;Phillips, 1993Phillips, , 1997Phillips et al, 1993;Slattery et al, 1997), while sediment yields of coastal plain streams are, at least an order of magnitude lower (Dole and Stabler, 1909;Kennedy, 1964;USDA, 1979;Simmons, 1988;Hubbard et al, 1990;Kim, 1990). The disparity between sediment eroded from hillslopes and fluvial sediment yields is well known and occurs in a variey of environments, but is often particularly evident in the coastal plain.…”

Historical Legacies, Information and Contemporary Water Science and Management

“…Certainly, in cases where low-head dams played a role in sediment storage [28,29], this incision begins with the breaching of dams whether during the malaria scares in the mid 1800s [30] or in the recent push to re-establish free flowing hydrologic systems [31,32]. However, the accumulation of floodplain sediment occurred throughout the Piedmont, even in areas without extraordinary dam density [33].…”

Mining Impacts on the Fresh Water Environment: Technical and Managerial Guidelines for Catchment Scale Management

“…While bed sediment can be viewed as a "sink" for pollutants, it can also function as an important contributor of remobilised contaminants to the environment, in many cases long after the original discharges have ended (Miles and Harris 1971). Furthermore, metals immobilised in aquatic sediments and floodplain soils may contribute substantially to downstream metal concentrations (Martin 1997(Martin , 2000: a large percentage of eroded sediments are often stored in the drainage basin rather than removed immediately from it and, over time (years to centuries), they move through the basin during flood episodes (James 1989;Beach 1994;Philips 1997). Benthic organisms living in metals-contaminated sediments have two primary routes of exposure: direct exposure to metals in (surface and pore) water and the accumulation of metals via food supply (as particulate matter in the tissue of other organisms).…”