GEOMORPHIC ELEMENTS AND SURFACE WATER FLOW PATHS INTERPRETED FROM A LIDAR-BASED LANDFORM ANALYSIS OF A QUATERNARY COASTAL PLAIN LANDSCAPE IN NORTH CAROLINA

The purpose of this talk is threefold: 1) to summarize the geomorphic elements interpreted from LiDAR that are preserved on a Quaternary Coastal Plain landscape; 2) to identify the upstream landforms associated with the active Holocene depositional system (which dissects this landscape); and 3) to demonstrate that detailed mapping of these landforms permits the interpretation of surface water flowpaths from field to stream. The study area includes parts of four 7.5 minute quadrangles (Farmville, Walstonburg, Fountain and Falkland). Elevations range from ~14 to 38 m. North to northeast trending segments of the early Pleistocene Surry paleoshoreline (old toe 29-30 m) extend through this area. A barrier island complex occurs locally along the paleoshoreline. East of the Surry shoreline are a series of younger (albeit Early Pleistocene) probable offlapping units. Landward of the barrier are additional Early Pleistocene landscape features. The Early Pleistocene ramps are situated on the interfluve that separates the Neuse and Tar-Pamlico paleo-incised valleys. Ramps are dissected by streams in drainages that form small-scale incised valleys that merge downstream with the basin-scale incised valleys. Small-scale incised valleys are floored with a mappable wetland flat. Fringing the wetland flat are side colluvium and relict riverine terraces that are flooded during high water stages. Upstream, the wetland flat abruptly ends and is replaced by colluvium with an incised channel that transports water and sediment from upland terraces to the wetland flat. The incised channel at the head of the alluvial valley may lead upstream to a circular concave depression that serves as a gathering basin for surface water. These valley-head basins may have steep, scarped walls, resembling sinkholes, or Carolina Bays, or a combination of the two. Surface water from storms gathers in basins at the heads of drainages, and is funneled downstream through incised channels which may feed alluvial fans that build downstream over the wetland flats. The overall surface of the wetland flat dips gently downstream; but the landform unit may consist of a series of wetland flats that step down along low-elevation scarps transected by a short incised channel that connects adjacent wetlands.