MONITORING COASTAL GEOMORPHOLOGY THROUGH VOLUMETRIC QUANTIFICATIONS OF TOPOGRAPHICAL CHANGE: ESTABLISHMENT OF A REGIONAL PROTOCOL

Considering the connection of increasing rates of sea-level rise and intensifying storm-impact regimes to destructive topographical changes at the coast, and the significant 20^th century development along the mid-Atlantic and northeastern US coastline, the regional threat to infrastructure and natural resources has never been greater. Locally, natural and constructed interruptions to sediment transport pathways create fixed areas of rapid erosion that are particularly vulnerable. As a result, there is significant spatial inequity in the impacts affecting localized areas within the broader background framework of a globally rising sea level and low regional sediment supply that creates a need for site specific coastal geomorphological monitoring.

Through the Northeast Coastal and Barrier Network of the National Park Service, we have developed and implemented a protocol, “Coastal Landform Elevation Models”, for the collection of high accuracy topographical data to volumetrically measure coastal geomorphological change. The protocol is a component of a regionally applied geomorphological monitoring program, complementing the previously established Shoreline Position (1D) and Coastal Topography (2D) protocols. The data is collected according to standardized procedures defined in the protocol to facilitate the volumetric quantification of topographical change and measurement of landform displacements for areas comprising relatively small lengths of shoreline (1-2 km) that are experiencing rapid erosion. The procedures described in the protocol emphasize 1) the consistent and accurate collection of 3D topographical data with highly accurate (2-4 cm) GPS survey equipment, 2) the appropriate management and processing of the collected data to enable the calculation of volumetric change, and 3) robust analyses to derive spatial trends and patterns of geomorphological change at a variety of temporal scales ranging from storm impacts to long term trends. The outputs deliver the rates of sediment loss, directly identifying the deficit of material within the local system, and spatial patterns of erosion and deposition that characterize the pathways for sediment transport. Considered together, predictions can be made regarding the exposure of resources to coastal geomorphological change.