Monitoring Bluff Erosion on the Boston Harbor with Terrestrial Laser Scanning
Samuel Soule, Geology and Geophysics
Project Funded 2009:
Bluffs composed of weakly lithified sediments are common along coastlines globally and are subject to rapid and episodic retreat. Their retreat has significant impact on densely populated coastalcommunities and this impact is expected to become more significant with predicted sealevel rise in the coming decades. Heavily populated shorelines of this type might consider such retreat a threat; however, the redistribution of sediment from bluffs is also requisite for maintaining healthy beaches and proximal marsh ecosystems threatened by sea-level rise. This is one example of the complexity of issues presented by coastal change, issues that are best addressed with the most accurate assessments of the rates of change and the mechanisms controlling them. This project will apply a novel technology, ground-based LiDAR (Light Detection and Ranging), to gain a new perspective on bluff retreat processes in the Boston Harbor Islands. LiDAR uses a near-infrared laser to collect millions of range measurements across a target in order to produce a high-resolution three-dimensional map of the ground surface. Monthly LiDAR scans will be collected on bluffs composed of weakly to unconsolidated glacial material throughout the winter (Nov. to April) when wave energy and storminess are at their greatest. These data will be used to quantify rates of bluff retreat at higher spatial resolution than traditional bluff-face profiles and to measure the morphologic characteristics of the bluff face that indicate the mechanisms of retreat. In addition, gridded 3D data of bluff faces will be differenced to accurately quantify the spatial extent and volume of sediment loss with time. The improved spatial and temporal resolution of LiDAR over traditional methods of measuring bluff retreat will provide the necessary information to accurately link mechanisms and rates of sediment removal from the bluffs to causal events and environmental conditions.