Use of Unoccupied Aerial Vehicle (Drones) Based Remote Sensing to Model Platform Topography and Identify Human-made Earthen Barriers in Salt Marshes

Elevation is a foundational driver of salt marsh morphology. Elevation governs inundation and hydrological patterns, vegetation distribution, and soil health. Anthropogenic impacts at grand scales (e.g., rising sea levels) and local scales (e.g., infrastructure) have altered the elevation of the salt marsh surface, changing the topography and morphology of these ecosystems. This study establishes and assesses means to document and analyze these impacts using Unoccupied Aerial Vehicle (UAV) based remote sensing to model platform topography. This thesis’s first and primary study presents and compares methods of producing high-resolution digital terrain models (DTMs) with UAV-based Digital Aerial Photogrammetry (DAP) and Light Detection and Ranging (LiDAR) in conjunction with various filtering techniques. Fifty-one models were produced to analyze three 0.19 to 0.42 km2 salt marsh sites on the coast of Massachusetts. Compared to DAP, filtered LiDAR provided the highest accuracy across all sites. The second study presents a case study demonstrating the utility of high-resolution terrain models. Using the models produced of the Red River salt marsh in Harwich/Chatham, MA, human-made earthen barriers (embankments) were mapped and their impacts evaluated. Historically constructed for agriculture and transportation, embankments have greatly altered the topography and, likewise, ecology of Massachusetts salt marshes. In documenting and quantifying the impacts of these structures, this case study demonstrates the utility of incorporating UAV-based remote sensing topographical analyses in salt marsh site assessments.