Assessing the utility of high-spatial-resolution remote sensing to monitor shoreline change in three coastal National Park units

Cooper, Halle; Fichot, Cédric G.

In this pilot study for the National Park Service (NPS), we assessed the feasibility of using two commercial remote sensing satellite programs, Planetscope and Maxar, to reliably document and monitor shoreline change. This study is in response to NPS’s growing interest in using remote sensing to better track shoreline change across their 88 coastal National Park units. While field efforts of shoreline monitoring are typically limited to a few key locations, remote sensing provides an unparalleled level of spatial and temporal information. Planetscope and Maxar have significantly more frequent (Planetscope) and fine-resolution (Maxar) imagery than other satellite programs, giving them potential to facilitate expansive and accurate shoreline monitoring and detect change on small spatial scales (a few meters). In this pilot study, we analyzed shoreline change in three contrasting coastal National Park units from 2016 to 2021 using two methodologies. By comparing the outputs obtained from the Planetscope and Maxar satellite imagery, we were able to identify how each dataset can provide information about shoreline change. Our results demonstrate the difficulty of mapping small-scale shoreline change amidst water level variation caused by tides, net precipitation, and seasons, and the importance of Planetscope’s frequent acquisition in overcoming this difficulty. While the finer spatial resolution of Maxar is appealing (30-60 cm vs ~3-5 m for Planetscope), its value is limited for shorelines and areas that experience frequent water level variation (e.g. from tides) due to sporadic data collection. However, Maxar’s fine spatial resolution may aid in the analysis of bluffs or lakeshores that do not experience significant water level variation. Overall, the two satellite programs have the potential to complement each other. Combining Planetscope imagery that allows for automated high-level analysis and the fine resolution of Maxar imagery for further exploration of bluff or other non-inundated areas creates a two-step workflow that can provide accurate and detailed shoreline analysis. While we found that varying levels of remote sensing difficulties arise depending on geographic location and tidal influence, the study was successful in detecting areas of rapid shoreline change that may need careful monitoring and management. Adoption of this remote sensing workflow could greatly influence shoreline monitoring and facilitate management decisions for the entire suite of coastal National Park units.