UAVs multispectral camera detection of seasonal changes in a restored salt marsh.

Salt marsh evolution is strongly affected by tidal processes and ecology which regulate sediment accretion and erosional rates. A balance between erosion and deposition in a restored salt marsh is crucial for analyzing restoration strategies to adopt in a natural context. Here, we present an integrated approach monitoring salt marsh seasonal changes over several months in a low energy restored salt marsh of the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island (Maryland, USA). The project is a restoration site where sediment dredged from the shipping channels in the upper Chesapeake Bay is being used to restore a tidal marsh habitat in mid-Chesapeake Bay. We flew an Unmanned Aerial Vehicle (UAV) with an RGB camera to obtain a high-resolution map of the planimetric position of vegetation and a multispectral camera to monitor the healthiness of the marsh community along seasons. Due to its extension of 400 m by 400 m, a total of four flight plans were necessary to cover the entire cell flying at a 40 m altitude, in order to obtain a 2 cm Ground Sample Distance (GSD). This technique provides reliable results at a very low cost, allowing an accurate assessment of the marsh platforms over time, thanks to both the very high spatial resolution and the precise georeferencing of the images for the comparisons. Detecting salt marsh evolution and seasonality coupled with field measurements can help to improve the accuracy of eco-geomorphic models. Understanding the drivers of salt marsh evolution is vital for informing restoration practices and designs to improve resilience and coastal management strategies.