UAVs to assess channels' shape evolution in a restored salt marsh

Salt marsh evolution is strongly affected by tidal processes that regulate sediment accretion rates and vegetated platform erosion. 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 channels morphodynamic over a few years' time frame in a low energy 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. Starting from the cross section of every channel measured in the initial project GNSS survey, then, a detection has been performed using both a traditional GNSS Real Time Kinematic for the accurate cross sections survey and an Unmanned Aerial Vehicle (UAV) to high resolution map the planimetric position of the channels and the vegetation's platform. Due to its extent of 400m by 400m, a total of three flight plans was necessary to cover the entire cell flying at a 40m altitude, in order to obtain a 2cm Ground Sample Distance (GSD). This technique provides reliable results at a very low cost, allowing an accurate assessment of the channels dynamics over time, thanks to both the very high spatial resolution and the precise georeferencing of the images for the comparisons. Detecting tidal channels morphodynamic coupled with suspended sediment concentration recorded through Aqua Doppler Current Profilers (ADCPs) deployment and suspended sediment samples can help to improve accuracy of numerical models. Understanding the drivers of salt marsh evolution is vital for informing restoration practices and designs to improve resilience and coastal management strategies.