Dune belt restoration effectiveness assessed by UAV topographic surveys (Northern Adriatic coast, Italy)

Abstract

Abstract. Unmanned Aerial Vehicle (UAV) monitoring surveys are used to assess a dune restoration project in the protected natural area of the Bevano River mouth in the Northern Adriatic coast (Ravenna, Italy). UAV is among the most utilized tools in coastal geomorphology studies as high-spatial and temporal resolution surveys can be carried out in an efficient and cost-effective manner. The impact of the installed fences to dune development are assessed in terms of sand volume and vegetation cover changes over time by using a systematic data processing workflow based on Structure from Motion (SfM) photogrammetry and Geomorphic Change Detection (GCD) toolset. Accuracy assessment is performed using statistical analysis between GPS profiles and the elevation models. Results show that the dune fence proves to be effective to prevent dune erosion since significant sand accumulation is observed along the dune foot and front. Progradation of around 3–5 m of the foredune, development of embryo dunes, decrease in stoss slope and blowout features due to increase in vegetation colonization were observed. Erosion is evident at the northern portion of the structure, which could be accounted for by the aerodynamic and morphodynamic conditions around the dune fence, the efficiency of the fence and its configuration to trap sediments. Dune fencing and limiting debris cleaning along the protected coast has been proven to be very effective against dune degradation. The GCD toolset can be a valuable tool if sources of uncertainties are well accounted for. The proposed workflow can also aid in creating transferable guidelines to stakeholders in ICZM implementation in the Mediterranean low-lying sandy coasts.