Monitoring Stream Bank Erosion Under Different Riparian Land Uses Utilizing Various Methodological Approaches

Stream bank erosion is a major pathway by which sediment reaches and pollutes water bodies. Nature-based solutions, such as riparian forests, can help significantly reduce stream bank erosion rates. There have been major research efforts in this scientific field worldwide, but there is a finite number of such studies in Greece. The objective of this study was to estimate erosion rates of a typical Greek watershed with different riparian land uses. The specific watershed studied was Aggitis, which is located in Northern Greece. Erosion rates were estimated using traditional methods (e.g., erosion pins) and new methods (laser scanning and unmanned air vehicles). The different riparian land uses studied were: 1) Agricultural lands, 2) Broad-leaved forests, 3) Natural grasslands and, 4) Sclerophyllous vegetation. Forty erosion pin plots, equally distributed among the land uses, were established and measured. Each plot had ten pins. Three stream reaches to be monitored by laser scanning and the unmanned air vehicles were selected that had different geomorphological characteristics. The laser scanner collects high-resolution data on stream banks. Unmanned aerial vehicles can capture images of the reach and afterward create the necessary orthophotos to detect changes. Overall, the sclerophyllous vegetation and broadleaved forests had the lowest rates. When comparing the three methods, laser scanning provides very high accuracy measurements. At the same time the images from unmanned air vehicles allow us to also detect, with high accuracy, eroding bank sites but at a greater scale.