Structure-from-Motion (SfM) monitoring of nourished gravel beaches in Croatia

Beach nourishment is now widely used as a “soft” coastal protection but its performance is still relatively poorly understood. Beach monitoring allows performance analysis over a range of environmental conditions which, in turn, can provide the basis for successful nourishment design and implementation. Remote sensing techniques based on Structure-from-Motion (SfM) have been successfully used in geomorphological studies in a range of environments, including gravel beaches (James et al., 2013). This paper presents applications of SfM to two nourished beaches in Croatia.

The two different beaches were monitored using different “remote sensing platforms”. First, a larger natural gravel embayed beach was surveyed by unmanned aerial vehicle (UAV). Secondly, an artificial gravel pocket beach was surveyed by using a pole-mounted hand-held camera from the ground. These two cases demonstrated that the SfM method has many advantages in comparison with traditional methods by providing high-resolution 3D data, and being easy to implement and affordable. Hence it has a great potential for regular beach surveys in Croatia to deliver the process understanding required to inform implementations of nourishment schemes.