Abstract
High costs and project-based (short-term) financing mean that coastal engineering projects are
often undertaken in the absence of appropriate post-construction monitoring programmes.
Consequently, the performance of shoreline-stabilizing structures or beach nourishments cannot be
properly quantified. Given the high value of beaches and the increase in erosion problems and coastal
engineering responses, managers require as much accurate data as possible to support efficient
decision-making. This work presents a methodological approach to characterise coastline position
changes as a result of engineering actions. We describe a new, low-cost method based on satellite
remote sensing to monitor shoreline evolution at high temporal and spatial resolution pre-, during
and post-implementation. Initially, satellite-derived waterlines are identified and extracted from
publicly available satellite imagery of the Landsat 5, 7, 8, and 9, and Sentinel-2 constellations using the
automatic shoreline extraction tool SHOREX. The waterline positions are then compiled, differences
over time are quantified, and a matrix is constructed that allows easy depiction and interpretation
of spatial and temporal patterns of erosion/accretion. This allows the access and the comprehension
of the morphological data by the non-expert. Two examples of application on the Valencian coast
of Spain at different spatial scales demonstrate how beach response to coastal engineering actions
can be characterised at different levels of detail (from local to regional) and over different periods of
time. These applications evidence the utility of the approach as it allows analysis of pre- and postintervention coastal change and offers a means to overcome the widespread lack of monitoring and
hence to improve coastal engineering practice.
