On the use of satellite-based Digital Elevation Models to determine coastal topography

Abstract

Around 600 million people worldwide live in coastal areas being exposed to coastal flooding. Global coastal flooding risk can be determined by the chance of surpassing a certain elevation (e.g. maximum height of the dunes) by the total sea level at the coast (depending on the beach slope). Considering this, beach slopes and local maximum elevation, hence topographies, are required on a global scale to assess globally changing flood risk exposure. Several satellite-derived Digital Elevation Models (DEMs) exist that cover most of the world and can provide these required data. In this study we explore the use of these DEMs (NASA’ SRTM, JAXA’ ALOS and Airbus’ WorldDEM) in terms of beach slope, dune top elevation in comparison to airborne-LiDAR derived values. The results show the ability to extract coastal features, in particular at the upper beach face. The DEMs perform better in case of steep beaches with slopes between 0.1 - 0.15 The ability to extract beach slope accurately seems not to depend on the DEM’ accuracy nor resolution but mainly a function of the reconstruction and/or sensing method. Coastal zones, often large area, require fine resolution for flood risks assessments. Very-high resolution satellites such as the Pleiades constellation can provide the required kind of detail (DEMs 2m x 2m).