Where land meets sea: towards a complete coverage for terrain analysis of coastal environments

Developments in remote sensing techniques to produce digital terrain models (DTM) have provided new methods for studying terrestrial environments, thereby improving scientific understanding of ecological and geomorphological processes. Geomorphometry, or terrain analysis, uses DTMs to quantify physical characteristics of the land (e.g., slope or rugosity) that are used for different applications such as habitat mapping. The use of multibeam echosounder systems (MBES) to measure seafloor relief has changed the way we study and understand marine environments; techniques from geomorphometry are now commonly applied to these underwater DTMs for the investigation of marine habitats and geomorphology. Due to the inability of satellite remote sensing to collect data in deep waters and the limitations of MBES data collection in shallower waters, there is often a gap in terrain data where land meets sea. A seamless analysis of terrestrial and marine environments requires the combination of terrestrial DTMs, bathymetric data from MBES, and bathymetric LiDAR to fill this gap. The challenges encountered with merging datasets from different sources, such as data uncertainty or spatial resolution, makes such an approach still nascent in the literature. Using data from coastal Newfoundland and Labrador, this contribution reviews the potential uses of continuous terrestrial/marine terrain models, especially for the field of geomorphometry and its application in coastal environments. We argue that such DTMs can become essential to applications like coastal habitat mapping, identification of hazards for navigation in shallow waters, or studying landforms that overlap between environments. We also discuss how some techniques traditionally used in terrestrial studies, such as Geographic object-based image analysis (Geobia), can be applied in marine studies.