Bottom topography constitutes an important basis for analysis of how hydropower or other factors affect physical conditions and life in rivers. Extensive collection of data on river topography is often time- and resource-consuming. The researchers have therefore sought to find ways for efficient mapping of the riverbed and associated parameters in time and space using remote sensing sources.

Example of a riverbed map in the river Nea, Trøndelag. Green outline indicates river corridor with water flow from right to left. The map has been created by combining green LIDAR, satellite images and aerial photography. Illustration from own publication.

Can map waterways faster and cheaper

With the help of multispectral images from satellites, aircrafts, or drones, preferably in combination with LIDAR and local measurements, it is possible to map bottom topography in large parts of watercourses. When accessing new and updated images, the method(s) can be repeated and used to monitor changes over time.

The methods enable extended environmental design in the form of extensive watercourse modelling and monitoring. With the help of the developed methods, researchers, consultants, and power companies can create riverbed maps at different water courses, provided that the image quality is satisfactory and local conditions are sufficient for the use of the methods. The riverbed maps can potentially be used in analysis of physical measures linked to, for example, habitats for local key species or minimum water discharge in rivers.

Another relevant use is updating flood zone maps and analysis of the area covered by water on various watercourses.

Principle sketch for various remote sensing technologies. Blue line indicates water surface, while green line is the topography of the landscape. The sketch shows which parts of the landscape are mapped by the various technologies. Satellites (top left) record water levels and larger parts of the landscape beyond the river. Green LIDAR (top right) records the riverbed (and surface) in addition to smaller parts of the landscape outside the river. Drones (bottom left) record water levels and smaller parts of the landscape beyond the river. Sonar / sonar (bottom right) records the riverbed and can also measure water speeds.