Hydromorphological Information in Historical Maps of Switzerland: From Map Feature Definition to Ecological Metric Derivation

This article focuses on defining hydromorphological features to be extracted from historical maps by means of digital map processing techniques. The hydromorphological features, evolving through time, can be described quantitatively by the development and application of various ecological metrics to study the spatiotemporal change of the natural and built freshwater environment. With the goal to support future revitalization efforts, this article first reviews the theory on quantifying spatiotemporal change using landscape and ecological metrics, ranging from simple shape metrics (e.g., shoreline length) to more complex hydromorphological indexes (e.g., river braiding index). Second, the hydromorphological features themselves are important to consider in terms of data quality and uncertainty as they might inherit errors due to the low-quality maps, the extraction process, or due to poor definitions used during feature extraction efforts. Errors introduced by poorly defined features can be avoided by the use of a well-structured definition system. Thus, the article concludes in a new concept categorizing hydromorphological features and the changes they can undergo. The definition framework integrates novel perspectives for defining and evaluating features from the Siegfried and old Swiss national map, including key aspects from the theory.