Can we characterize river corridor evolution at a continental scale from historical topographic maps? A first assessment from the comparison of four countries

Abstract

National historical map resources are assessed in four European countries to charac-terize river corridor features and associated channel changes, as well as identifyissues limiting or promoting geomorphic assessment procedures at a continentalscale. A geomorphic audit that launches potential data for diagnosis from reach tocontinental scales could offer a good resource for biology and ecology managers ofriver authorities or government agencies and engineers. The assessment comparesthe resources available by country in terms of period covered, spatial scale, historyand chronology, and representation of the fluvial corridor features. We then appliedthe Historical Maps Vectorization Toolbox, initially developed for vectorizing rivercorridors from French maps, to detect and extract flow channels, unvegetated barsand riparian vegetation patches from historical topographical maps. We found that(a) it is difficult to apply an audit of channel changes to the whole continental scalebecause map legends differ between countries due to geographic and political speci-ficity; (b) there exists an opportunity to get assessment information in all countries atreach or national scale where map resources are available; (c) the highest potential isobserved in Switzerland and Belgium where there is high quality national map cover-age from the 19th century; and (d) the algorithm Historical Maps Vectorization Tool-box applied to map resources works well with any of the countries, and itswidespread application is encouraging.