Identification and geomorphic characterization of fluvial knickzones in bedrock rivers from Courel Mountains Geopark

Abstract

The gradient characteristics of Courel Mountains Geopark bedrock rivers were examined. Unlike alluvial rivers, bedrock rivers have been the great forgotten of fluvial geomorphology globally. Based on the decreasing rate of gradient with increasing measurement length, a relative steepness was obtained as indicator of knickzone. Supported by GIS techniques and DEMs, the changes in slope along the longitudinal profile of the rivers were detected. The number of the extracted knickzones rises to 325, which means a frequency of knickzones of 0.467 km−1. The total length of the knickzones is 285 km, representing about half of the drainage network as knickzone (47%). The mean height, the length, and the gradient of all the knickzones were ~ 110 m, ~ 880 m, and 0.178 m·m−1, respectively. There is no distribution pattern and the knickzones are everywhere, although they are more present in reaches with NW–SE direction and order 1. Several environmental factors were crossed to know more about the occurrence and knickzones characteristics, suggesting that density and direction of fractures regulate the number and the trajectory of the knickzones, while the lithology controls the singularity of the forms. The geomorphological and the topographical characteristics of the bedrock rivers make them high ecological, scenic, landscape, and recreational value. Findings from this study can be also used by managers to develop and/or improve strategies for conservation, valorisation, and how to approach the tourist who visits the Geopark. Scientific tourism can offer a unique and educational travel experience, allowing participants to learn about bedrock rivers and knickzones.