A clustering classification of catchment anthropogenic modification and relationships with floods

Anthropogenic modifications at catchments scale may be reconducted primarily at soil sealing and streams culverting, even if important consequences result from roads density and, more in general, infrastructures as they cause landscape fragmentation, and agricultural areas extension. Their most important outcomes in terms of hydrologic balance are the decreasing time of concentration and the increasing flood risk at catchment scale. The research introduces a methodological approach to classify the degree of anthropogenic modifications at catchment scale: clustering techniques have been applied to 508 catchments in a high-risk flooding sector of the Mediterranean region. Then, flood data recorded in the study area in the 1900-2018 period have been compared to clustering classification, pointing out the relationships with soil sealing and hydrographical network culverting in the catchment. The analysis has been performed considering fourteen subsets of 8 descriptive parameters each that differ in the evaluation of culverting in the terminal part of the hydrographical network; the analysis has been conducted identifying the optimal number of descriptive parameters and the corresponding best number of clusters on quantitative basis. The results show that three classes clustering is the more appropriate from a computational point of view. That division looks coherent with the features of the studied basins and is well correlated with floods occurrence in the last 100 years. Finally, the proposed methodology of anthropogenic disturbance classification at catchment scale may be applied to other areas even adapting and implementing other descriptive parameters. Then, it may be used to support the planning of mitigation strategies in term of flood risk.