CRHyME (Climatic Rainfall Hydrogeological Model Experiment): a new model for geo-hydrological hazard assessment at the basin scale

Abstract. This work presents the new model called CRHyME (Climatic Rainfall Hydrogeological Modelling Experiment), a tool for the geo-hydrological hazard evaluation. CRHyME is a physically based and spatially distributed model written in Python language and represents an extension of the classic hydrological models that simulate inflows-outflows at the basin scale. A series of routines have been integrated to describe the phenomena of geo-hydrological instabilities such as the 10 triggering of shallow landslides as well as debris flows, catchment erosion, and sediment transport into the river. These phenomena are generally decoupled with respect to the continuous hydrological simulation while in CRHyME they are quantitatively and simultaneously evaluated through a multi-hazard approach.

CRHyME has been tested on some case studies located in Italian basins. Valtellina and Emilia's areas were considered for the calibration and validation procedures of the model thanks also to the availability of literature data concerning past occurred 15 geo-hydrological instability phenomena. Calibration and validation of the model conducted on presented case studies have been assessed through some hydrological indexes such as NSE (Nash–Sutcliffe Efficiency) and RMSE (Root Mean Square Error) while for landslide phenomena the ROC (Receiver Operating Characteristic) methodology was applied. CHRyME has been able to: 1) reconstruct the surface runoff at the reference hydrometric stations located at the outlets of the basins, 2) estimate the solid transport at some hydropower reservoirs compared to the reference data, and 3) evaluate the triggering of 20 shallow landslides and debris flows compared to those recorded in the literature. The ranking has shown a rather good performance of the model in terms of numerical conservativity of water and solid balances, revealing suitable not only for back-analysis studies but also as an efficient tool for Civil Protection multi-hazard assessment.