Analysis of Climate Change’s Effect on Flood Risk. Case Study of Reinosa in the Ebro River Basin

Abstract

Floods are one of the natural hazards that could be most affected by climate change, causing great economic damage and casualties in the world. On December 2019 in Reinosa (Cantabria, Spain), took place one of the worst floods in memory. Implementation of DIRECTIVE 2007/60/EC for the assessment and management of flood risks in Spain enabled the detection of this river basin with a potential significant flood risk via a preliminary flood risk assessment, and flood hazard and flood risk maps were developed. The main objective of this paper is to present a methodology to estimate climate change’s effects on flood hazard and flood risk, with Reinosa as the case study. This river basin is affected by the snow phenomenon, even more sensitive to climate change. Using different climate models, regarding a scenario of comparatively high greenhouse gas emissions (RCP8.5), with daily temperature and precipitation data from years 2007–2070, and comparing results in relative terms, flow rate and flood risk variation due to climate change are estimated. In the specific case of Reinosa, the MRI-CGCM3 model shows that climate change will cause a significant increase of potential affected inhabitants and economic damage due to flood risk. This evaluation enables us to define mitigation actions in terms of cost–benefit analysis and prioritize the ones that should be included in flood risk management plans.

A Decrease in the Regulatory Effect of Snow-Related Phenomena in Spanish Mountain Areas Due to Climate Change

“…The motivation for using the ANA-MRI-CGCM3-rcp85 model results is twofold: (i) previous experience [4]; and (ii) current validation (Figure 2). Previous experience refers to a previous work carried out by the authors [4], where the analyses showed that this climate model achieved a good fit with real annual-average daily-flow-rates.…”

“…The motivation for using the ANA-MRI-CGCM3-rcp85 model results is twofold: (i) previous experience [4]; and (ii) current validation (Figure 2). Previous experience refers to a previous work carried out by the authors [4], where the analyses showed that this climate model achieved a good fit with real annual-average daily-flow-rates. Besides, before using the model again for this study, the authors checked and demonstrated, for the particular case of the Arga river basin (see Figure 2), that the validity of the ANA-MRI-CGCM3-rcp85 model predictions still stands.…”

“…Particularly, the increase in temperatures and decrease in average accumulations, or the delay in the accumulation of snow, may generate extreme events in which all the precipitation occur in liquid form (water), instead of part of the same being retained in the form of snow in the highest parts of mountains. This phenomenon has already happened in December 2019 in the town of Reinosa [4], which suffered the worst flooding in memory (return period estimated about 300 years) causing great damage and affecting residents.…”

“…Snow melting creates a set of water resources which need to be controlled and quantified, establishing their flow contribution to the rivers. Forecasting both variables, snowmelt and flow contribution, is important for the ordinary management that each Basin Organization performs and acquires great relevance for managing extreme hydrological phenomena, i.e., droughts and flooding, especially when trying to envisage and mitigate the damage they may cause [4][5][6][7][8].…”

“…Therefore, snow regulates the water resources of the country as it ensures a base flow in the rivers during the beginning of the summer period, which is characterized by low precipitation, high evapotranspiration and significant water demand. However, in certain specific weather conditions, such as a rapid increase in temperature combined with rains, significant melting of snow in short periods may occur, leading to high flows in river channels and causing flooding [4].…”