Authors: Maddalen Mendizabal Roberto Moncho Peter Torp Contact: PhD. Maddalen Mendizabal Zubeldia ENVIRONMENT UNIT TECNALIA RESEARCH & INNOVATION Parque Tecnológico de Bizkaia. Edificio 700 E-48160 DERIO (Bizkaia) Spain

Abstract:
Inadequate management of forests for timber extraction, cattle farming, and abusive recreational practices together with the rapid urban sprawling, are factors creating significant problems in the Cantabrian area watershed regarding the sustainable management of the hydrological ecosystem services. These problems adding to the climate change consequences are already affecting on human and natural systems causing tangible and intangible damages. Particularly for this coastal area, flooding is necessary to analyze at local scale. Therefore, the impact of climate change on extreme precipitation and its influence on discharge is researched on the Atlantic climate basin within short rivers and fast flowing. In this paper, the ENSEMBLES RT3 climate model outputs are analyzed and calibrated with local observation data on a daily-based frequency.The hydrological/hydraulic coupling model (MikeShe-Mike11) is performed by forcing the validated model output.. For the spatial representativeness, basin and urban scales are studied. According to the results, under the medium greenhouse emission scenario (A1B), the Regional Climate Models HIRHAM (2001-2050 period) and RACMO (2051-2100 period) show an increase in the extreme precipitation. The expected changes have a spatial variability depending on the local characteristics (topography, proximity to the coast, vegetation, etc.) and ranging between 6-26 % for HIRHAM and 11-12 % for RACMO model. These changes in the precipitation affect the river flow. It is expected for the HIRHAM climatic model an increase of 22±2% for upstream peak discharge with a return period exceeding the 50 years. The change in precipitation causes an increase in the damage due to the flooding. This fact is the result of the expected change in the river’s peak flow by 2050 leading to an expansion of 3 % in the flood area as well as an impact on the degree of virulence. In this context, it has been necessary to define and assess the different adaptation options.