Water Resources and Flood Hazard Assessment with Consideration of Anthropic Effects

Studies on water resources are rarely developed in basins where anthropic impact is negligible; therefore, the flow values are seldom ''natural'' and are often significantly affected by the interference of human works. These alterations of the natural discharges can be due to the presence, along the river network, of interfering hydraulic structures. Interactions between these infrastructures and the natural streamflow are certainly in need of further attention. Two main issues have been studied here in detail: i) the impact on water availability and the variability caused by water abstractions and ii) the flood attenuation effect induced by existing reservoirs, that produces flood hazard mitigation downstream. When working in a regional analysis framework, input data and results should represent the natural conditions. Hence, the alterations due to hydraulics structures embedded into the river network should be removed or introduced carefully. For instance, regional estimates of flood peak discharges do not consider the flood attenuation operated by the existing reservoirs. Nevertheless dams have a significant impact, especially in the nearest areas downstream, that should be accounted for. For the Piemonte and Valle d'Aosta Regions, this flood peak attenuation effect has been studied in detail to provide a correct starting point for further flood hazard studies. On the other hand, to assess the impact of water abstractions on daily discharge data, basic indices of alterations have been defined and an innovative correction model to reconstruct the natural streamflow statistics has been proposed. Non-impacted discharge characteristics are needed to provide a correct regional estimate of water resources availability and, consequently, of the gross hydropower potential. For water use planning purposes or to define the residual hydropower potential, the correction model proposed can also be used backward, adding anthropic effects to non-impacted values of discharge. The relevance of the proposed approach and methods in regional analysis of extreme and average flows is something that can be better recognized only with the effort of systematically characterizing the infrastructures that interfere with the natural hydrology along the river network. The applications made in this work were made possible by a cooperative effort addressed to the realization of a comprehensive Hydrological and Infrastructures Information System for the Regione Piemonte, that constitutes an important laboratory for hydrological simulations in a real world of heavily altered natural processes.