Flood damping by reservoirs: proposition of a graphical parametric method

ABSTRACT Flood reduction constitutes an important characteristic of surface reservoir design. Thus, to ensure that minimum safety standards are met, the Safety Dams Act was approved in 2010. Many multipurpose surface reservoirs are aging and getting out of the current technical standards. In Ceará State, Brazil, there are several dams built for many decades, with spillways sized by empirical formulae which are currently outdated. This article contributes to improve the understanding of the morphological and hydrological factors involved in the process of damping floods in reservoirs and the development of a simple application method that estimates the damping, from such factors. To do so, hydrological simulations of several scenarios representative of reservoir and hydrographic basins configurations were performed. As a result, the impact of each parameter on flood damping was determined. A graphical method was proposed in which all the morphological parameters of the basin and the reservoir were aggregated into a single dimensionless parameter - the Reservoir Damping Index (Φ). With the value of Φ calculated, it is possible to estimate the damping capacity of the reservoir. This method can be used for the design of new reservoirs or for the verification of reservoir spillways already constructed with other methodologies.