Testing the relationship between instantaneous peak flow and mean daily flow in a Mediterranean Area Southeast Spain

Extreme hydrologic events have great importance in Southeastern Spain regarding the personal and economic damage they imply. The commonly-used design parameter for hydraulic structures is the maximum annual instantaneous stream flow recorded in conventional gauging stations. However, the majority of available data in Southeastern Spain is mean daily stream flows. This paper explores possible linear relationships between annual instantaneous peak discharge (IPF) and the corresponding (MDF) mean daily stream flow. This relationship was previously explored by other authors such as Fuller [Fuller, W.E., 1914. Flood flows. Trans. Am. Soc. Civ. Eng., 77: 564–617]. Non-linear responses of IPF–-MDF were observed in several study basins. The use of Principal Components Analysis (PCA) allowed characterizing the most important topographic and hydrological attributes of the basins and provided important information about variables that should be included in IPF–MDF regional equations. The key factor to justify the different IPF–MDF relationships in a relatively small area is the nature of the extreme events and their effects on semi-arid soil conditions. In addition, a regional equation to estimate IPF from MDF was developed. This equation was applied to a series of flow of nine stations of the Southeast Basin of Spain, and a significant improvement was achieved when applying this formula in comparison to the traditional method of Fuller. This study indicates possible restrictions to take into account when traditional hydrological model are applied in semi-arid areas.