Nonstationarity in Flood Time Series

Flood hazard and arising risks due to associated vulnerabilities still appear to be among the common problems in today's hydrology in spite of highly motivated assessments and increasing knowledge and awareness as well as targeted measures for mitigation, preparedness, and emergency management. Beside the role of overall inaction, deficiencies in precautionary actions and presence of natural barriers and inaccurate or incomplete approaches in flood studies towards estimating flood magnitudes and frequencies are also assumed to have considerable impacts on limited control against the flood phenomenon. Prevalent claims about the invalidity of the stationarity assumption in hydrologic studies indicate any ignorance of nonstationarity as potential sources of ineffective flood assessments and the associated improper actions. The presented study investigates potential impacts and relative significance of observed trends on the magnitude and frequency of floods through comparisons performed over stationary and nonstationary flood frequency analyses. Results indicate slightly significant discrepancies between the estimates from both the stationary and nonstationary analyses by potentially pointing out to the arising needs for considering the nonstationarity in flood studies. (C) 2014 American Society of Civil Engineers.