THE EFFECT OF MIXED PEAK DATA ON THE FLOOD QUANTILE ESTIMATES IN A SINGLE STATION ANALYSIS: CASE STUDY
In the flood frequency assessment, engineers often face the problem of mixed peak data in the data record: some peaks are instantaneous daily flows (IDF), while the others are mean daily flows (MDF). If the problem is recognized, correction factor to the MDFs in the dataset is usually applied. In our research, we use flood flow datasets from 8 hydrologic stations with catchment area up to 1000 km 2 in the Sava River basin. Four hydrologic stations are located in Bosnia and Herzegovina (BiH) and four in Serbia. We apply Sangal’s procedure to establish a correction factor for a single station analysis to produce the IDFs from MDFs. We use three annual maxima datasets at each hydrologic station, comprising: 1) IDF only, 2) MDF only, and 3) mixed IDF and MDF (officially available). We subject each dataset to flood frequency assessment using USACE HEC-SSP Bulletin 17b and 17c analysis. The results show the diversity of flood quantile estimates at each station, with the most significant differences obtained according to expected probability curve in Bulletin 17b analysis. The highest uncertainty shown as mean square error of skewness coefficient is observed at stations with large data gaps, and large number of detected low outliers. The case study revealed a potential for significant underestimation or overestimation of flood