Flood Risk Modeling under Uncertainties: The Case Study of Croatia

This study presents an approach for assessing the flood risk using the fully probabilistic description of the annual damage using the derived higher-order statistical moments of the annual damage random variable. The annual damage distribution is used to analyze the impact on the macro-scale agglomeration described with the unified damage function in the case study of the river Kupa, Croatia. The agglomeration damage function is derived through the unit damage function and estimated distribution of building thresholds within the studied agglomeration. The unit damage is described with the shape function, which can easily accommodate different forms of damage assessment depending on the available information. The estimated distribution of annual maximum flood levels is propagated through the agglomeration damage function into the annual damage distribution derived using higher-order statistical moments and presented with the exceedance probability, indicating the likelihood that a certain annual maximum damage can be exceeded. Besides the aleatory uncertainty of annual maximum flood levels, we analyzed the impact of the uncertainty in estimating the unit damage function upon the annual damage distribution. This uncertainty shows a significant impact on the shape of the annual damage distribution, particularly in the region of extreme flood events. Analyzing the annual damage distribution range, resulting from the uncertainty in damage functions, provides more information to policymakers in assessing the potential consequences on the future spatial planning programs, particularly from the strategic environmental assessment point of view.