Abstract
This study investigates and compares several design storms for flood estimation in partially urbanized catchments. Six different design storms were considered: Euler II, alternating block method, average variability method, Huff’s curves, and uniform rainfall. Additionally, two extreme historical storms were included for comparison. A small, ungauged, partially urbanized catchment in Novigrad (Croatia) was chosen as a study area to account for the infiltration impact on the rainfall-runoff process. The performance of each design storm was assessed based on the flood modeling results, namely the water depth, water velocity, flow rate, and overall flood extent. Furthermore, several rainfall durations were considered to identify a critical scenario. The excess rainfall was computed using the Soil Conservation Service’s Curve Number method, and two-dimensional flooding simulations were performed by the HEC-RAS model. The results confirmed that the choice of the design storm and the rainfall duration has a significant impact on the flood modeling results. Overall, design storms constructed only from IDF curves overestimated flooding in comparison to historical events, whereas design storms derived from the analysis of observed temporal patterns matched or slightly underestimated the flooding results. Of the six considered design storms, the average variability method showed the closest agreement with historical storms.
Highlights
Prediction of flood hazards is a crucial part of flood risk assessment, flood risk management plans, and the design of flood protection measures
The results confirmed that the choice of the design storm and the rainfall duration has a significant impact on the flood modeling results
This study investigated and compared several design storms for the purpose of estimating flooding in partially urbanized catchments
Summary
Prediction of flood hazards is a crucial part of flood risk assessment, flood risk management plans, and the design of flood protection measures. Because of a strongly interconnected rainfall-runoff process, as well as a rapid advancement of computational technology and the availability of high-resolution topographic data [3], pluvial floods are simulated using integrated hydrological-hydraulic methods consisting of time-dependent 2D models and so-called rain-on-grid approaches [2,4,5,6,7]. There are two main approaches for flood assessment in ungauged catchments—the event based and the continuous-simulation method [12]. The event based methods simulate rainfall-runoff transformation of a design rainfall hyetograph of a given duration and return period [13], whereas the
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