Combining Continuous and Event-based Hydrological Modeling in Kävlinge River Basin with HEC-HMS

Sammanfattning: Prediction of flood and evaluation of the impact of climate change in a catchment needs to be correctly estimated, which can be accomplished by hydrological modelling in HEC-HMS. In this paper, the objectives were to gain an understanding of the rainfall-runoff process and estimate the flood frequency curve in the Kävlinge River Basin. However, due to the complexity of a catchment, models should be well-calibrated and validated in order to increase predictive ability. The flood frequency estimation through simulation can be addressed through continuous or event-based hydrological modelling. Firstly, because of the data availability for short-term storms and initial soil moisture conditions, continuous models are calibrated and validated in different years. Afterwards, the identical parameters can be used for the event-based simulation. The hypothetical storm method was used to construct flood frequency curves of different return periods. Finally, all the above simulations were carried out with climate change scenario RCP8.5. The result shows that the Curve Number (CN), initial abstraction (Ia) and Lag time are the crucial parameters for the rainfall-runoff modelling. The statistical analysis of Coefficient of Determination (R2), Percent Bias (PBIAS) and model Peak error (%) efficiency criteria were used for performance evaluation at three stations (Högsmölla, Ellinge and Vombsjön). Most of the statistics are within an acceptable range (±30%) except the values at Vombsjön due to the regulated flow, which indicates the good performance of the hydrological modelling. As well as this, the hydrological model with RCP8.5 climate change scenario is used to evaluate the effects of climate change on continuous and flood events simulation. There are around 24% and 20% increases in peak flow respectively compared with the current condition.