The dynamics of peak head responses at Dutch canal dikes and the impact of climate change

Abstract. The management of water and flood risk levels in low-lying polder regions depends on the performance of canal dikes. Heavy rainfall can lead to peak hydraulic heads within the dikes affecting their stability, which can induce dike breaches. Variations in head responses and head statistics are both relevant for regional flood risk analysis of canal dike systems. This study examined the dynamics of peak heads in canal dikes on a national scale using time series models calibrated on observed heads. Various model structures are evaluated and a nonlinear model performed the best. These models were used to simulate long-term head time series. Subsequently, dike clusters were identified based on the coincidence of peak heads, allowing for the identification of dikes where peaks are caused by (dis)similar types of rainfall events. The differences and similarities in peak head response were related to physical dike characteristics. While no single significant relationship emerged, the soil type combined with the width of the dike appears to be important factors influencing the variation in head responses. However, the presence of the same soil type and dike widths in multiple clusters indicates that these characteristics do not yield a definitive outcome for the head response. Moreover, peak head statistics across various dikes were derived and indicated that extreme and yearly load conditions are relatively close to each other, with a median decimation height of only 15 centimeters. The head statistics are affected by climate change, characterized by increasing winter precipitation and summer evaporation. By 2100, extreme peak heads are expected to occur between 3 times less and 8 times more frequently, depending on the climate scenario and the type of canal dike.