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

Abstract

Managing the water and flood risk in low-lying polder regions depends on the performance of canal dikes. This performance is influenced by hydraulic heads, which can peak due to heavy rainfall, affecting their stability and potentially inducing dike breaches. Variations in head responses and head statistics are 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 a unique dataset of head observations across the dike system. Various model structures were evaluated, and a non-linear model performed the best. These models were used to simulate 30 years of head time series representing current and future climate scenarios. 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 between dikes and identified clusters were related to physical dike characteristics. While the subsurface material and dike width appeared to influence the head response variation of clusters, their presence across multiple clusters indicates that they do not yield a definitive outcome. Moreover, peak head statistics across various dikes indicated that extreme and yearly occurring load conditions are relatively close to each other, with a median decimate height of only 15 cm. With climate change driving higher winter precipitation and summer evaporation, head statistics are changing. 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.