Assessing lithological uncertainty in dikes: Simulating construction history and its implications for flood safety assessment

Abstract

Dikes often have a long history of reinforcement, with each reinforcement adding new material resulting in a heterogeneous dike. As data on the dike internal heterogeneity is sparse, it is generally overlooked in the stability assessment of dikes. We present an object-based and process-based model simulating dike construction history on archeological dike cross, yielding similar patterns of heterogeneity as observed in real dikes, and apply it in a dike safety assessment. Model predictions improve when being based on more accurate statistics of dike buildup, or when being conditioned to ground truth data. When incorporated in a dike stability assessment, multiple model runs can be coupled to hydrological simulations and dike slope stability calculations, resulting in a probabilistic stability assessment considering internal dike heterogeneity. While high-resolution observations are still sparse, good model accuracies can be reached by combining regional information on dike buildup with local point observations and this model provides a parsimonious basis to include information of internal dike heterogeneity in safety assessments.

Causes of dike deterioration – environmental and anthropogenic effects

“…The dike system construction began more than 150 years ago. Since it has been continuously raised and strengthened (Nagy 2006), this has resulted in a heterogeneous, so-called onion structure documented by a few authors (Tóth-Nagy 2006;Schweitzer 2009; van Woerkom et al 2022;. The embankments are mainly constructed from materials locally available ( van Woerkom et al 2022), using historic construction methods (Dyer-Utili-Zielinski 2009), such as cross transportation.…”

“…Since it has been continuously raised and strengthened (Nagy 2006), this has resulted in a heterogeneous, so-called onion structure documented by a few authors (Tóth-Nagy 2006;Schweitzer 2009; van Woerkom et al 2022;. The embankments are mainly constructed from materials locally available ( van Woerkom et al 2022), using historic construction methods (Dyer-Utili-Zielinski 2009), such as cross transportation. The flood protection embankments bear many construction errors like unsuitable earthwork materials, inadequate compaction, and unfavourable subsoil conditions.…”

Confronting complexity

“…Yang et al (2022) show how floods influence the behaviour of companies and how this cascades through supply chain disruptions. Van Woerkom et al (2022) show an example of the legacy effect of past flood risk management practice and how it influences today's risks.…”