Safety Analysis of the ComCoast concept, Comcoast WP 3

ComCoast COMbined functions in COASTal defence zones is a European project which develops and presents innovative solutions for flood protection in coastal areas. The ComCoast concept is designed to develop alternative defence systems and new sustainable flood management strategies to cope with increasing hydraulic loads. The objective of this research is to give a safety assessment for different configurations within the ComCoast concept. The model that has been developed is capable of calculating the failure probabilities of different ComCoast concepts. Since the calculations are based on a two-dimensional representation of a Coast-configuration the results of the calculations give an order of magnitude of the failure probability of the ComCoast concepts. It must be noted that the calculations are based on the assumption that the primary dike and the secondary dike are infinitely strong. Consequently, failure due to instability, erosion and piping is neglected. For the two case studies given both the failure probabilities and applicability of the ComCoast-concept differ significantly. A comparison is made between the two case studies for the situation where both cases just meet the required standard. This means a crest level of 8.4m NAP for the Hondsbossche Zeewering case and a crest level of 6.8m NAP for the Perkpolder case (Variant 2). The comparison shows that very little water enters the transitional area in the Perkpolder case. On average there will be an inundation depth of 0.01m every 300 years, whereas in the situation of the Hondsbossche Zeewering this inundation depth will occur on average every 4 years. Since one of the aims of the ComCoast concept is to create a wetland (transitional area) behind the primary dike, a ComCoast option seems less suitable for the Perkpolder case. The main reason why the return periods of inundation depths are long in the Perkpolder case is that the wave climate at Perkpolder is moderate. Overtopping mainly occurs with a high water level, which goes hand in hand with high return periods.Civil Engineering and Geoscience

Safety Analysis of ComCoast Concept at Nessmersiel

This report provides a safety analysis of the ComCoast concept at Neersiel in Germany. The ComCoast concept is to use a wide coastal area for water defence purposes. The wide coastal area can be referred to as a coastal defence zone. The primary dike will be provided with a overtopping resistant revetment allowing more seawater to overtop the dike and the area behind the primary dike will be used to store overtopping seawater.Civil Engineering and Geoscience

Veiligheidsberekening van het ComCoastconcept op Breebaart-polder

Dit rapport beschrijft een veiligheidsanalyse van het ComCoast-concept voor de BreeBaart-polder te Groningen. Het ComCoast-concept gaat uit van een brede waterkering, waarbij de primaire dijk overslagbestendig is en de achterliggende polder wordt benut voor het opvangen van het overslaande water.Civil Engineering and Geoscience

How safe are Dikes during Flood Waves? Analysis of the Failure Probability of Dike Ring Areas in Flood Wave Situations

Civil Engineering and Geoscience

Stand van zaken rond waterveiligheid in Nederland

Vorig jaar kwamen de resultaten van de derde landelijke toetsing van de veiligheid van de primaire waterkeringen beschikbaar. Ongeveer eenderde van de meer dan 3.700 km dijken en duinen voldoet niet aan de normen. Er bestaat dus een aanzienlijke opgave om de keringen te laten voldoen aan de huidige normen. Deze krijgt vorm in het (nieuwe) hoogwaterbeschermingsprogramma. Daarnaast wordt in het deltaprogramma uitgewerkt hoe de overstromingsrisico’s in de toekomst beperkt kunnen worden. Nieuwe inzichten in dijksterkte en meerlaagsveiligheid krijgen hierin een belangrijke plek.Hydraulic EngineeringCivil Engineering and Geoscience

Application of Fragility Curves in Operational Flood Risk Assessment

The aim of this article is to present and discuss fragility curves that were derived for numerous dikes in the Netherlands within the Dike Data Service Centre (DDSC) initiative. A fragility curve of a dike is a mapping from the set of loads, acting on the dike, to the set of conditional dike failure probabilities. The DDSC is a platform around a database for measurements related to water defences in the Netherlands. The measurements include real-time and historical data such as height measurements, pore water pressures, temperature etc. Besides the database functionality, the DDSC can be applied to interpret the information and issue warnings. The fragility curves were derived for failure mechanisms overtopping, piping and macro-stability as well as for combination of these mechanisms. Also, application of the fragility curves is addressed. The application includes: (i) insight into the effect of reducing uncertainties in subsoil-related parameters on the dike's reliability, (ii) derivation of the actual flooding probability and the actual local mortality risk, and (iii) prioritization of emergency flood measures. The derived fragility curves are conform findings of past studies: for water levels lower than the dike height, piping and macro-stability play an important role. Furthermore, the fragility curves prove to have an added value in operational flood risk assessment