Flooding – Flood probability of primary and regional tides (2020)

Since 2019, DPRA has been advising the new map ‘Place-related flooding opportunity’ for the theme of Flood Control. The map provides insight into the chance of a flood with a water depth > 20 cm and thus provides a better insight into flood risks than just the maximum water depth maps, which only present the “horror image” of the maximum water depths (the most extreme event). In this map, the flooding opportunities of the primary and regional barriers are combined. The ‘place-based flooding opportunity’ will help in the topic of consequential flood reduction. The primary and regional barriers protect the hinterland from flooding. The primary barriers have a standard that indicates the probability of failure per dike trajectory. On the basis of these standards, the flood scenarios are derived and have an exceeding frequency equal to or less than the standard. The regional fences are based on an overrun rate of 1/100 years. It may occur that certain hinterland locations are likely to be hit by more than one flood scenario. When this happens, the likelihood of these specific locations being affected by a flood increases. That’s why it’s called place-related flooding opportunity.