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About this website

About Overstroom ik

A large part of the Netherlands lies below sea level and many large rivers flow through the country on their way to the sea. More than half the population of the Netherlands lives in an area that is susceptible to flooding. Together with other water managers, Rijkswaterstaat works every day to protect our country from flooding. For instance, we reinforce the coast, maintain dykes and storm-surge barriers, and give more room to rivers. But nature is unpredictable, so things may still go wrong. To limit the number of casualties and material damage it is important that companies and residents know what they can do. Anyone can enter their post code on the Overstroomik.nl website and see the level to which the water could rise in their area. Is it possible to leave or is it wiser to stay after all?

Overstroomik.nl is produced by Rijkswaterstaat and the Ministry of Infrastructure and Water Management in collaboration with the Ministry of Justice and Security, the security regions, the water boards and the Delta Programme.

Explanation of the information on this website

The Overstroomik.nl website shows the consequences of large-scale flooding in the aftermath of a breach of flood barriers (e.g. dykes, dunes and locks) on the coastline, the major rivers or the smaller storage basins and lakes. This also includes flooding of unembanked alluvial areas. The site gives an indication of the maximum water levels in the
aftermath of a breach of the primary and regional flood barriers (dykes). The website also gives information on what you can do in this case. In the event of an actual crisis, the security region makes recommendations on whether to remain or leave.

Extreme situations

The water levels presented are based on extreme situations and give a picture of how high the water could rise in a worst-case scenario. The situation may be different during an actual flood event. Then we have a better idea of how much time is available, where the weaknesses are, how many people are in the area and which buildings and roads are available for evacuation. The Netherlands Water Management Centre  and the KNMI make an estimation of the expected water levels. The water manager assesses the current strength of flood defences. The various security regions outline the current options for evacuation. The security region reports on the current situation and advises residents.

The water levels are based on flooding scenarios made available at national level by the various provinces, water boards and Rijkswaterstaat, which are also used in the Climate Impact Atlas.

Dry places

The process of assessing where there are dry places (buildings) and the vulnerability of roads and railways is based on the relationship between the maximum water level and the Basic Register of Addresses and Buildings 3D model. This allows the impact of sloping roofs and the physical characteristics of the ground to be properly interpreted. In calculating whether any dwellings or other buildings have a usable storey that is dry, we have assumed that a storey is 2.65 metres high. This takes into account the fact that only storeys that can be used as shelter for several days at a time are counted. This may not be the case in reality. In the event of flooding we assume that the roads are under water and can no longer be used for evacuation.

Evacuation: the authorities' role and your role

The Netherlands is well protected against flooding. However, the flood defences might be breached (or come close to being breached) sooner or later. Under those circumstances, evacuation is a possible measure to limit casualties. The authorities have a role to play in this and will give information on any threat, and take measures to aid the evacuation. However, you will have to make your own way to safety.

Surface run-off flooding

Excess water is something that regularly arises, in the form of flooded cellars or standing water on roads. This can happen when there is heavy rainfall or because drainage ditches overflow. In all of these cases, the implications are less significant and profound than in the event of extreme flooding from the sea or rivers. The website does not give information on domestic flooding, high water-table levels, extreme pressure on the sewerage system or surface-water flooding.

Representative data

There are many different variations on the theme of flooding. There may also be a number of scenarios for the course of an evacuation. This website lists the current, state-of-the-art information on flooding and a possible action plan. A selection made from representative data that are relevant to preparations for flooding and water awareness. Design guidelines, classifications of possible combinations of drainage, wind and tides are used for this, as are estimations on the basis of traffic modelling and how people behave. This information has been carefully compiled and gives a picture of how it can happen.

The water levels presented are based on extreme situations and give a picture of how high the water could rise in a worst-case scenario. In practice, water levels may not be as high.

State-of-the-art knowledge

The information on this website is based on state-of-the-art knowledge and understanding. Errors may occur or information may be interpreted in different ways. The information on the website is updated on the basis of new knowledge and experience.

Climate Impact Atlas

Do you want to learn more about flooding? Then take a look at the Climate Impact Atlas website . You can find more information first and foremost in the 'Map Narratives' chapter. And not just about flooding, but also about other climate topics, such as excess water, heat and drought. A wide range of map layers are available in relation to this.