Frequently asked questions

Do you have a question about Overstroomik.nl? Then check whether the question is answered on this page first. For any other questions you may have, just contact Rijkswaterstaat.

Why is it important for me to know how high the water level could rise where I live?

More than half of the population in the Netherlands lives on land that could flood. For that reason, the government works to protect our country from high water levels every day. But nature is unpredictable, so things may still go wrong. Overstroomik.nl shows you how high the water level could rise for each postcode area in the Netherlands and what everyone can do to limit damage and casualties if there is a threat of flooding.

Now that I've looked at the Overstroomik.nl website, I know that the water level where I live will rise by 2 metres if there is a flood. What does Rijkswaterstaat do in that case?

Rijkswaterstaat works every day to protect our country from high water levels by building and maintaining flood barriers such as dams and dykes. If ever things go wrong, the result could be flooding. At that point, the security region (regionally coordinated emergency-response team) takes control, implements measures and notifies local residents. Rijkswaterstaat provides the security regions with information and advice from the Netherlands Water Management Centre. Rijkswaterstaat also manages traffic movements in the event of evacuations using the motorway network.

Does Overstroomik.nl continue to give information during a flood event?

No, Overstroomik.nl was created to raise awareness of the possibility of flooding in your area and gives you tips on what you might want to do. Then you know what to expect if there is a flood event. If the roads outside are actually under water, the security region will update you on the situation via NL Alert, crisis.nl and the emergency broadcast stations.

The website isn't working properly

I get no result when I fill in my post code.

This system is linked to the system operated by the various municipalities. It may be the case that your post code has not been entered into the system due to a recent reorganisation at municipal level, or because your house is in a new neighbourhood. If you'd like to know straight away how high water levels could rise in your area, you can also search using GPS on your mobile device.

I've filled in my post code or GPS location, but the website is showing me the name of the municipality.

That's correct; however the website shows the water level that matches the post code or GPS location.

NAP (Amsterdam ordnance datum): the information on the website doesn't match my situation

Our house is 4 metres below NAP. The website shows that water levels will rise just 0.5 metres here. That can't be right.

NAP is not the sole factor that determines the water level in the event of an actual flood event. In larger regions, for instance, a low-lying area will not fill with water evenly like when you fill a bathtub, for example. The amount of water that flows into an area is limited. One of the reasons for this is the (limited) length of time that water levels in a river or at sea remain high. Elevated roads, the rise and fall of the landscape and local dykes all also have an influence on how the area floods.

The image of the dwelling for the post code I've entered does not match the actual situation. I don't live in a two-storey house.

To show the flooding, we use a schematic representation of a small house gradually flooding, a two-storey house with an attic room. The calculation of whether or not your house has a storey above the water level is based on information that we obtain from the Land Registry (Kadaster). We use an indicative height of 2.65 metres for each storey to determine how many storeys a building has. In reality, the height of individual storeys may vary, leading to a slight difference.

I live on a house boat (or another type of dwelling).

The image shows a schematic representation of a house. The calculation of whether or not your house has a storey above the water level is based on information that we obtain from the Land Registry (Kadaster). In this case, we have not taken special situations such as yours into account. We use an indicative height of 2.65 metres for each storey to determine how many storeys a building has. In reality, the height of individual storeys may vary, leading to a slight difference.

The arrow on the map is not pointing to my home.

The arrow indicates a point in the middle of the post code area. If you are using GPS, the droplet will be on the exact location where you are now.

The result where I live is different to where my neighbours live. That house is the same as ours, and built on the same level.

To calculate the extent of the flooding we use blocks of 100 square metres. We assume an average ground level for the entire block. So it may be the case that two dwellings that are close to each other fall into different blocks and, as a result, give different results.

The red and green spots for dry storeys don't correspond to my home.

The spots are indicative: they show where there are houses with a dry storey (green) and where there are houses without (red). The calculation of whether or not your house has a storey above the water level is based on information that we obtain from the Land Registry (Kadaster). We use an indicative height of 2.65 metres for each storey to determine how many storeys a building has. In reality, the height of individual storeys may vary, leading to a slight difference.

What is the basis for the water levels?

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 National Water and
Flooding Information System (LIWO) and the Climate Impact Atlas . In some areas that might include water from the coast and, also, water from the rivers.

What factors have been taken into account when calculating water levels in the event of flooding?

The website shows the consequences of large-scale flooding in the aftermath of a breach of the (primary) flood barriers (e.g. the dykes) on the coastline and the major rivers and the regional flood defences. This also includes flooding of unembanked alluvial areas. Problems posed by water and surface run-off other than large-scale flooding occur more frequently, such as 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.

The information on the website 'stops at the border'. But borders do not hold back rivers and water. It goes without saying that we work together with other countries to give the Netherlands the best protection against water. That will also be the case in the event of an actual flood event. This website is designed to be used with addresses in the Netherlands. The website that caters for addresses in Belgium is waterinfo.be. Germany does not appear to have a nationwide website for water information.

Just before and during a flood event

If there is a threat of flooding, the security region will notify me. Who is behind the security region?

The security region is the driving and connecting force that coordinates aid, disaster relief and crisis management in a particular region. It is a collaborative effort between municipalities, the fire service, police, medical assistance and the ambulance service.

In the event of a flood event there will be no electricity and the internet will be down. What use is a website under those circumstances?

Overstroomik.nl was created to make you aware of the risk of flooding in your vicinity and gives you tips on what to do. Overstroomik.nl was created to raise awareness of the possibility of flooding in your area and gives you tips on what you might want to do. If the roads outside are actually under water, the security region will update you on the situation via NL Alert, crisis.nl and the emergency broadcast stations.

What do I have to do in the event of an evacuation?

This website gives no information on precisely what you must do if there is an evacuation in your region. In the event of flooding and evacuation, the security region will provide you with information. This website gives you the opportunity to form a picture of the extreme conditions that you can expect and the precautionary measures you can take.

Will I be able to get away if water levels haven't risen very high?

A car cannot be driven once the water has reached a level of 15 cm.

Will I still be able to get away when the water is coming my way?

In the event of flooding, the water level may not have peaked where you are, but levels may rise further along your route. A car cannot be driven once the water has reached a level of 15 cm. Your life is in danger if the water takes you by surprise on your escape route. The security region provides information on evacuations.