Cluster showers and flooding 

Nuisance caused by flooding

When locks, streams, or canals overflow their banks, or when a dike breaks, flooding causes damage. Fortunately, this happens very rarely. When it does happen, the water board takes action to solve the problems.

Disruption after heavy rain

During a downpour, a large amount of rain falls in a small area in a short period of time. Often, all that water cannot be drained away immediately and remains on the streets or land. Basements can get wet and, in the worst case, the water can enter the house. This is because cities often have a lot of hard, stony surfaces: sidewalks, streets, buildings, and parking lots. These surfaces do not allow rainwater to pass through. Agriculture also suffers greatly from overly wet soil. 

When it rains very hard, a lot of water flows from roofs and roads into the municipal sewer system. Sometimes the sewer system cannot cope with this. And then water flows from the sewer into a ditch, stream, or canal, or onto the street. We call this a sewer overflow.

Groundwater flooding

When is it flooding?

Does an average of 10 liters of water per square meter fall within 24 hours? Then the municipality's sewer system must be able to handle this. Flooding of up to 15 cm once every two years is still reasonable. Adjacent buildings should remain dry, as the floor level is normally 5 cm higher.

Up to six times a year, overflow of excess sewage may occur in a separate sewer system. In such a system, dirty water from households is discharged separately from (clean) rainwater. Because overflow can affect the quality of surface water, large basements are sometimes constructed to temporarily collect sewage. The dirty water can then still be discharged via the sewer system. This prevents it from ending up in surface water.

Why are heavy downpours a problem for the sewer system?

During heavy downpours, a large amount of precipitation falls in a short period of time. The sewer system cannot handle so much water at once. This can cause drains to overflow and streets to become temporarily flooded. It can also lead to sewer overflows.

How does rainwater cause nuisance?

Due to overflow in a combined sewer system

During heavy rainfall, the capacity of the sewer system is sometimes insufficient. The sewer system can then no longer cope with the amount of rainwater. Even manhole covers can be lifted by the water pressure from the sewer. This results in overflow. The excess rainwater (mixed with wastewater) then flows directly from the sewer into surface water. Or it ends up on the street. This can lead to traffic disruption, especially in urban areas.

Due to flooding

Nuisance can also arise when ditches and ponds fill up and overflow their banks . Or when rainwater remains on the streets (which is better than the water flowing into homes).

What do we do in the event of flooding?

Is there so much rain that flooding is occurring? Then we will take action to combat it. How we do this is set out in our emergency plan. This also specifies who we consult with and how we inform our community and the media. More information:

• Emergency