Code of conduct for mowing

Why do we mow?

Every year, we carefully maintain our dikes, ditches, and land. Mowing is important. It prevents ditches from becoming overgrown and causes flooding or water shortages. In case of drought, sufficient water can be supplied. It is important that the grass on dikes is strong. At the same time, many plants and animals live in ditches and on dikes. We take this into account when mowing. 

New rules from 2025

Since 2025, there has been a new code of conduct for sustainable management and maintenance for water boards. This code of conduct contains agreements and rules for the management and maintenance of ditches, dikes, pumping station sites, and maintenance paths. The water board and contractors working for us must comply with these new rules. 

In this way, we not only ensure safe dikes and healthy waterways, but also better protection of nature in and around the water and land areas. The code of conduct is in line with the Omgevingswet 2024 and the stricter rules that accompany it. The new working method came into effect on April 1, 2025.

Tightening 

The water boards have tightened up the habitat approach, a form of ecological management. For example, it is now mandatory to spare some of the plants in and along the water. This strengthens the habitat of animal species that are under pressure, such as small mustelids, songbirds, birds of prey, and owls. In addition, the code of conduct stipulates that more rigorous checks must be carried out to determine whether birds and animals are present at a location: 'scouting' before mowing, depending on the location and the situation on site. Phased mowing, i.e. not cutting everything short so that there is always room for animal species, is now a stricter requirement.

This is what will change for mowing ditches

In principle, we no longer mow ditches completely bare anywhere, not even for the winter. This means that we only mow one bank or ditch edge completely and leave the vegetation on the other bank or ditch edge untouched. We mow about 75% of the aquatic plants and leave 25% unmowed. We switch sides once a year. We do this on July 15. If it is the left bank or ditch side's turn this year, we will mow the right bank or ditch side next year. We call this phased maintenance. 

Why phased maintenance? For three reasons:

  1. Aquatic plants improve water quality and reduce algae and duckweed.
  2. For the fauna: frogs, fish, birds
  3. For the flora: aquatic plants, reeds

This is what will change for mowing dikes

We mow all grass dikes twice a year. During the first mowing round, between June 1 and July 15, we leave half of the vegetation standing. Birds, amphibians, reptiles, butterflies, and other animal species can settle there or flee there. Before we start mowing the first round, the dikes are checked by ecological experts for nesting birds and other nests. These nests are digitally marked and we mow around them. Or we don't mow that plot at all. We almost always remove the cuttings. The second mowing round takes place between September 1 and October 15. We then mow the entire dike so that we can inspect it.

Ecological management

Leaving vegetation untouched throughout the year is one of the measures included in the new code of conduct. In addition, where possible, we only mow the banks or ditch edges after the breeding season. This benefits all kinds of animals and insects, such as breeding birds, amphibians, and dragonflies that live in and around the water. 

If we do have to mow during the breeding season, we proceed with great care. Our field staff and contractors working for our water board pay close attention to the presence of nests. All breeding birds are protected in the Netherlands. In areas where we know there are breeding birds, we spare the breeding birds and their nests. We do this by not mowing metre 10 metre the nest. 

Preventing damage to plants and animals

Where we mow and carry out maintenance, we must first check whether protected species are (or may be) present. If this is the case, we take protected plant and animal species into account as much as possible:

  • We take extra measures during the breeding season, for example by mowing at a different time.
  • If we see nests, we mow around them.
  • We leave vegetation that does not impede water flow in place.
  • We release as many fish as possible that end up on the shore.
  • We take water temperature into account and implement other measures to prevent fish mortality as much as possible.

Perhaps mow more often in the same spot 

This new mowing method means that in some places we have to return more often to mow. This ensures that the part of the watercourse that we mowed earlier remains open, allowing the water to drain away properly.

For more information about mowing ditches, dikes, and roadsides, see the Mowing page.