Code of conduct mowing

Why do we mow?

Every year we maintain our levees, ditches and grounds with Health . Mowing is important. In this way we prevent ditches from silting up and causing flooding or water shortages. In drought conditions, sufficient water can be supplied. On dikes it is important that the turf is strong. At the same time, many plants and animals live in ditches and on dikes. During mowing we take this into account. 

New rules starting in 2025

Since 2025 there is a new code of conduct Bestowing management and maintenance for water boards. This code of conduct contains agreements and rules for managing and maintaining ditches, dikes, (pumping station) grounds and maintenance paths. The Water Board and contractors who work for us must comply with these new rules. 

This way we not only ensure safe dikes and healthy waterways, but also better protection of nature in and around water and land. The code of conduct is in line with the 2024 Omgevingswet and its tightened rules. The new way of working took effect on April 1, 2025.

Tightening 

The water boards have tightened the habitat approach, a form of ecological management. For example, it is mandatory to conserve some of the plants in and along waterways. This strengthens the habitat of animal species that are under pressure, such as small mustelids, songbirds, raptors and owls. In addition, the code of conduct regulates more stringent scouting for birds and animals on site: "pre-running" mowing, depending on the location and situation on site. Phased mowing, i.e. not cutting everything short so that there is always room for animal species, is now a tougher requirement.

This changes for mowing ditches

Basically, we no longer mow ditches completely bare anywhere. Not even before winter. This means that we only completely mow one bank or ditch side. And on the other side we leave the vegetation on the bank or ditch side. We mow about 75% of the aquatic plants and 25% do not. Once a year we switch sides. We switch sides on July 15. If the left bank or ditch side is up this year, we 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, reduce algae and duckweed
  2. For fauna: frogs, fish, birds
  3. For flora: aquatic plants, reeds

This changes for mowing levees

We mow all grass dikes twice a year. During the first round of mowing, between June 1 and July 15, we leave half of the vegetation in place. Birds, amphibians, reptiles, butterflies and other species can settle or flee there. Before we mow the first round, the dikes are checked by ecological experts for breeding birds and other nests. Those nests are digitally marked and we mow around them. Or we don't mow that plot. We almost always dispose of the clippings as well. The second round of mowing takes place between September 1 and October 15. Then we mow the entire dike in order to inspect it.

Ecological management

Leaving vegetation in place year-round is a measure within the new code of conduct. In addition, we alternate mowing the bank or ditch edge where possible only after the breeding season. All kinds of animals and insects benefit from this. Think of breeding birds, amphibians and dragonflies that live in and around the water. 

If we do have to mow during the nesting season, we proceed carefully. Our field staff and contractors working for our water board pay close attention to the presence of nests. In the Netherlands, all breeding birds are protected. In places where we know there are breeding birds, we spare breeding birds and their nests. We do this by not mowing 10 meters around the nest. 

Preventing damage to plants and animals

Where we mow and perform maintenance, we must first check whether protected species are (or may be) present. Is that the case? Then we take protected plant and animal species into account as much as possible:

  • We take additional measures during the reproduction period, for example, mowing during a different period.
  • If we see nests, we mow around them.
  • Vegetation that does not impede water flow is left in place.
  • Fish that end up on shore we put back as much as possible.
  • We take into account the water temperature and take other measures to prevent fish mortality as much as possible.

Perhaps mow the same spot more often 

This new way of mowing causes us to come back to mow more often in some places. This way we make sure that the part of the watercourse that we mowed before actually stays open, so that the water can drain properly.

For more information on mowing ditches, levees and roadsides, see the Mowing page.