Dike reinforcement Katwoude

In 2006, about 33 kilometers of dike between Hoorn and Amsterdam failed. The dike is currently being reinforced by the Alliantie Markermeerdijken (AMMD). Other dike sections along the Markermeer were also rejected in 2011, including two dike sections (modules 11a and 12a) around the Katwoude polder. These dike sections (modules) of project Katwoude are surrounded by two modules of the project dike reinforcement Markermeerdijken.

One polder. One project

In 2017, the board of HHNK made a promise to the municipality of Waterland and the residents of polder Katwoude. We are organizing the various dike reinforcements around this polder in such a way that it feels like one project to the area. One polder, one project! A beautiful promise, but quite a challenge.

The Water Board has energetically set to work to fulfill this promise. And with success! Many different parties involved: Alliantie Markermeerdijken, province of North Holland, municipality of Waterland, the residents of polder Katwoude and HHNK have worked hard. Tuesday, December 6 was the signing of the contract award from HHNK to the Alliance Markermeerdijken. This brings the realization of '1 polder, 1 project' a lot closer.

Contact details for more information

With the assignment of HHNK to AMMD, the environmental management also transfers to AMMD. In recent years, Wineke Straatsma and Joël Verstoep have enjoyed being the contact persons (environmental managers) for modules 11a and 12a of dike reinforcement Katwoude on behalf of HHNK. As of now, Doede Boomsma (AMMD) is taking over. He was already environmental manager for modules 11 and 12 that belonged to AMMD.

For questions about the dike reinforcement, please contact Doede directly at email address: d.boomsma@markermeerdijken.nl or at his mobile number: 06-20 63 48 48. Or check the website: www.markermeerdijken.nl.

Background information

Background information

The Markermeer dikes protect 1.2 million North Hollanders from the water from the Markermeer. All the dikes in the Netherlands are periodically tested for safety. In the second assessment round in 2006, approximately 33 kilometers of the Markermeer dikes failed the test. These dike sections are being reinforced in the Markermeer Dikes project. To this end, the high water board has entered into an alliance with Boskalis/VolkerWessels under the name Alliantie Markermeerdijken (AMMD). Dike sections 11 (Pieterman) and 12 (Katwoude) in the Katwoude polder belong to the dike sections that were rejected in the second review round in 2006 (see figure modules).

During the 2011 assessment round, other dike sections of the Markermeer dikes were rejected; this involved a dike section of 12.5 kilometers divided into four subareas: Volendam, Katwoude, Monnickendam and Schellingwoude.

In 2019, the College of Dike Counts and Higher Water Boards (D&H) decided to take up sub-area Katwoude as a separate project. The purpose of this is to accelerate the planning for the dike sections along the Katwoude polder in order to stay connected to the Markermeer Dikes project and thus keep the possibility of executing both projects simultaneously.

Where does the project take place?

Polder Katwoude consists of a total of five modules. Module 11 'Pieterman' and module 12 'Katwoude' are part of the Markermeer Dikes Alliance project. The remaining three modules are being picked up by HHNK to ensure that they are at the same level of elaboration as module 11 & 12. The modules of HHNK are:

  • module 11a 'Jan Hagelhoek';
  • module 12a 'West side Katwoude';
  • module 12b 'Nieuwendam' .

"The dyke reinforcement of Katwoude is one project in the eyes of the environment," he said.

This is an important starting point for the project team at HHNK. We are giving priority to the Katwoude subarea in order to limit the inconvenience to the nearby area and because of the synergy benefits of reinforcing a dike all at once. We are tackling this project in good cooperation with the Municipality of Waterland, the Province of North Holland and the AMMD.

What will happen?

In 2011, the dike sections of modules 11a, 12a and 12b were rejected for internal and external dike stability. In addition, the dike revetment is not strong enough everywhere. The three animations below show how a dike can fail in terms of stability and revetment:

Additional studies of the dike were conducted in 2018 and 2019. Based on these studies, we determined exactly what the reinforcement task for each subarea is for the next 50 years. This means that module 11a is not stable enough on both the inside and outside of the dike. In module 12a the stability on the inner side of the dike is also not sufficient, but on the outer side it is in a number of places.

For module 12b, this part of the dike has only been rejected for revetment. The repair of the revetment will be coordinated with the work on the Monnickendam pumping station and the modification of the N247 by the province of North Holland.

The chosen preferred alternative ensures that the rejected dike sections once again meet all the requirements of water safety. The preferred alternative for modules 11a and 12a will now be further elaborated and optimized. A draft project plan under the Water Act was drawn up in 2021, describing the land take of the dyke reinforcement and providing insight into the effects and impact. The draft Water Act project plan was made available for inspection at the end of 2021 and no views were submitted.

Do you want to know what is involved in a dyke reinforcement project? You can find out in the book 'DIJKEN voor beginners'.

Stone cladding

On the outside, the water side of the dike, is stone revetment. This stone revetment ensures that the dike is protected from waves and lies up to three-quarters of the dike. It is an important part of a safe dike. The stone revetment is currently partially hidden under vegetation that has grown over and between it over the past 100 years. As part of the dike reinforcement, we are ensuring that the stone revetment will again meet current safety requirements. This means that, where necessary, the stone revetment will be replaced with a concrete facing (Basalton). The stone revetment will be slightly lower on the dike than the current situation, up to about halfway along the dike. To give you an impression of what the new situation will look like.

Co-op opportunities

Elaborating wishes from the environment 

In 2022, we continued to optimize the design. Discussions with the surrounding area (including the Katwoude working group) revealed three important wishes for the surrounding area. In jargon, we call these co-option opportunities. In anticipation of the permit we have already worked out the details of these co-opportunities in order to provide a glimpse of what it will look like later. This concerns the layout of the road, the layout of module 12a outside the dike and the layout of 'de Kaap'. The coincidental opportunities have been worked out in collaboration with the parties involved (including Polderraad Katwoude, residents and other interested parties and government authorities). 

Improve traffic safety Hoogedijk

Improving traffic safety is a strong desire of both the residents and the municipality of Waterland. The road along the foot of the dike (the Hoogedijk) is largely managed by HHNK. Only the built-up area falls under the management of the Municipality of Waterland. HHNK intends to transfer the roads in this area to the municipality. A good and supported design helps with this transfer. In addition, it is smart to combine the work on the road with the work on the dike reinforcement. This way, when the dike reinforcement is completed, we will not only have a safe dike, but also a safe traffic situation. 

The Municipality of Waterland is leading the design of the road in cooperation with HHNK (Department of Water Safety & Roads). At the beginning of 2021, residents' wishes and suggestions were collected for the traffic design of Hoogedijk. These wishes were worked into the concept design, if possible. 

On December 2, 2021 there was a walk-in meeting in the Dorpshuis Katwoude about the draft design of the traffic situation Hoogedijk Katwoude. The design could also be found on the websites of the Municipality of Waterland and HHNK. Comments on the concept were possible until the end of December 2021. Several responses were received which showed great involvement. With the document below, the municipality of Waterland responds to the questions and comments. 

Currently, the Waterland Municipality is working on the new design. As soon as that is ready, we will post it on the website.  

Katwoude: a unique place along the Markermeer dikes

The dike near the village of Katwoude has a unique location. This is due to the lee that arises because the dike lies behind the foreland of Monnickendam and the dike to Marken. Because of this sheltered position and the "flat shoulder," the dike here has overgrown over the years, making it an ideal place for swimming, boating and gathering with the village. It is important for the residents of Katwoude to retain this added value after the dike reinforcement.

Wind direction and layout module 12a

Due to the sheltered location and because the dike is not in the prevailing wind direction (southwest), the waves here do not hit the dike as hard compared to the other parts of the Markermeer dikes. 

This makes it possible to realize a strip of land over a length of 375 meters in the future situation to preserve as much as possible the original character of the dike. In this way, the dike will retain its added value for residents even after the reinforcement. 

The soil will be applied, east of the House on the Water and west of Hoogedijk 35, outside of the dike B&B. In addition, sand will be deposited over a length of 50 meters over the crush berm. This will allow residents to safely walk over the sharp stones for swimming.  

Photo of map showing location of module 12a
Location 375 meters in module 12a

Refurbishing 'the Cape'

In cooperation with the Polderraad Katwoude, recreation board Twiske-Waterland and municipality Waterland, HHNK is working on the redesign of 'the Cape' at Jan Hagelhoek. Several sketch sessions have been held to increase social safety and recreational value. By realizing picnic tables, benches on the crest, extra steps, wastebaskets and extra lighting, the recreational value of the cape can be increased and social safety increases.

What is the task and what is the best-fit solution?

Unfortunately, due to the corona measures in place, it is not yet possible to share the information with residents at a residents' evening. Nevertheless, to make the message a little more personal, the environmental managers of the high water board, Wineke Straatsma and Joël Verstoep, have recorded a short vlog. On location, they explain how we arrived at a preferred alternative for modules 11a and 12a.

 Preferred alternative module 11a, Jan Hagelhoek

Preferred alternative module 12a, Katwoude west side

What does this mean for me?

The preferred alternative gives the project team the outer framework of what the dike will look like. In the coming period, we will work out more and more details and the plan products (studies) needed to apply for the permit will be prepared. The previously collected wishes and requirements from the surrounding area will be incorporated as well as possible. The residents in the area will again be included in the next steps. When there is more clarity about the planning we will inform the residents in the area.

Surveys and reports

Newsletters and communication

Involving the environment

Working Group

To come up with appropriate ideas that are not only safe but also fit into this unique environment, the help of a working group is needed. To arrive at a preferred alternative, the Water Board organized several design sessions in a working group. The working group consisted of members of the project team of HHNK/AMMD (designers, technical advisors), employees of the municipality of Waterland, the province of North Holland, recreation board Twiske Waterland and residents and entrepreneurs from polder Katwoude.

The working group has been closely involved in the process of arriving at suitable solutions for dike reinforcement and choice of the preferred alternative (the most appropriate way to reinforce the dike)

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