Katwoude dyke reinforcement

In 2006, approximately 33 kilometre between Hoorn and Amsterdam were rejected. The dike is currently being reinforced by the Markermeer Dike Alliance (AMMD). In 2011, other sections of dike along the Markermeer were also rejected, including two sections (modules 11a and 12a) around the Katwoude polder. These sections (modules) of the Katwoude project are surrounded by two modules of the Markermeer dike reinforcement project.

One polder. One project.

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

The water board has been working hard to fulfill this promise. And with success! Many different parties involved: the Markermeerdijken Alliance, the province of North Holland, the municipality of Waterland, the residents of the Katwoude polder, and HHNK have worked hard. On Tuesday, December 6, HHNK signed the contract with the Markermeerdijken Alliance. This brings the realization of '1 polder, 1 project' a lot closer.

Contact details for further information

With the assignment from HHNK to AMMD, environmental management will also be transferred to AMMD. In recent years, Wineke Straatsma and Joël Verstoep have been the contact persons (environmental managers) for modules 11a and 12a of the Katwoude dyke reinforcement project on behalf of HHNK. From now on, Doede Boomsma (AMMD) will take over. He was already the environmental manager for modules 11 and 12, which belonged to AMMD.

If you have any questions about the dike reinforcement, please contact Doede directly via email at d.boomsma@markermeerdijken.nl or on his cell phone at +31 (0)6-20 63 48 48. Alternatively, visit the website: www.markermeerdijken.nl.

Background information

Background information

The Markermeer dikes protect 1.2 million North Holland residents from the waters of the Markermeer lake. All dikes in the Netherlands are periodically tested for safety. In the second round of testing in 2006, approximately 33 kilometre the Markermeer dikes were rejected. These sections of dike are being reinforced in theMarkermeer dikes project. To this end, the 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 are among the dike sections rejected in the second assessment round in 2006 (see image modules).

During the 2011 assessment round, other sections of the Markermeer dikes were rejected. This concerns a 12. kilometre stretch of dike kilometre into four sub-areas: Volendam, Katwoude, Monnickendam, and Schellingwoude.

In 2019, the board of dike reeves and water board members (D&H) decided to tackle the Katwoude sub-area as a separate project. The aim is to accelerate the planning process for the dike sections along the Katwoude polder in order to keep pace with the Markermeer dikes project and thus retain the option of implementing both projects simultaneously.

Where is the project taking place?

Polder Katwoude consists of five modules in total. Module 11 'Pieterman' and module 12 'Katwoude' are part of the Markermeerdijken Alliance project. HHNK is tackling the other three modules to ensure that they are developed to the same level as modules 11 & 12. The HHNK modules are:

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

"In the eyes of the local community, the Katwoude dike reinforcement is a single project."

This is an important starting point for the HHNK project team. We are prioritizing the Katwoude sub-area in order to limit the disruption to the surrounding area and because of the synergy benefits of reinforcing a dike in one go. We are tackling this project in close collaboration with the municipality of Waterland, the Province of North Holland, and the AMMD.

What's going to happen?

In 2011, the dike sections of modules 11a, 12a, and 12b were rejected on the basis of stability on the inside and outside of the dike. In addition, the dike's revetment is not sufficiently sturdy in all places. 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 the exact reinforcement requirements for each subarea 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 inside of the dike is also insufficient, but on the outside it is sufficient in a number of places.

For module 12b, this section of the dike has only been rejected on the basis of its 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 preferred alternative ensures that the rejected dike sections once again meet all water safety requirements. The preferred alternative for modules 11a and 12a will now be further developed and optimized. In 2021, a draft Water Act project plan was drawn up describing the space required for the dike reinforcement and clarifying the effects and impact. The draft Water Act project plan was made available for inspection at the end of 2021 and no opinions were submitted.

Would you like to know what is involved in reinforcing a dike? You can find out in the book'DIJKEN voor beginners'(Dikes for Beginners).

Stone cladding

On the outside, the water side of the dike, there is stone revetment. This stone revetment protects the dike from waves and covers 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 once again meets current safety requirements. This means that, where necessary, the stone revetment will be replaced by concrete riprap (Basalton). The stone revetment will be slightly lower on the dike than it is now, reaching about halfway up the dike. To give you an idea of what the new situation will look like.

Opportunities for coupling

Implementation of local wishes 

In 2022, we continued to optimize the design. Discussions with local stakeholders (including the Katwoude working group) revealed three key wishes for the area. In jargon, we call these 'linkage opportunities'. We have licence elaborated on these linkage opportunities in anticipation of the licence , in order to provide an insight into what it will look like in the future. These relate to the layout of the road, the layout of module 12a outside the dike and the layout of 'de Kaap'. The opportunities for linkage have been elaborated in collaboration with the parties involved (including the Katwoude Polder Council, residents, other stakeholders, and government authorities). 

Improving traffic safety on Hoogedijk

Improving road safety is a strong desire of both 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 well-supported design will help with this transfer. In addition, it is wise to combine the road works with the dike reinforcement works. This way, once the dike reinforcement is complete, we will not only have a safe dike, but also a safe traffic situation. 

The municipality of Waterland is leading the road design in collaboration with HHNK (Water Safety & Roads department). At the beginning of 2021, residents' wishes and suggestions for the traffic layout of the Hoogedijk were collected. Where possible, these wishes have been incorporated into the draft design. 

On December 2, 2021, there was a walk-in consultation hour at the Katwoude Village Hall about the draft design for the traffic situation on Hoogedijk Katwoude. The design was also available on the websites of the municipality of Waterland and HHNK. Responses to the draft were welcome until the end of December 2021. Various responses were received, demonstrating a high level of engagement. In the document below, the municipality of Waterland responds to the questions and comments. 

The municipality of Waterland is currently working on the new design. As soon as it is ready, we will post it on the website.  

Katwoude: a unique location along the Markermeer dikes

The dike near the village of Katwoude has a unique location. This is due to the shelter created by the dike behind the foreland of Monnickendam and the dike to Marken. Due to this sheltered location and the 'flat berm', the dike has become overgrown over the years, making it an ideal place for swimming, boating, and gathering with the village. For the residents of Katwoude, it is important to preserve this added value after the dike reinforcement.

Wind direction and layout module 12a

Due to its sheltered location and the fact that the dike is not in the prevailing wind direction (southwest), the waves here crash less hard against the dike compared to other parts of the Markermeer dikes. 

This will make it possible to create a metre strip metre land in the future situation in order to preserve as much of the original character of the dike as possible. This will ensure that the dike continues to add value for residents even after it has been reinforced. 

The soil will be applied east of the House on the Water and west of Hoogedijk 35, a bed and breakfast outside the dike. In addition, metre will be dumped over the crumpled berm over a length of 50 metre . This will allow residents to safely walk over the sharp stones to go swimming.  

Photo of card showing the location of module 12a
Location 375 metre module 12a

Redesign of 'de Kaap'

In collaboration with the Katwoude Polder Council, Twiske-Waterland Recreation Authority, and Waterland Municipality, HHNK is redesigning 'de Kaap' near Jan Hagelhoek. Several sketching sessions have been held to increase social safety and recreational value. The recreational value of the cape can be increased and social safety improved by installing picnic tables, benches on the crest, additional steps, trash cans, and extra lighting.

What is the task and what is the most suitable solution?

Due to the current coronavirus measures, it is unfortunately not yet possible to share the information with residents at a residents' evening. To make the message a little more personal, the water board's environmental managers, 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 provides the project team with the outer parameters of what the dike will look like. In the coming period, we will work out more and more details and draw up the planning documents (studies) required to apply for the licence. The wishes and requirements previously gathered from the local community will be incorporated as far as possible. We will involve local residents in the next steps. Once there is more clarity about the planning, we will inform local residents.

Research and reports

Newsletters and communication

Involving the community

Working group

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

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

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