Valkenhorst area development

A new residential neighbourhood, Valkenhorst, comprising 5,600 homes and associated amenities, is being developed on the site of the former Valkenburg Naval Air Base. The Central Government Real Estate Agency commissioned Iv to deliver a range of design services for this area development project. These included the preparation of a strategic water management plan, a strategic sewerage plan, and a geohydrological assessment of the development area. Particular emphasis was placed on the interaction between surface water and groundwater, together with the future-proof integration of the water system.

The work was carried out in close collaboration with the key stakeholders, including the Municipality of Katwijk and the Rijnland Regional Water Authority. This collaborative approach enabled an integrated way of working from the outset, ensuring that water, soil and spatial development were considered as one coherent system.

The construction of the new homes and amenities will significantly increase the amount of hard surfacing across what is currently a largely undeveloped site. As a result, the natural infiltration of rainwater will decrease, causing runoff to reach surface water or the sewer system more quickly, increasing the risk of localised flooding.

Most of the project area was not connected to a sewer network. The new development will therefore include a completely new separate sewerage system together with a wastewater pumping station for foul water. Various system options were assessed during the design process. For one of the first times in the Netherlands, the Rijnland Regional Water Authority made climate resilience requirements mandatory for a large-scale area development project. This called for a system capable of accommodating intense rainfall while remaining resilient during prolonged periods of drought. The principle of water and soil as guiding principles also formed a key basis for the spatial design of the development.

This project supports the delivery of much-needed new homes while combining residential development with sustainable, climate-resilient water management. Starting with an assessment of the existing water system, the sewerage infrastructure and the interaction between groundwater and surface water, the project has progressed towards an area development with a robust and future-proof water system.

The result is a sustainable, climate-adaptive development that reflects the ambitions of modern blue-green infrastructure projects, where water, green space and urban development are integrated into a single, coherent design. This creates a living environment in which sustainability, flood resilience and spatial quality go hand in hand.