Influence of floating housing on water quality and ecology in The Netherlands

Abstract – Large floating projects have the potential to overcome the challenge of land scarcity in urban areas and offer opportunities for energy and food production, or even for creating sustainable living environments. However, they influence the physical, chemical, biological and ecological characteristics of water bodies. The interaction of the floating platforms affect multiple complex aquatic processes, and the potential (negative/positive) effects are not yet fully understood. Managing entities currently struggle with lack of data and knowledge that can support adequate legislation to regulate future projects.

In the Netherlands the development of small scale floating projects is already present for some years (e.g. houseboats), as well as some floating communities that are already built (e.g. floating neighborhood at IJburg). Multiple existing floating buildings from different regions of the Netherlands were considered as case-studies for a data-collection campaign using different monitoring methods and technologies.

To obtain data and images from underneath floating buildings, an underwater drone was equipped with cameras and sensors. The drone was used in multiple locations to scan for differences in concentrations of basic water quality parameters (e.g. dissolved oxygen, electrical conductivity, nutrients) from underneath/near the floating structures, which were then compared with data from locations far from the influence of the buildings. Underwater drones also collected images of the benthic layer under the houses, and of the surface of the houses to assess the sediments and benthic communities along selected transects. Continuous data was also collected over several days using multi-parameter water quality sensors permanently installed under floating structures. Additionally, numerical models were used to quantify the influence of certain effects, such as wind-tunnel effect and underwater shading.

Results show some differences in concentrations of water quality parameters between open water and shaded areas were detected, and some interesting relations between parameters and local characteristics were identified. Recommendations are given, in order to minimise the undesired impacts of floating platforms. Considering the complexity of the interactions between water quality parameters and the influence of the surrounding environment it is recommended to continue and to improve the monitoring campaign (e.g. include new parameters).