Floating Communities: A Solution to Rising Sea Levels?

With rising sea levels accompanying climate change, and a shortage of developable land in rapidly urbanising regions, are floating cities a feasible solution?

Several Floodlist articles highlight populated areas in the world that are repeatedly flooded, some with increasing frequency. These are often located in river deltas or floodplains where water velocities during flooding not particularly high, and where communities are relatively tight-knit and well-established. Due to the large areas and populations involved, relocation is not a feasible option for a number of reasons, not limited to costs.

Floating Villages

There are, in fact, several examples of communities of ‘boat people’ that have grown into sizeable floating towns, Aberdeen floating village in Hong Kong, Makoko village in Nigeria, and Sausalito, California, to name but a few better-known examples. These villages are generally made up of house-boats, which are limited in size and function – although Makoko village is renowned for the erstwhile floating school designed and built by architect Kunlé Adeyemi.

In the Netherlands, however, the concept of floating villages has been taken to a different level with the Waterbuurt (pdf) (Water District) floating neighbourhood, part of the IJburg islands development.

Credit: Wojtek Gurak / Flickr, Under CC BY-NC 2.0

IJburg Islands Development, Amsterdam

With the fast pace of population growth in the capital city of Amsterdam over the last few decades, land for new housing is scarce, and much of it, like the rest of the city, is below or at sea level. New suburbs like Almere and Lelystad, both built on reclaimed land between 1960 and 1990, were built on the outer edge of the city, and fed urban sprawl with its associated costs and inefficiencies.

IJburg, however, sees the city taking a new direction, with the development of a series of islands in the IJmeer ‘lake’ to the east of the city centre. The first of a series of ten new man-made islands emerged in 1997 using a ‘pancake’ method of building up the lake floor in layers with dredged sand, and the first housing appeared in 2002. By 2015, six of the islands had been completed. These islands are some of the few areas in Amsterdam where houses are actually situated above sea level!

Commencement of the four remaining islands (IJburg II) was delayed because of concerns regarding proposed zonings and ecological impacts. Following a year of consultations, the revised project framework plan was approved in 2015, although completion of the last island is only expected in 2026. According to Feargus O’Sullivan, writing in CityLab, “That pause between phases of constructing the IJburg islands was arguably beneficial because it allowed some key concerns about the program to be heard. Most of these focused on the IJmeer Lake itself. A vital habitat for birds, it’s a wide-open space that a crowded, densely built-up country like the Netherlands can ill afford to spoil.”

The overall IJburg development will consist of 18,000 residential units and 12,000 commercial/office premises. 30% of the residential units will be ‘affordable’ rental housing’, and 30% ‘middle income’ rental housing, with the remainder privately owned.

‘Waterbuurt’ Floating Neighbourhood

In addition to the new islands, the developers decided to ‘test the waters’ with a floating neighbourhood made up of two-, three- and four-storey floating homes connected together and linked to the land by a network of floating walkways.

The ‘Waterbuurt’ development, designed by Dutch firm Architectenbureau Marlies Rohmer (AMR), consists of 55 floating homes, with a further 20 units on built partly on land and partly on stilts overhanging the water. The gross floor area of the 75 units is 10,625 square metres (114,367 square ft), and the development has a potential total of 165 units. The floating housing units were constructed at a boat-building facility some 65km (40 miles) away, and towed across the lake to their present position at Steigereiland (Jetty Island) in IJburg.

“We could build the houses very quickly, because the shipyard was covered, so weather didn’t matter,” said Rohmer in a 2011 interview with DeutscheWelle (English), “It’s an ideal place to build.” Each unit could be completed in a time period of about 4 months.

Credit: Wojtek Gurak / Flickr, Under CC BY-NC 2.0

The housing units are built of a lightweight steel frame with wooden or synthetic panelling, all on a floating concrete ‘basement’. The tub-shaped basement (or caisson), which sits mostly under the water-line, usually accommodates the unit’s bedrooms. The water around it moderates the interior temperature, improving energy efficiency by 15% and reducing the need for air-conditioning with its associated operational costs.

AMR designed the rental units, which are all similar in style and colour, while the designs of the individually owned units are done by architects chosen by the owners. The cladding on the rental units are all white, Marlies Rohmer says “”When designing I had a cheerful fleet of white tupperware-boats in mind”.

Owing to the size of the boat-builder’s dock and the width of the intervening series of locks, each unit is too narrow, at 6.5m (21 ft) wide, to provide sufficient stability in water to accommodate the height and mass of the taller homes. To achieve adequate stability, these are fastened together in tandem with steel plates at their final mooring site to create larger, wider homes. Each unit is attached by sliding collars to two poles sunk into the lake bottom, to prevent lateral drifting, while permitting vertical movement with changes in the water level.

Individual floating homes range in floor area between approximately 170m² (1,830 square ft) and 275m² (2,960 square ft), with a 50-year lease for the water area on which they are moored. Apart from separate registration of both the water area lease and the dwelling itself (as a vessel), agreements needed to be reached regarding responsibility for maintenance of the walkways and the services, as well as on the design of service connections to the floating homes.

The water area in which the houses float is cut off from the rest of IJmeer by a dike and a lock, creating its own small harbour and minimising the effects of wind-driven swells and storm surges. The cost of a floating home in Waterbuurt is about the same as that of a similar sized dwelling elsewhere in Amsterdam’s newer suburbs (about €464,000 or US$500,000), but few are as easily accessible from the city centre as this floating community.

Situated just a 15 minute tram ride from the centre of Amsterdam, the IJburg development provides housing that is safe from sea level rise, while at the same time avoiding urban sprawl.

Real World Example

Whilst a number of architects that have designed high value single floating homes, and there is no shortage of futuristic schemes for floating cities, Architectbureau Marlies Rohmer’s Waterbuurt is a real-world example of relatively affordable mixed housing of a type that can be replicated in other parts of the world. It still, however, represents a type of housing that is well beyond the affordability level of flood-prone communities in many parts of the world, and the search for innovative low-cost solutions continues.

Credit: Wojtek Gurak / Flickr, Under CC BY-NC 2.0