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Unknowns: This type of development has not yet been
demonstrated in high-density cities. In fact, floating development
is just beginning to be thought of as a sea level rise strategy for larger
cities or islands. From an engineering perspective, many structures
can be built to float, though they cannot be retrofitted to do so. As
they have not been demonstrated anywhere as a model for high-
density cities, floating developments could end up facilitating growth
in parts of the country that are not close to jobs transit or services.
Floating infrastructure. The Lacey V. Murrow Memorial Bridge in CREDIT: PRASHKAN90, WIKIMEDIA FLOODABLE DEVELOPMENT
Washington connects Seattle and Mercer Island. It floats on Lake CREDIT: U.S. DEPARTMENT OF AGRICULTURE
Washington. What it is: Structures that are designed to withstand flooding or to
retain stormwater.
FLOATING DEVELOPMENT
The idea of floodable development is two-pronged. One idea is to
What it is: Structures that float on the surface of the water, or design buildings and infrastructure to resist damage by occasional,
may be floated occasionally during a flood—making them largely or even periodic, flooding. This could also be a back-up strategy in
invulnerable to changing tides. case shoreline armoring fails. A second idea is to create retention
areas for ocean surges or heavy rainfall. In those areas, water would
Floating homes can be moored to the shore or anchored to the be captured and then later released to receiving waters—or to the
sea floor. Floating development differs from boats in that it lacks wastewater system when floodwaters recede.
propulsion systems. The challenge of sea level rise has spurred
designs for floating forms of development that are much larger than Floodable development is an extreme form of low-impact
single-family homes, such as an offshore airport in the Netherlands’ development (LID). LID is a set of tools for beneficially reusing
North Sea and floating hotels and restaurants off of Dubai’s coast. stormwater by infiltrating it into the ground and creating green
Electricity, water and wastewater infrastructure must be supplied to space and habitat while reducing the demands on urban wastewater
floating development through flexible pipes. treatment systems. New floodable development built to handle sea
level rise may be designed to manage stormwater, both salt and fresh,
Examples at orders of magnitude above most LID tools.
Floating homes in Sausalito, where the first houseboat LID in action. This 12-acre constructed wetland provides wildlife
communities were established in the 1960s. Floating homes also habitat for migrating waterfowl and is a nesting area for animals.
are popular in other waterfront cities with relatively protected
waterfronts, such as Redwood City, Calif., Seattle and Amsterdam. Examples
Floating infrastructure. A floating greenhouse was built as a LID tools are widely used in Seattle and Portland, and are starting to
prototype in the Netherlands, and floating or pontoon bridges have come online in San Francisco. They include swales or contoured ground,
been built in several places in Washington. rain gardens, trees, constructed wetlands, green roofs and permeable
pavement. They also include large cisterns to store water for future
A floatable home prototype for New Orleans. A new home use. Floodable development, at a larger scale, is being pioneered with
designed to be used in New Orleans would rest on its engineered ideas such as landscape-scale flood parks, floodable streets (possibly
foundation most of the time. However, during a catastrophic flood channeled by temporary flood walls) and water plazas where floodwater
it could float as high as 12 feet, anchored to poles. rushes in to create an interesting feature in otherwise dry public space.
The Good, the Bad and the Unknown
Advantages: Floating development manages the uncertainty of
high tides and earthquakes. It could work in spite of the uncertainty
surrounding the timing and nature of sea level rise. Floating
development is very resilient to seismic activity.
Disadvantages: Floating development works only in protected
areas. Floating structures do not work well in places subject to wind
and wave action from storms, such as the ocean coastline.
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