The BBC reported (https://www.bbc.co.uk/news/av/world-europe-26302176/flood-proof-homes-the-dutch-way) that they are about 20% more expensive to build, but bear in mind that the land value makes up a significant part of the cost of a home, so the total property price would be less than 20% (for example 10% if the land value is half the property value). This is further offset by much reduced insurance and cleanup costs. With that in mind it seems quite sensible and possible to follow their example.
Christopher Gillie ● 1998d