Moving a building out of the existing flood hazard area is the safest solution among several retrofit-ting methods; however it is also usually the most expensive method (FEMA, 2009). When a community acquires a flood-prone home from the owner, relocation is often applied, as well as demolition of the building. The relocation is not only limited to buildings, it can also be applied to other exposed coastal infrastructure.
Relocation includes the following process: lifting up a building from its foundation, placing it on a trailer, transporting it to a new safe area, and setting it onto a new foundation. As with the elevation of a building, a relocated building must be structurally sound enough to withstand all the stresses during the relocation process. Similar techniques as used for the elevation of buildings are used for lifting and setting a building structure. The moving process requires trailer wheel sets to be placed beneath steel beams supporting the building. The size and weight of a building affects the relocation process and the necessary equipment. A single- story, wooden framed building with a rectangular shape is easier to be relocated than a multi- story, solid masonry one.
Given that relocation requires a moving route between the old and new sites, this adds additional consideration because of the route restrictions, such as width of roads, load limits on bridges, and clearance of facilities along the route. If a building is too large to fit on any moving route, it may be cut into sections, moved separately, and reassembled at the new site. Taking public roads and changing utility lines requires the necessary permits from local governments or utility companies. The relocated building also needs to meet all zoning ordinances and building codes in the new site.
Because relocation is a costly but effective method to prevent recurrence of flood damage, it is often used for preserving historical buildings and monuments. The City of Grand Forks, North Dakota, USA was severely hit by the Red River flood in April 1997 (FEMA, 2001). The Boomtown Building, one of the city’s oldest structures and a property of the National Register of Historic Places, was also a casualty of the flood. In order to make way for a new dike, the building had to move to another location with the financial support of the city.
Another famous example of relocation of an historical monument is shown by the Abu Simbel tem-ples in Egypt. Following the rise of the Nile waters as a result of the construction of the Aswan High Dam, a multinational team of archaeologists, engineers and skilled heavy equipment operators working together under the UNESCO banner, began in 1964 the salvage of the Abu Simbel temples. Between 1964 and 1968, the entire site was carefully cut into large blocks (up to 30 tons, averaging 20 tons), dismantled, lifted and reassembled in a new location 65 meters higher and 200 meters back from the river, for a total cost of some USD 40 million at the time (De Carvalho, 1966).
- In areas with low population densities, the costs of retreat (including compensation and infrastructure costs) could be significantly less than other grey or green measures to protect assets where they are.
- The retreat of settlements and infrastructure can be combined with the recreation of natural features, such as vegetation buffers, wetlands, dunes, that can provide landscape and biodiversity benefits as well as protection against erosion, debris flows and floods.
- Retreat policies are likely to be more successful and receive stronger public support if they are designed in a long-term perspective.