3.1.3. Wet Flood-Proofing

Wet flood-proofing measures allow floodwater to enter a building but limit the damage to the structure and its contents (Figure 1). This minimizes the risk that the walls of the house will collapse due to hydrostatic pressure from rising floodwaters on the outside. Measures include, for example, building utility installations and high-value areas above flood levels, raising electrical sockets, fitting tiled floors so that the building can quickly be returned to use after the flood, and sealing walls with water-resistant building materials [16]. For an extended table of individual flood-proofing measures, see Appendix B Tables A2 and A3. Construction cost for wet flood-proofing are presented in Table 3 and range between \$2412 for residential structures and \$34,070 for office buildings. The cost for flood-proofing office buildings is usually higher, as office buildings are relatively large, and the value of building contents is higher than that of residential buildings. Wet flood-proofing the basement of a residential building costs around \$35–206/m2. Maintenance costs are low—estimated at <1% of the total investment cost [26]. The cost of flood-proofing a 1500-L oil tank against buoyancy, buried in the garden, is estimated at \$1550 [27].

Brazil Residential n.a. \$962 2010 \$1024 n.a. [35] Vietnam Residential (60 m2) +1 m \$248 2014 \$273 n.a. [18] P Germany Oil tank Proofing against buoyancy \$1210/tank 2011 \$1550 n.a. [27] P
