If frequent flooding becomes a problem with sea level rise and storm surges, an external barrier to prevent water damage to buildings will be the best solution for buildings that have a watertight foundation.[1] When considering building flood barriers, the two most effective options are levees or floodwalls. Levees would create a barrier by excavating an area and building a gradual incline with earthen materials. Generally, Levees are significantly less expensive than floodwalls. However, they require lots of land space, imported soil, – since MIT is in an urban environment – and erode more quickly with frequent flooding than floodwalls.[2] A floodwall is constructed using brick, concrete, or masonry and is more resistant to erosion than natural soil. (See the image below for an example of an effective urban floodwall). A floodwall could be 1-20 feet high depending on the assessed need although the practicality and effectivity of the design usually limits a wall to 4 feet. Beyond that height, the wall would need to be fortified to withstand increased pressure of floodwaters by increasing the depth which would make the wall significantly more expensive as well.[2] The general estimates of costs for floodwalls are $92/linear foot for 2 foot floodwalls, $140/linear foot for 4 foot floodwalls, and $195/linear foot for 6 foot floodwalls.[2] When building floodwalls, engineers must assess the basement foundation and soil to determine how far away from the building the floodwall must be so the pressure on basement walls does not cause the foundation to crack, buckle, or collapse.[2] With these considerations taken into account, floodwalls are very effective solutions in protecting a building from water damage during flooding and area able to surround an entire building.
Figure 1: Floodwalls like this one can be designed to be retractable and can be raised when expecting a flood instead of building a permanent wall. This is often a good solution for urban environments.
Source: Spring Dam[3]
By Geneva Casalegno
References
- Packard, Director of Utilities at MIT, K. (2017, November 15). MIT Utilities Systems Overview [Personal interview].
- FEMA. (n.d.). Chapter 5 – Barriers. Retrieved November 23, 2017, from https://www.fema.gov/media-library-data/20130726-1608-20490-6445/fema551_ch_05.pdf
- Spring Dam. (2017). Retrieved November 29, 2017, from http://aquobex.com/products/products-filter/