Elevating houses to address flood risks: A detailed analysis

Elevating structures is a method that is widely utilized (especially in the United States) to tackle flood impact. However, the factors that control the benefits of this approach over its financial costs is an issue that has not been thoroughly investigated.

As flood incidents have increased both in numbers and intensity, owners tend to elevate their properties in order to withstand a potential incident. According to the U.S. Federal Emergency Management Agency (FEMA), the elevation suggested should be adequate to deal with the 100-year flood (a flood incident that has 1% to occur annually) that a region will experience. Nevertheless, there are many uncertainties that should be taken into consideration and this guideline is considered a simplification.

Scientists from Pennsylvania State University, have made a thorough investigation to present the framework under which the proper house elevation can be derived with better accuracy. Their findings were recently published in Nature Communications.

The study focuses on the U.S. where a great proportion of the population lives in regions prone to flooding. The benefits of buildings' elevation are challenging to derive due to multiple uncertain inputs including the structural damage that a flood may cause, the life span of the building, the discount rates etc. The team investigates those inputs in an effort to assess and quantify their effect by using mathematical models. "It is arguably better to fail in a computer model than in real life. In the computer, we can look at many possible future outcomes of flooding, costs and other uncertainties," Mahkameh Zarekarizi, lead author of the study and a Postdoctoral Scholar at Pennsylvania State University, stated.

The study emphasizes the important sources of uncertainties and improves the level of decision making by analyzing:

• Deep uncertainties
• The interactions on decision objectives and 
• The trade-offs between multiple stakeholder objectives

The regional and flood characteristics along with the features of buildings were taken into consideration in the models utilized. 

According to the findings of the study, the elevation levels suggested by FEMA and neither optimal nor cost-efficient in all cases. In total, buildings should be raised a few feet above the FEMA's suggestions so that long-term damages would be mitigated.

The impact of the input uncertainties is crucial and can completely change the risk management strategy that should be developed in a given area. Authors deduce that a well-established technique to evaluate engineering, social and ground interactions is critical to derive the best solution for any case.

The findings of the study can be applied in regions outside the United States, given that certain modifications in terms of uncertainties quantification would be applied. Authors suggest that there is still much more scientific work to be conducted in this field in the future. "Our study is subject to several caveats that point to future research needs," the study, mentions.

Sources: Nature Communications, PSU