# A Systematic Review: To Increase Transportation Infrastructure Resilience to Flooding Events
## 2 Materials and Methods
Figure 3 presents a similar trend as all natural hazards and natural disasters observed; flood vulnerability studies also increased rapidly after the 1980's. Therefore, the authors further focused on the time frame of database from 1981 to 2021 to conduct the remainder of this review. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Natural Hazard or** & **1900–1960** & **1961–1980** & **1981–1990** & **1991–2000** & **2001–2010** & **2011–2021** & **Total** \\
**Disaster Type** & & & & & & & \\ \hline Avalanche & 0 & 1 & 0 & 0 & 13 & 21 & 35 \\ Drought & 1 & 2 & 12 & 39 & 164 & 1165 & 1383 \\ Earthquake & 0 & 4 & 19 & 49 & 232 & 973 & 1277 \\ Extreme Temperature & 0 & 0 & 0 & 0 & 0 & 25 & 25 \\ Flood & 0 & 1 & 4 & 26 & 236 & 1956 & 2223 \\ Hail & 0 & 0 & 1 & 0 & 2 & 8 & 11 \\ Heat wave & 0 & 0 & 0 & 0 & 8 & 52 & 60 \\ Hurricane & 0 & 0 & 1 & 3 & 89 & 260 & 353 \\ Ice storm & 0 & 0 & 0 & 0 & 0 & 1 & 1 \\ Landslide & 0 & 0 & 2 & 3 & 49 & 374 & 428 \\ Lightning & 0 & 8 & 10 & 2 & 10 & 29 & 59 \\ Strong wind & 0 & 0 & 0 & 0 & 2 & 4 & 6 \\ Tornado & 0 & 0 & 0 & 0 & 11 & 45 & 56 \\ Tsunami & 0 & 0 & 0 & 5 & 141 & 357 & 503 \\ Volcanic activity & 0 & 0 & 0 & 0 & 9 & 5 & 14 \\ Wildfire & 0 & 0 & 0 & 0 & 9 & 93 & 102 \\ Winter weather & 0 & 0 & 0 & 0 & 0 & 5 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Natural Hazard and Natural Disaster Vulnerability Study Results over Time from both Google Scholar and Scopus. Figure 3: Flood Vulnerability Study Results over Time from both Google Scholar and Scopus. With stage two, this review persisted to find which infrastructure was most studied with flood resilience. Resilience is one of the key aspects to consider with floods since it accommodates proper management of floodwater during flooding events which lessen risk to people and infrastructure [16]. Increasing resilience is crucial to ensure the well-being of communities that are affected by flood events, and infrastructure is a component that affects resiliency of the communities. To influence resilience of communities, infrastructure handles, withstands, and restores operability to floods and thus requires alterations, changes, and proper development to handle these events. Since climate change has increased the intensity and frequencies of floods, infrastructure resilience is a high priority. This study considered critical infrastructure including the chemical, commercial facilities, communications, critical manufacturing, dams, defense industrial base, emergency services, energy, financial services, food and agriculture, government facilities, healthcare and public health, information technology, nuclear, transportation, and water and wastewater systems sectors [17]. Stage two used the keyword phrase 'flood resilience infrastructure.' Results from the search keyword phrase 'flood resilience infrastructure' totaled to 79 results. 55 results were considered since 24 results were repeated between the two databases. Each study was screened, and these 55 studies were categorized by the primary types of critical infrastructure which were involved in the study: transportation, wastewater treatment, water supply, energy, green infrastructure, health care, housing, communications, and emergency services. Transportation was focused on in 57% of these studies, wastewater treatment in 42%, energy in 34%, water supply in 32%, green infrastructure in 23%, health care in 21%, communications in 21%, housing in 19%, and emergency services in 8%. Many articles featured more than one type of infrastructure, so total percentages are not one hundred. Since transportation was the most prevalent infrastructure type, this was considered in relation to floods and resilience studies for the rest of the review. In stage three, this study searched literature related to transportation infrastructure resilience to flood events. Based on titles and abstracts, final keywords (i.e., 'transportation', 'road(s)', and 'transit' with 'flood' and 'flooding') were determined.