# A Systematic Review: To Increase Transportation Infrastructure Resilience to Flooding Events
## 2 Materials and Methods  
This review utilized Google Scholar and Scopus to search for scholarly articles and papers published from 1900 to 2021. Google Scholar searches scholarly literature from articles, theses, and books from multiple publishers, societies, and repositories. It was chosen as a widely used starting ground for scientific research [12]. Scopus is a database of peer-reviewed literature that is collected from journals, books, and conferences regarding science, technology, social sciences, arts, and humanities. It was chosen as it represents a main data source for over three thousand academic and corporate institutions [13]. The results found from these searches were very widespread from a variety of major journals, databases, and websites including: SpringerLink, ASCE, MDPI, Sage Journals, ScienceDirect, and Wiley Online Library. Result totals mentioned below are equivalent to the sum of both database searches' results together. An advanced search was used by one independent reviewer with the criteria of: (1) custom range in the beginning of the review from 1900 to 2021 for Google Scholar and 1961 to 2021 for Scopus since Scopus does not provide data from 1900 to 1960, (2) exclusion of citations and patents results in Google Scholar, and (3) search keywords in the title of the article in both Scopus and Google Scholar. Citations and patents were excluded as these represented sources without publication access and patents were not the format represented in studies for this review. The search criteria within Scopus were limited to article title and within Google Scholar to title only to exclude results of which the topic was not the primary focus. A variety of publications were accepted including articles, journal papers, reports, and theses until the third stage in which only peer-reviewed journal publications in English were considered. As aforementioned, this review contained three stages. Each stage's key features can be seen in Figure 2 and each is explained in greater detail below. As mentioned previously, this review initiated with a search to find which natural hazard or natural disaster was most studied regarding vulnerability. Stage one conducted a search with seventeen natural hazards and natural disasters as mentioned above, and the word 'vulnerability,' since vulnerability refers to a possible level of destruction due to a natural disaster. Table 1 presents the number of studies found with each type of natural hazard or natural disaster; a total number of 6541 results were found from all natural disaster vulnerability studies. As seen in Table 1, the amount of studies related to natural hazard and natural disaster vulnerability was nearly zero from 1900 to 1980, but it began to increase from 1981 to 1990. This can be likely attributed to two factors: the increase of occurrence of several natural disasters and efforts to prepare and respond to natural disasters, such as the development of corporations that initiated extensive amounts of studies [14]. Since the 1980's, large corporations including the Centre for Research on the Epidemiology of Disasters (CRED) and the US Agency for International Development (USAID) initiated efforts to investigate natural disasters [14]. These two factors could be linked with climate change, as the early 1980's felt increased temperature and the late 1980's  
Figure 2: Detailed Framework of this Systematic Review. experienced drought and wildfire, and the Intergovernmental Panel on Climate Change was formed in 1989 [15]. As seen in Table 1, 'flood vulnerability' was the most prominent with 2223 results, which confirmed this as the most decisive direction to conduct the rest of the review. The next highest was 'drought vulnerability' with 1383 results, and all others had lower result totals. Since studies regarding the vulnerability of floods represented the natural disaster with the highest amount of studies from a total of seventeen natural hazard and natural disaster vulnerability searches, flood was chosen as the natural disaster to further investigate.