Flood Assessment Based on a 500-year Flood Event in the City of Syracuse

Onondaga Creek flows through the center area of Syracuse, the fifth biggest city in New York State, with one-third of the 145,000 population living within the Onondaga Creek watershed. To understand the potential risk of flooding in the floodplain of Onondaga Creek and its impact on other parts of Syracuse, this research attempted to accomplish the flood hazard assessment for a previously simulated 500-year flood event in the downstream floodplain of Onondaga Creek within Syracuse. The assessment consisted of three parts. The first part was the flood vulnerability assessment. Based on the existing knowledge of flood characteristics reported in earlier studies regarding its physical, social, and economic impacts, eight commonly used vulnerability indicators, including Digital Elevation Model (DEM), slope, distance to Onondaga creek, vegetation, population, economic status, land use/cover, and buildings are selected and measured for the study area (i.e., Syracuse). Fuzzy Analytical Hierarchical Process (FAHP), a new machine learning method that is more accurate and objective than the traditional Analytical Hierarchical Process (AHP) method, was subsequently used to calculate the individual weights of eight indicators and the integrated flood vulnerability index for Syracuse. The map of this index showed that the floodplain area near Onondaga Creek has a higher vulnerability index than other areas of the city, and the degree of vulnerability is strongly related to the distance to Onondaga Creek. The second part focused on flood damage assessment of the projected 500-year flood event in Syracuse. Flood inundation during this event could affect local residents, buildings, and the environment. Therefore, these three factors were considered in the damage assessment. Based on the commonly used category of flood damages, including tangible, intangible, direct, and indirect, the flood damage of Syracuse was divided into loss of buildings, loss of population, and loss of environment (represented by vegetation in this thesis). The results showed that the city\u27s center would have the highest damage rate for buildings, and a total of 326 buildings will be severely damaged by more than 80%. A total of 169560 m2 of the green land would be inundated, and the total damage to the forest and green land is about $170,000. Furthermore, the simulated 500-Year flood would result in the loss of life for about 900 people. The third part involved a flood evacuation design for this 500-year flood event in Syracuse. Communities near Onondaga Creek were assigned designated evacuation shelters based on the accessibility and distance to the shelters. The shortest available evacuation routes were calculated. Also, the distribution of evacuation shelters and estimated population were discussed, which revealed the spatial relationship between population and the distribution of shelters. Some communities would have a shortage of shelters suggesting that the current distribution of shelters is inadequate. Suggested locations for five new shelters were provided in the central downtown area with a large population and distributed along the western bank of Onondaga Creek. This research offered a first-approximate flood hazard assessment that may lead to more a sophisticated flood hazard assessment in the future. It also provided science-based guidelines for city authorities to refer to in practical flood management