Role of Watershed Geomorphic Characteristics on Flooding in Indiana, United States

Despite the documented evidence of geomorphic characteristics on flooding, an understanding of the relative effects of the geomorphic characteristics on flooding remains elusive. The objective of this study is to investigate the relationship between flooding and geomorphic characteristics in Indiana, United States, by using data at 94 streamflow gauging stations. The flood magnitude as determined through the flash flood index is categorized into three groups, including moderate, extreme, and severe. The flood in each group is then related to geomorphic characteristics, including topography, morphometry, slope, land use, soil, channel network, and aspect through stepwise regression. Results show that extreme flooding is most affected by watershed morphometry, particularly watershed length, whereas severe flooding is most affected by watershed slope and land use type. The methodology used in this study also highlights that the stronger the severity of flooding, the more it is explained by geomorphic characteristics. Additional investigation of the effect of land cover type and watershed size using the Kruskal-Wallis rank test shows that land cover type affects flooding occurrence despite its relatively role is relatively smaller compared with other variables. Finally, flooding is more affected by watershed length than watershed area for the watersheds included in this study. (C) 2015 American Society of Civil Engineers.