A comparison of storm hydrographs from small urban watersheds with different land use patterns in Baton Rouge

Statistics gathered by FEMA indicate that nine of ten federal disasters are related to flooding. Research has demonstrated that increases in flooding can be contributed to urbanization or the construction of new residential and commercial developments (Anderson, 1970; Arnold & Gibbons, 1996; Putnam, 1972). New development has two main problems associated with it. First is the increase in impervious surfaces due to new parking lots, buildings, and streets (Booth & Leavitt, 1999; Seaburn, 1969). Second is the elimination of natural vegetation, which reduces evapotranspiration and lowers the soil’s ability to absorb precipitation (Hewlett, 1982). This study first demonstrates the relationship between land use and land cover characteristics associated with urbanization to hydrograph statistics, specifically time to rise and total rise. Secondly to create predictive models of watershed behavior based on these measures. Time to rise is the time between the inception of a storm and the initial rise of stream stage. Total rise is the total rise in stage to its peak, during the entire storm. This study represents a new geospatial approach for studying these relationships. The study first established a GIS database of land use and land cover characteristics. The second phase performed regression analyses of the hydrograph response variables with the land use and land cover characteristics as independent variables. There were statistically significant relationships between residential development, commercial development and roads with the response variables, time to rise and total rise. As development increases time to rise decreased and total rise increased. The percentage of forest land use, land maintained as contiguous forest, was correlated with total rise. As the percentage of forest land use increased the total rise decreased. This study demonstrates some univariate models that show direct relationships between land use and land cover characteristic and hydrograph response