Runoff increases due to urbanization in a semi-arid city

In the southwestern United States, water is available in the form of discontinuous seasonal precipitation events associated with the North American Monsoon and the winter rainy season (Gallo et al., 2012). These wet seasons, particularly the North American Monsoon, are characterized by heavy rainfall events that lead to urban flooding issues, separated by periods of dryness. The rapid nature of change (hydrographs on the order of minute) combined with intense spatial heterogeneity in rainfall patterns leads to unique temporal and spatial data needs and considerations to assess urban flooding issues and associated solutions such as green stormwater infrastructure.

Due to the spatial heterogeneity of stormwater infrastructure within a single municipality, urban flooding issues observed in one watershed may not be applicable to others due to varying watershed size, types of stormwater infrastructure, and contributing land cover. Urban hydrological data has been collected in the city of Tucson, Arizona to assess the variability in runoff volumes and flood hydrographs across multiple urban ephemeral washes and compared across watersheds with similar and varying contributing area and contributing land use cover. Analyses show that as urbanization increases, runoff frequency and duration increase compared to undeveloped watersheds.