Ground-Level Rainfall Variation in Jefferson County, Kentucky

In urban hydrology, accurate temporal and spatial rainfall observations are a key factor for managing urban hydrologic systems and stormwater runoff, particularly in the current era of higher variability in recent rainfall events. To study this issue, rain gauge data from a ground-based rainfall measurement network operated by the local stormwater management agency, Metropolitan Sewer District (MSD), in Jefferson County, Kentucky is evaluated. Rainfall spatial characteristics are evaluated through correlation spectrum by distance indicating a spatial rainfall variation concave relationship. The correlations at a 5-km distance are [0.63, 0.74, 0.80, and 0.86] for temporal resolutions of (15min, 30min, 1h, and 3h), respectively. A decreasing correlation with increased rainfall intensity is observed at temporal resolutions less than 1h, and correlation increases at higher rainfall intensities and temporal resolution coarser than 1h. This case study provides a context for the use of recent historical information to guide urban stormwater management planning through rain gauge deployment and detection of regional rainfall characteristics. (C) 2016 American Society of Civil Engineers.