Spatiotemporal Variation of Annual Maximum Precipitation in East Coastal Virginia over the Past Half Century

Maximum precipitation is commonly used to size hydraulic structures (e.g., storm sewers) in practice but great variance exists between locations and annually at a given location. Understanding this spatiotemporal variation is necessary for accurate rainfall predictions but remains incomplete in most regions, including the state of Virginia. The objective of this study was to fill this information gap for Virginia using data collected from 57 rain gauges. This study used modified Mann-Kendall, Sen's slope, and linear regression that considers nonstationary resulting from climate change to detect possible step changes and temporal trends of maximum annual precipitation at various time intervals. Global Moran's I and local indicator of spatial association (LISA) have been applied to examine the spatial autocorrelations and clusters. The results indicated that the annual maximum durational intensities exhibited no step change but had a significant (α = 0.05) decreasing trend at most of the rain gauges. Most significant trends occurred in the Northern and Central Mountain climatic divisions. The intensities of a duration of 2hr or longer were found to have a significant positive spatial autocorrelation within the climate divisions of Northern and Tidewater. The intensities at the gauges within a climatic division of interest tended to be positively correlated. These results will help prevent over- or under-committing resources in the design and construction of future flood control measures in the state of Virginia and provide a method framework from which the spatiotemporal patterns in other regions may be studied.