Flood Nonstationarity in the Southeast and Mid-Atlantic Regions of the United States

AbstractA case study examining aspects of nonstationarity in the estimation of flood magnitudes in the Southeast and mid-Atlantic United States is presented here. The focus is on challenges posed by changes in the number and location of stream gauges over time to assess climate variability and land-use land-cover (LULC) change impacts. The study shows that statistical outliers are spatially aligned with LULC change from urbanization independently of time period and record length across the region with substantial increases (>30%) in the magnitude of the 25-year and 100-year events since 1950. Large amplification (>10) of the ratio of flood magnitude to the mean annual flood was detected in expanding urban areas, but only systematically for the 100-year event, suggesting that existing infrastructure constrains the sensitivity of flood response for events below applied engineering design criteria. Overall, annual streamflows do not exhibit statistically significant trends (98% cfl), except for positive tren...