Expectations for Increases in the Magnitude and Frequency of Peakflows with Future Climate Change: the Need to Validate Study Approaches

Abstract:

Atmospheric moisture holding capacity increases with increased air temperature suggesting that the magnitude of large precipitation events will increase with future climate warming. Several studies have shown an increasing trend in the magnitude of large storms, but wide regional variation is also apparent. These results suggest that future patterns will be complex and not readily predictable at regional scales. Additionally, factors such as soil moisture and snowpack play a large role in runoff response indicating that large storms do not equate to large floods. Large precipitation events and high flows have become more frequent in the northeastern US during the 20^th century, suggesting a need for approaches to make projections of future regional flood peaks. One approach is space-for-time substitution applied to regressions that predict the magnitude of peakflows and include predictive variables based on land cover, geomorphology, and climate. Future precipitation estimates are substituted into these regressions yielding estimates of future peakflows. This approach was applied in New York and results indicate a general increase in peak flow magnitudes of about 10% to 20% by the end of the 21^st century. These results are available through a web-based application that provides peakflow estimates for any statewide river that meets a set of criteria. However, this application does not provide uncertainty bounds nor was the space-for-time approach validated. Considering the increasing application of similar space-for-time approaches, further validation is warranted including comparisons with other approaches that estimate the likely effects of climate change on future peakflows.