Exploring the possibilities of improving flood frequency analysis in the West by incorporating paleohydrologic reconstructions
Presently flood frequency analyses (FFA) for dams and related infrastructure are based on representative stream gage data coupled with site-specific paleoflood studies. This methodology is documented in the guidelines for determining flood flow frequency - Bulletin 17C (England et al., 2018).
Broadly speaking, gage data for a specific site are typically available in the order of 100 years, paleoflood information is in the order of 10,000 years (e.g., Ely et al., 1993; Harden, 2007; Nott et al., 1996), and reconstructed streamflows from tree-rings provides an opportunity to bridge this data gap. Reconstructions from tree-rings across the West can provide nearly multi-century long streamflow record (e.g., Rice et al., 2009 reference to TreeFlow) and can likely be used to inform site-specific FFA. Redmond et al. (2002) describes the applicability of tree-ring records (dendrochronologic records – time series of tree ring properties) in the context of flood analysis, and states that under specific circumstances, tree-ring information can provide useful and even invaluable input for flood studies (especially, large floods).
Thus, in the literature, there is a recognition that dendrochronology records can be used in FFA. However, to the best of our knowledge, to date, there has not been a single application of incorporating reconstructed streamflow in FFA. There is a wealth of hydroclimate information contained in tree-ring chronologies across the western United States (West) and in the reconstructed streamflows derived from these chronologies. Also, such streamflow reconstruction data can be readily accessed through well-established web resources, for example, TreeFlow (https://www.treeflow.info/); tree-ring chronology data can be accessed through the International Tree-Ring Data Bank's (ITRDB; https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/tree-ring) web archive.
Based on the discussion of the availability of tree-ring chronology data
Need and Benefit
Gage data for a specific site are typically available in the order of 100 years, paleoflood information is in the order of 10,000 years, and reconstructed streamflows from tree-rings provides an opportunity to bridge this data gap by providing nearly multi-century long streamflow record. However, streamflow reconstructions don't appear to be used in developing flood frequency analysis. Why? The literature acknowledges it's applicability, tree-ring chronologies and streamflow reconstructions are readily available, and thus we want to explore the possibilities of improving flood frequency analysis in the West by incorporating these data sets. Understand conditions under which they might be applicable, and how it might complement paleoflood information used in current FFA practice.
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